text stringlengths 26 3.6k | page_title stringlengths 1 71 | source stringclasses 1
value | token_count int64 10 512 | id stringlengths 2 8 | url stringlengths 31 117 | topic stringclasses 4
values | section stringlengths 4 49 ⌀ | sublist stringclasses 9
values |
|---|---|---|---|---|---|---|---|---|
Hyperactive apoptosis
On the other hand, loss of control of cell death (resulting in excess apoptosis) can lead to neurodegenerative diseases, hematologic diseases, and tissue damage. Neurons that rely on mitochondrial respiration undergo apoptosis in neurodegenerative diseases such as Alzheimer's and Parkinson's. (an observation known as the "Inverse Warburg hypothesis"). Moreover, there is an inverse epidemiological comorbidity between neurodegenerative diseases and cancer. The progression of HIV is directly linked to excess, unregulated apoptosis. In a healthy individual, the number of CD4+ lymphocytes is in balance with the cells generated by the bone marrow; however, in HIV-positive patients, this balance is lost due to an inability of the bone marrow to regenerate CD4+ cells. In the case of HIV, CD4+ lymphocytes die at an accelerated rate through uncontrolled apoptosis, when stimulated.
At the molecular level, hyperactive apoptosis can be caused by defects in signaling pathways that regulate the Bcl-2 family proteins. Increased expression of apoptotic proteins such as BIM, or their decreased proteolysis, leads to cell death and can cause a number of pathologies, depending on the cells where excessive activity of BIM occurs. Cancer cells can escape apoptosis through mechanisms that suppress BIM expression or by increased proteolysis of BIM.
Treatments
Treatments aiming to inhibit works to block specific caspases. Finally, the Akt protein kinase promotes cell survival through two pathways. Akt phosphorylates and inhibits Bad (a Bcl-2 family member), causing Bad to interact with the 14-3-3 scaffold, resulting in Bcl dissociation and thus cell survival. Akt also activates IKKα, which leads to NF-κB activation and cell survival. Active NF-κB induces the expression of anti-apoptotic genes such as Bcl-2, resulting in inhibition of apoptosis. NF-κB has been found to play both an antiapoptotic role and a proapoptotic role depending on the stimuli utilized and the cell type. | Apoptosis | Wikipedia | 478 | 2457 | https://en.wikipedia.org/wiki/Apoptosis | Biology and health sciences | Cell processes | Biology |
HIV progression
The progression of the human immunodeficiency virus infection into AIDS is due primarily to the depletion of CD4+ T-helper lymphocytes in a manner that is too rapid for the body's bone marrow to replenish the cells, leading to a compromised immune system. One of the mechanisms by which T-helper cells are depleted is apoptosis, which results from a series of biochemical pathways:
HIV enzymes deactivate anti-apoptotic Bcl-2. This does not directly cause cell death but primes the cell for apoptosis should the appropriate signal be received. In parallel, these enzymes activate proapoptotic procaspase-8, which does directly activate the mitochondrial events of apoptosis.
HIV may increase the level of cellular proteins that prompt Fas-mediated apoptosis.
HIV proteins decrease the amount of CD4 glycoprotein marker present on the cell membrane.
Released viral particles and proteins present in extracellular fluid are able to induce apoptosis in nearby "bystander" T helper cells.
HIV decreases the production of molecules involved in marking the cell for apoptosis, giving the virus time to replicate and continue releasing apoptotic agents and virions into the surrounding tissue.
The infected CD4+ cell may also receive the death signal from a cytotoxic T cell.
Cells may also die as direct consequences of viral infections. HIV-1 expression induces tubular cell G2/M arrest and apoptosis. The progression from HIV to AIDS is not immediate or even necessarily rapid; HIV's cytotoxic activity toward CD4+ lymphocytes is classified as AIDS once a given patient's CD4+ cell count falls below 200. | Apoptosis | Wikipedia | 368 | 2457 | https://en.wikipedia.org/wiki/Apoptosis | Biology and health sciences | Cell processes | Biology |
Researchers from Kumamoto University in Japan have developed a new method to eradicate HIV in viral reservoir cells, named "Lock-in and apoptosis." Using the synthesized compound Heptanoylphosphatidyl L-Inositol Pentakisphophate (or L-Hippo) to bind strongly to the HIV protein PR55Gag, they were able to suppress viral budding. By suppressing viral budding, the researchers were able to trap the HIV virus in the cell and allow for the cell to undergo apoptosis (natural cell death). Associate Professor Mikako Fujita has stated that the approach is not yet available to HIV patients because the research team has to conduct further research on combining the drug therapy that currently exists with this "Lock-in and apoptosis" approach to lead to complete recovery from HIV.
Viral infection
Viral induction of apoptosis occurs when one or several cells of a living organism are infected with a virus, leading to cell death. Cell death in organisms is necessary for the normal development of cells and the cell cycle maturation. It is also important in maintaining the regular functions and activities of cells. | Apoptosis | Wikipedia | 240 | 2457 | https://en.wikipedia.org/wiki/Apoptosis | Biology and health sciences | Cell processes | Biology |
Viruses can trigger apoptosis of infected cells via a range of mechanisms including:
Receptor binding
Activation of protein kinase R (PKR)
Interaction with p53
Expression of viral proteins coupled to MHC proteins on the surface of the infected cell, allowing recognition by cells of the immune system (such as natural killer and cytotoxic T cells) that then induce the infected cell to undergo apoptosis.
Canine distemper virus (CDV) is known to cause apoptosis in central nervous system and lymphoid tissue of infected dogs in vivo and in vitro.
Apoptosis caused by CDV is typically induced via the extrinsic pathway, which activates caspases that disrupt cellular function and eventually leads to the cells death. In normal cells, CDV activates caspase-8 first, which works as the initiator protein followed by the executioner protein caspase-3. However, apoptosis induced by CDV in HeLa cells does not involve the initiator protein caspase-8. HeLa cell apoptosis caused by CDV follows a different mechanism than that in vero cell lines. This change in the caspase cascade suggests CDV induces apoptosis via the intrinsic pathway, excluding the need for the initiator caspase-8. The executioner protein is instead activated by the internal stimuli caused by viral infection not a caspase cascade.
The Oropouche virus (OROV) is found in the family Bunyaviridae. The study of apoptosis brought on by Bunyaviridae was initiated in 1996, when it was observed that apoptosis was induced by the La Crosse virus into the kidney cells of baby hamsters and into the brains of baby mice.
OROV is a disease that is transmitted between humans by the biting midge (Culicoides paraensis). It is referred to as a zoonotic arbovirus and causes febrile illness, characterized by the onset of a sudden fever known as Oropouche fever.
The Oropouche virus also causes disruption in cultured cells – cells that are cultivated in distinct and specific conditions. An example of this can be seen in HeLa cells, whereby the cells begin to degenerate shortly after they are infected. | Apoptosis | Wikipedia | 470 | 2457 | https://en.wikipedia.org/wiki/Apoptosis | Biology and health sciences | Cell processes | Biology |
With the use of gel electrophoresis, it can be observed that OROV causes DNA fragmentation in HeLa cells. It can be interpreted by counting, measuring, and analyzing the cells of the Sub/G1 cell population. When HeLA cells are infected with OROV, the cytochrome C is released from the membrane of the mitochondria, into the cytosol of the cells. This type of interaction shows that apoptosis is activated via an intrinsic pathway.
In order for apoptosis to occur within OROV, viral uncoating, viral internalization, along with the replication of cells is necessary. Apoptosis in some viruses is activated by extracellular stimuli. However, studies have demonstrated that the OROV infection causes apoptosis to be activated through intracellular stimuli and involves the mitochondria.
Many viruses encode proteins that can inhibit apoptosis. Several viruses encode viral homologs of Bcl-2. These homologs can inhibit proapoptotic proteins such as BAX and BAK, which are essential for the activation of apoptosis. Examples of viral Bcl-2 proteins include the Epstein-Barr virus BHRF1 protein and the adenovirus E1B 19K protein. Some viruses express caspase inhibitors that inhibit caspase activity and an example is the CrmA protein of cowpox viruses. Whilst a number of viruses can block the effects of TNF and Fas. For example, the M-T2 protein of myxoma viruses can bind TNF preventing it from binding the TNF receptor and inducing a response. Furthermore, many viruses express p53 inhibitors that can bind p53 and inhibit its transcriptional transactivation activity. As a consequence, p53 cannot induce apoptosis, since it cannot induce the expression of proapoptotic proteins. The adenovirus E1B-55K protein and the hepatitis B virus HBx protein are examples of viral proteins that can perform such a function.
Viruses can remain intact from apoptosis in particular in the latter stages of infection. They can be exported in the apoptotic bodies that pinch off from the surface of the dying cell, and the fact that they are engulfed by phagocytes prevents the initiation of a host response. This favours the spread of the virus. Prions can cause apoptosis in neurons. | Apoptosis | Wikipedia | 491 | 2457 | https://en.wikipedia.org/wiki/Apoptosis | Biology and health sciences | Cell processes | Biology |
Plants
Programmed cell death in plants has a number of molecular similarities to that of animal apoptosis, but it also has differences, notable ones being the presence of a cell wall and the lack of an immune system that removes the pieces of the dead cell. Instead of an immune response, the dying cell synthesizes substances to break itself down and places them in a vacuole that ruptures as the cell dies. Additionally, plants do not contain phagocytic cells, which are essential in the process of breaking down and removing apoptotic bodies. Whether this whole process resembles animal apoptosis closely enough to warrant using the name apoptosis (as opposed to the more general programmed cell death) is unclear.
Caspase-independent apoptosis
The characterization of the caspases allowed the development of caspase inhibitors, which can be used to determine whether a cellular process involves active caspases. Using these inhibitors it was discovered that cells can die while displaying a morphology similar to apoptosis without caspase activation. Later studies linked this phenomenon to the release of AIF (apoptosis-inducing factor) from the mitochondria and its translocation into the nucleus mediated by its NLS (nuclear localization signal). Inside the mitochondria, AIF is anchored to the inner membrane. In order to be released, the protein is cleaved by a calcium-dependent calpain protease. | Apoptosis | Wikipedia | 297 | 2457 | https://en.wikipedia.org/wiki/Apoptosis | Biology and health sciences | Cell processes | Biology |
The aurochs (Bos primigenius) ( or , plural aurochs or aurochsen) is an extinct species of bovine, considered to be the wild ancestor of modern domestic cattle. With a shoulder height of up to in bulls and in cows, it was one of the largest herbivores in the Holocene; it had massive elongated and broad horns that reached in length.
The aurochs was part of the Pleistocene megafauna. It probably evolved in Asia and migrated west and north during warm interglacial periods. The oldest-known aurochs fossils date to the Middle Pleistocene. The species had an expansive range spanning from Western Europe and North Africa to the Indian subcontinent and East Asia. The distribution of the aurochs progressively contracted during the Holocene due to habitat loss and hunting, with the last known individual dying in the Jaktorów forest in Poland in 1627.
There is a long history of interaction between aurochs and humans, including archaic humans like Neanderthals. The aurochs is depicted in Paleolithic cave paintings, Neolithic petroglyphs, Ancient Egyptian reliefs and Bronze Age figurines. It symbolised power, sexual potency and prowess in religions of the ancient Near East. Its horns were used in votive offerings, as trophies and drinking horns.
Two aurochs domestication events occurred during the Neolithic Revolution. One gave rise to the domestic taurine cattle (Bos taurus) in the Fertile Crescent in the Near East that was introduced to Europe via the Balkans and the coast of the Mediterranean Sea. Hybridisation between aurochs and early domestic cattle occurred during the early Holocene. Domestication of the Indian aurochs led to the zebu cattle (Bos indicus) that hybridised with early taurine cattle in the Near East about 4,000 years ago. Some modern cattle breeds exhibit features reminiscent of the aurochs, such as the dark colour and light eel stripe along the back of bulls, the lighter colour of cows, or an aurochs-like horn shape.
Etymology
Both "aur" and "ur" are Germanic or Celtic words meaning "wild ox".
In Old High German, this word was compounded with ohso ('ox') to ūrohso, which became the early modern Aurochs. The Latin word "urus" was used for wild ox from the Gallic Wars onwards. | Aurochs | Wikipedia | 500 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
The use of the plural form in English is a direct parallel of the German plural Ochsen and recreates the same distinction by analogy as English singular ox and plural oxen, although aurochs may stand for both the singular and the plural term; both are attested.
Taxonomy and evolution
The scientific name Bos taurus was introduced by Carl Linnaeus in 1758 for feral cattle in Poland.
The scientific name Bos primigenius was proposed for the aurochs by Ludwig Heinrich Bojanus who described the skeletal differences between the aurochs and domestic cattle in 1825, published in 1827. The name Bos namadicus was used by Hugh Falconer in 1859 for cattle fossils found in Nerbudda deposits.
Bos primigenius mauritanicus was coined by Philippe Thomas in 1881 who described fossils found in deposits near Oued Seguen west of Constantine, Algeria.
In 2003, the International Commission on Zoological Nomenclature placed Bos primigenius on the Official List of Specific Names in Zoology and thereby recognized the validity of this name for a wild species.
Subspecies
Three aurochs subspecies have traditionally been recognised to have existed in historical times:
The Eurasian aurochs (B. p. primigenius) was part of the Pleistocene megafauna in Eurasia and survived until the 17th century in Eastern Europe.
The Indian aurochs (B. p. namadicus) lived on the Indian subcontinent.
The North African aurochs (B. p. mauritanicus) lived north of the Sahara. This subspecies has also been called B. p. opisthonomus.
In the 21st century, Chinese geneticists published mitochondrial DNA evidence supporting that Eurasian aurochs populations from northern China were genetically isolated for large stretches of the Pleistocene, and as a result distinctive enough to be considered a separate subspecies, the East Asian aurochs (B. p. sinensis), even if the animals were not morphologically distinct.
At least two dwarf subspecies of aurochs developed in Mediterranean islands as a result of sea level changes during the Pleistocene:
B. p. siciliae on the Italian island of Sicily.
B. p. thrinacius on the Greek island of Kythira. | Aurochs | Wikipedia | 454 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
Evolution
Calibrations using fossils of 16 Bovidae species indicate that the Bovini tribe evolved about . The Bos and Bison genetic lineages are estimated to have genetically diverged from the Bovini about . The following cladogram shows the phylogenetic relationships of the aurochs based on analysis of nuclear and mitochondrial genomes in the Bovini tribe:
The cold Pliocene climate caused an extension of open grassland, which enabled the evolution of large grazers. The origin of the aurochs is unclear, with authors suggesting either an African or Asian origin for the species. Bos acutifrons is considered to be a possible ancestor of the aurochs, of which a fossil skull was excavated in the Sivalik Hills in India that dates to the Early Pleistocene about .
An aurochs skull excavated in Tunisia's Kef Governorate from early Middle Pleistocene strata dating about is the oldest well-dated fossil specimen to date. The authors of the study proposed that Bos might have evolved in Africa and migrated to Eurasia during the Middle Pleistocene. Middle Pleistocene aurochs fossils were also excavated in a Saharan erg in the Hoggar Mountains.
Fossils of the Indian subspecies (Bos primigenius namadicus) were excavated in alluvial deposits in South India dating to the Middle Pleistocene. Remains of aurochs are common in Late Pleistocene sites across the Indian subcontinent.
The earliest fossils in Europe date to the Middle Pleistocene. One site widely historically suggested to represent the first appearance of aurochs in Europe was the Notarchirico site in southern Italy, dating around 600,000 years ago, however a 2024 re-examination of the site found that presence of aurochs at the locality was unsupported, with the oldest records of aurochs now placed at the Ponte Molle site in central Italy, dating to around 550-450,000 years ago. Aurochs were present in Britain by Marine Isotope Stage 11 ~400,000 years ago.
The earliest remains aurochs in East Asia are uncertain, but may date to the late Middle Pleistocene.
Late Pleistocene aurochs fossils were found in Affad 23 in Sudan dating to 50,000 years ago when the climate in this region was more humid than during the African humid period.
Following the most recent deglaciation, the range of the aurochs expanded into Denmark and southern Sweden at the beginning of the Holocene, around 12-11,000 years ago.
Description | Aurochs | Wikipedia | 508 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
According to a 16th-century description by Sigismund von Herberstein, the aurochs was pitch-black with a grey streak along the back; his wood carving made in 1556 was based on a culled aurochs, which he had received in Mazovia. In 1827, Charles Hamilton Smith published an image of an aurochs that was based on an oil painting that he had purchased from a merchant in Augsburg, which is thought to have been made in the early 16th century. This painting is thought to have shown an aurochs, although some authors suggested it may have shown a hybrid between an aurochs and domestic cattle, or a Polish steer. Contemporary reconstructions of the aurochs are based on skeletons and the information derived from contemporaneous artistic depictions and historic descriptions of the animal.
Coat colour
Remains of aurochs hair were not known until the early 1980s. Depictions show that the North African aurochs may have had a light saddle marking on its back. Calves were probably born with a chestnut colour, and young bulls changed to black with a white eel stripe running down the spine, while cows retained a reddish-brown colour. Both sexes had a light-coloured muzzle, but evidence for variation in coat colour does not exist. Egyptian grave paintings show cattle with a reddish-brown coat colour in both sexes, with a light saddle, but the horn shape of these suggest that they may depict domesticated cattle.
Many primitive cattle breeds, particularly those from Southern Europe, display similar coat colours to the aurochs, including the black colour in bulls with a light eel stripe, a pale mouth, and similar sexual dimorphism in colour. A feature often attributed to the aurochs is blond forehead hairs. According to historical descriptions of the aurochs, it had long and curly forehead hair, but none mentions a certain colour. Although the colour is present in a variety of primitive cattle breeds, it is probably a discolouration that appeared after domestication.
Body shape | Aurochs | Wikipedia | 406 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
The proportions and body shape of the aurochs were strikingly different from many modern cattle breeds. For example, the legs were considerably longer and more slender, resulting in a shoulder height that nearly equalled the trunk length. The skull, carrying the large horns, was substantially larger and more elongated than in most cattle breeds. As in other wild bovines, the body shape of the aurochs was athletic, and especially in bulls, showed a strongly expressed neck and shoulder musculature. Therefore, the fore hand was larger than the rear, similar to the wisent, but unlike many domesticated cattle. Even in carrying cows, the udder was small and hardly visible from the side; this feature is equal to that of other wild bovines.
Size
The aurochs was one of the largest herbivores in Holocene Europe. The size of an aurochs appears to have varied by region, with larger specimens in northern Europe than farther south. Aurochs in Denmark and Germany ranged in height at the shoulders between in bulls and in cows, while aurochs bulls in Hungary reached .
The African aurochs was similar in size to the European aurochs in the Pleistocene, but declined in size during the transition to the Holocene; it may have also varied in size geographically.
The body mass of aurochs appears to have shown some variability. Some individuals reached around , whereas those from the late Middle Pleistocene are estimated to have weighed up to . The aurochs exhibited considerable sexual dimorphism in the size of males and females.
Horns
The horns were massive, reaching in length and between in diameter. Its horns grew from the skull at a 60-degree angle to the muzzle facing forwards and were curved in three directions, namely upwards and outwards at the base, then swinging forwards and inwards, then inwards and upwards. The curvature of bull horns was more strongly expressed than horns of cows. The basal circumference of horn cores reached in the largest Chinese specimen and in a French specimen. Some cattle breeds still show horn shapes similar to that of the aurochs, such as the Spanish fighting bull, and occasionally also individuals of derived breeds. | Aurochs | Wikipedia | 447 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
Genetics
A well-preserved aurochs bone yielded sufficient mitochondrial DNA for a sequence analysis in 2010, which showed that its genome consists of 16,338 base pairs. Further studies using the aurochs whole genome sequence have identified candidate microRNA-regulated domestication genes. A comprehensive sequence analysis of Late Pleistocene and Holocene aurochs published in 2024 suggested that Indian aurochs (represented by modern zebu cattle) were the most genetically divergent aurochs population, having diverged from other aurochs around 300–166,000 years ago, with other aurochs populations spanning Europe and the Middle East to East Asia sharing much more recent common ancestry within the last 100,000 years. Late Pleistocene European aurochs were found to have a small (~3%) ancestry component from a divergent lineage that split prior to the divergence of Indian and other aurochs, suggested to be residual from earlier European aurochs populations. Towards the end of the Late Pleistocene, European aurochs experienced considerable gene flow from Middle Eastern aurochs. European Holocene aurochs primarily descend from those that were present in the Iberian Peninsula during the Last Glacial Maximum, with the Holocene also seeing mixing between previously isolated aurochs populations.
Distribution and habitat
The aurochs was widely distributed in North Africa, Mesopotamia, and throughout Europe to the Pontic–Caspian steppe, Caucasus and Western Siberia in the west and to the Gulf of Finland and Lake Ladoga in the north.
Fossil horns attributed to the aurochs were found in Late Pleistocene deposits at an elevation of on the eastern margin of the Tibetan plateau close to the Heihe River in Zoigê County that date to about 26,620±600 years BP. Most fossils in China were found in plains below in Heilongjiang, Yushu, Jilin, northeastern Manchuria, Inner Mongolia, near Beijing, Yangyuan County in Hebei province, Datong and Dingcun in Shanxi province, Huan County in Gansu and in Guizhou provinces. Ancient DNA in aurochs fossils found in Northeast China indicate that the aurochs survived in the region until at least 5,000 years BP. Fossils were also excavated on the Korean Peninsula, and in the Japanese archipelago.
During warm interglacial periods the aurochs was widespread across Europe, but during glacial periods retreated into southern refugia in the Iberian, Italian and Balkan peninsulas. | Aurochs | Wikipedia | 499 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
Landscapes in Europe probably consisted of dense forests throughout much of the last few thousand years. The aurochs is likely to have used riparian forests and wetlands along lakes. Analysis of specimens found in Britain suggests that aurochs preferred inhabiting low lying relatively flat landscapes. Pollen of mostly small shrubs found in fossiliferous sediments with aurochs remains in China indicate that it preferred temperate grassy plains or grasslands bordering woodlands. It may have also lived in open grasslands. In the warm Atlantic period of the Holocene, it was restricted to remaining open country and forest margins, where competition with livestock and humans gradually increased leading to a successive decline of the aurochs.
Behaviour and ecology
Aurochs formed small herds mainly in winter, but typically lived singly or in smaller groups during the summer. If aurochs had social behaviour similar to their descendants, social status would have been gained through displays and fights, in which both cows and bulls engaged. Since it has a hypsodont jaw, it has been suggested to have been a grazer, with a food selection very similar to domesticated cattle feeding on grass, twigs and acorns. Mesowear analysis of Holocene Danish aurochs premolar teeth indicates that it changed from an abrasion-dominated grazer in the Danish Preboreal to a mixed feeder in the Boreal, Atlantic and Subboreal periods. Dental microwear and mesowear analysis of specimens from the Pleistocene of Britain has found these aurochs had mixed feeding to browsing diets, rather than being strict grazers. | Aurochs | Wikipedia | 319 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
Mating season was in September, and calves were born in spring. Rutting bulls had violent fights, and evidence from the Jaktorów forest shows that they were fully capable of mortally wounding one another. In autumn, aurochs fed for the winter, gaining weight and possessing a shinier coat than during the rest of the year. Calves stayed with their mothers until they were strong enough to join and keep up with the herd on the feeding grounds. Aurochs calves would have been vulnerable to predation by grey wolves (Canis lupus) and brown bears (Ursus arctos), while the immense size and strength of healthy adult aurochs meant they likely did not need to fear most predators. According to historical descriptions, the aurochs was swift despite its build, could be very aggressive if provoked, and was not generally fearful of humans. In Middle Pleistocene Europe, aurochs were likely predated upon by the "European jaguar" Panthera gombaszoegensis and the scimitar toothed-cat (Homotherium latidens), with evidence for the consumption of aurochs by cave hyenas (Crocuta (Crocuta) spelaea) having been found from Late Pleistocene Italy. The lion (Panthera leo), tiger (Panthera tigris) and wolf are thought to have been the aurochs main predators during the Holocene.
During interglacial periods in the Middle Pleistocene and early Late Pleistocene in Europe, the aurochs occurred alongside other large temperate adapted megafauna species, including the straight-tusked elephant (Palaeoloxodon antiquus), Merck's rhinoceros (Stephanorhinus kirchbergensis), the narrow-nosed rhinoceros, (Stephanorhinus hemitoechus) and the Irish elk/giant deer (Megaloceros giganteus).
Relationship with humans
In Asia | Aurochs | Wikipedia | 400 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
Acheulean layers in Hunasagi on India's southern Deccan Plateau yielded aurochs bones with cut marks. An aurochs bone with cut marks induced with flint was found in a Middle Paleolithic layer at the Nesher Ramla Homo site in Israel; it was dated to Marine Isotope Stage 5 about 120,000 years ago. An archaeological excavation in Israel found traces of a feast held by the Natufian culture around 12,000 years BP, in which three aurochs were eaten. This appears to be an uncommon occurrence in the culture and was held in conjunction with the burial of an older woman, presumably of some social status. Petroglyphs depicting aurochs in Gobustan Rock Art in Azerbaijan date to the Upper Paleolithic to Neolithic periods.
Aurochs bones and skulls found at the settlements of Mureybet, Hallan Çemi and Çayönü indicate that people stored and shared food in the Pre-Pottery Neolithic B culture.
Remains of an aurochs were also found in a necropolis in Sidon, Lebanon, dating to around 3,700 years BP; the aurochs was buried together with numerous animals, a few human bones and foods.
Seals dating to the Indus Valley civilisation found in Harappa and Mohenjo-daro show an animal with curved horns like an aurochs. Aurochs figurines were made by the Maykop culture in the Western Caucasus.
The aurochs is denoted in the Akkadian words rīmu and rēmu, both used in the context of hunts by rulers such as Naram-Sin of Akkad, Tiglath-Pileser I and Shalmaneser III; in Mesopotamia, it symbolised power and sexual potency, was an epithet of the gods Enlil and Shamash, denoted prowess as an epithet of the king Sennacherib and the hero Gilgamesh. Wild bulls are frequently referred to in Ugaritic texts as hunted by and sacrificed to the god Baal. An aurochs is depicted on Babylon's Ishtar Gate, constructed in the 6th century BC. | Aurochs | Wikipedia | 435 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
In Africa
Petroglyphs depicting aurochs found in Qurta in the upper Nile valley were dated to the Late Pleistocene about 19–15,000 years BP using luminescence dating and are the oldest engravings found to date in Africa. Aurochs are part of hunting scenes in reliefs in a tomb at Thebes, Egypt dating to the 20th century BC, and in the mortuary temple of Ramesses III at Medinet Habu dating to around 1175 BC. The latter is the youngest depiction of aurochs in Ancient Egyptian art to date.
In Europe
Evidence has been found for the butchery of aurochs by archaic humans in Europe during the Middle Palaeolithic, such as the Biache-Saint-Vaast site in northern France dating to around 240,000 years ago, where bones of aurochs have been found burnt by fire and with cut marks, thought to have been created by Neanderthals. At the late Middle Palaeolithic Cueva Des-Cubierta site in Spain, Neanderthals are proposed to have kept the skulls of aurochs as hunting trophies. | Aurochs | Wikipedia | 231 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
The aurochs is widely represented in Upper Paleolithic cave paintings in the Chauvet and Lascaux caves in southern France dating to 36,000 and 21,000 years BP, respectively.
Two Paleolithic rock engravings in the Calabrian Romito Cave depict an aurochs.
Palaeolithic engravings showing aurochs were also found in the Grotta del Genovese on the Italian island of Levanzo.
Upper Paleolithic rock engravings and paintings depicting the aurochs were also found in caves on the Iberian Peninsula dating from the Gravettian to the Magdalenian cultures.
Aurochs bones with chop and cut marks were found at various Mesolithic hunting and butchering sites in France, Luxemburg, Germany, the Netherlands, England and Denmark. Aurochs bones were also found in Mesolithic settlements by the Narva and Emajõgi rivers in Estonia. Aurochs and human bones were uncovered from pits and burnt mounds at several Neolithic sites in England.
A cup found in the Greek site of Vaphio shows a hunting scene, in which people try to capture an aurochs. One of the bulls throws one hunter on the ground while attacking the second with its horns. The cup seems to date to Mycenaean Greece. Greeks and Paeonians hunted aurochs and used their huge horns as trophies, cups for wine, and offerings to the gods and heroes. The ox mentioned by Samus, Philippus of Thessalonica and Antipater as killed by Philip V of Macedon on the foothills of mountain Orvilos, was actually an aurochs; Philip offered the horns, which were long and the skin to a temple of Hercules.
The aurochs was described in Julius Caesar's Commentarii de Bello Gallico.
Aurochs were occasionally captured and exhibited in venatio shows in Roman amphitheatres such as the Colosseum. Aurochs horns were often used by Romans as hunting horns. | Aurochs | Wikipedia | 413 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
In the , Sigurd kills four aurochs. During the Middle Ages, aurochs horns were used as drinking horns including the horn of the last bull; many aurochs horn sheaths are preserved today. The aurochs drinking horn at Corpus Christi College, Cambridge was engraved with the college's coat of arms in the 17th century.
An aurochs head with a star between its horns and Christian iconographic elements represents the official coat of arms of Moldavia perpetuated for centuries.
Aurochs were hunted with arrows, nets and hunting dogs, and its hair on the forehead was cut from the living animal; belts were made out of this hair and believed to increase the fertility of women. When the aurochs was slaughtered, the os cordis was extracted from the heart; this bone contributed to the mystique and magical powers that were attributed to it.
In eastern Europe, the aurochs has left traces in expressions like "behaving like an aurochs" for a drunken person behaving badly, and "a bloke like an aurochs" for big and strong people. | Aurochs | Wikipedia | 231 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
Domestication
The earliest-known domestication of the aurochs dates to the Neolithic Revolution in the Fertile Crescent, where cattle hunted and kept by Neolithic farmers gradually decreased in size between 9800 and 7500 BC. Aurochs bones found at Mureybet and Göbekli Tepe are larger in size than cattle bones from later Neolithic settlements in northern Syria like Dja'de el-Mughara and Tell Halula.
In Late Neolithic sites of northern Iraq and western Iran dating to the sixth millennium BC, cattle remains are also smaller but more frequent, indicating that domesticated cattle were imported during the Halaf culture from the central Fertile Crescent region.
Results of genetic research indicate that the modern taurine cattle (Bos taurus) arose from 80 aurochs tamed in southeastern Anatolia and northern Syria about 10,500 years ago.
Taurine cattle spread into the Balkans and northern Italy along the Danube River and the coast of the Mediterranean Sea.
Hybridisation between male aurochs and early domestic cattle occurred in central Europe between 9500 and 1000 BC.
Analyses of mitochondrial DNA sequences of Italian aurochs specimens dated to 17–7,000 years ago and 51 modern cattle breeds revealed some degree of introgression of aurochs genes into south European cattle, indicating that female aurochs had contact with free-ranging domestic cattle. Cattle bones of various sizes found at a Chalcolithic settlement in the Kutná Hora District provide further evidence for hybridisation of aurochs and domestic cattle between 3000 and 2800 BC in the Bohemian region.
Whole genome sequencing of a 6,750-year-old aurochs bone found in England was compared with genome sequence data of 81 cattle and single-nucleotide polymorphism data of 1,225 cattle. Results revealed that British and Irish cattle breeds share some genetic variants with the aurochs specimen; early herders in Britain might have been responsible for the local gene flow from aurochs into the ancestors of British and Irish cattle. The Murboden cattle breed also exhibits sporadic introgression of female European aurochs into domestic cattle in the Alps. Domestic cattle continued to diminish in both body and horn size until the Middle Ages. | Aurochs | Wikipedia | 447 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
Comparative analysis of single-nucleotide polymorphisms and shared alleles revealed admixture between East Asian aurochs and introduced taurine cattle in ancient China, for example at Shimao. This suggested the incorporation of local aurochs into domestic cattle as far back as 4,000 years BP, either through spontaneous introgression, or the capture of different aurochs groups to supplement domestic stocks. The same study detected derived alleles shared by aurochs and modern taurine cattle in East Asia, especially among Tibetan breeds. Introgression with local aurochs could have facilitated rapid adaptation to new environments.
The Indian aurochs is thought to have been domesticated 10,000–8,000 years ago.
Aurochs fossils found at the Neolithic site of Mehrgarh in Pakistan are dated to around 8,000 years BP and represent some of the earliest evidence for its domestication on the Indian subcontinent. Female Indian aurochs contributed to the gene pool of zebu (Bos indicus) between 5,500 and 4,000 years BP during the expansion of pastoralism in northern India. The zebu initially spread eastwards to Southeast Asia.
Hybridisation between zebu and early taurine cattle occurred in the Near East after 4,000 years BP coinciding with the drought period during the 4.2-kiloyear event. The zebu was introduced to East Africa about 3,500–2,500 years ago, and reached Mongolia in the 13th and 14th centuries.
A third domestication event thought to have occurred in Egypt's Western Desert is not supported by results of an analysis of genetic admixture, introgression and migration patterns of 3,196 domestic cattle representing 180 populations. However, the same study supported extensive hybridization between taurine cattle in Africa, arrived from the Near East after domestication, and local wild African aurochs prior to the entry of the zebu in Africa. The zebu was introduced through Ancient Egypt and started to spread comprehensively through West Africa in the last 1,400 years, along with Arabic cultural influences. Most modern African cattle breeds are hybridized to a variable extent with Indicine cattle, with introgression being most reduced in areas of West Africa where the tse-tse fly is present.
Extinction | Aurochs | Wikipedia | 470 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
The Indian aurochs (B. p. namadicus) became extinct sometime during the Holocene period, likely due to habitat loss caused by expanding pastoralism and interbreeding with the domestic zebu. The timing of extinction of aurochs in the Indian subcontinent is unclear, due to difficulty distinguishing aurochs remains from those of domestic cattle, with a 2021 review suggesting remains from Mehrgarh, Pakistan, dating to around 8,000 years ago "might constitute the only dated and reliably identified evidence" of Holocene Indian aurochs. The extinction probably predates the historical period, due to a lack of references to the aurochs in Indian texts.
A 2014 review suggested that the youngest remains of African aurochs (B. p. mauritanicus) dated to around 6,000 years Before Present (BP), though some authors suggest that it may have survived until at least to the Roman period, as indicated by remains found in Buto and Faiyum in the Nile Delta.
In China, aurochs persisted until at least 3,600 BP.
The Eurasian aurochs (B. p. primigenius) was present in southern Sweden during the Holocene climatic optimum until at least 7,800 years BP. In Denmark, the first-known local extinction of the aurochs occurred after the sea level rise on the newly formed Danish islands about 8,000–7,500 years BP, and the last documented aurochs lived in southern Jutland around 3,000 years BP. The latest-known aurochs fossil in Great Britain dates to 3,245 years BP, and it was probably extinct by 3,000 years ago.
Excessive hunting began and continued until the aurochs was nearly extinct. The gradual extinction of the aurochs in Central Europe was concurrent with the clearcutting of large forest tracts between the 9th and 12th centuries.
By the 13th century, the aurochs existed only in small numbers in Eastern Europe, and hunting it became a privilege of nobles and later royals. The population in Hungary was declining from at least the 9th century and was extinct in the 13th century.
Findings from subfossil records indicate that wild aurochs might have survived in northwestern Transylvania until the 14th to 16th century, in western Moldavia until probably the early 17th century. | Aurochs | Wikipedia | 479 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
The last-known aurochs herd lived in a marshy woodland in Poland's Jaktorów Forest. It decreased from around 50 individuals in the mid 16th century to four individuals by 1601. The last aurochs cow died in 1627 from natural causes.
A 2021 study argued that the aurochs possibly survived in northeastern Bulgaria until at least the 17th century. A horn-core excavated in 2020 in Sofia was identified as being from an aurochs; the archaeological layer in which it was found was dated to the second half of the 17th or first half of the 18th century, suggesting that aurochs may have survived in Bulgaria until that date.
Breeding of aurochs-like cattle
In the early 1920s, Heinz Heck initiated a selective breeding program in Hellabrunn Zoo attempting to breed back the aurochs using several cattle breeds; the result is called Heck cattle.
Herds of these cattle were released to Oostvaardersplassen, a polder in the Netherlands in the 1980s as aurochs surrogates for naturalistic grazing with the aim to restore prehistorical landscapes. Large numbers of them died of starvation during the cold winters of 2005 and 2010, and the project of no interference ended in 2018.
Starting in 1996, Heck cattle were crossed with southern European cattle breeds such as Sayaguesa Cattle, Chianina and to a lesser extent Spanish Fighting Bulls in the hope of creating a more aurochs-like animal. The resulting crossbreeds are called Taurus cattle. Other breeding-back projects are the Tauros Programme and the Uruz Project.
However, approaches aiming at breeding an aurochs-like phenotype do not equate to an aurochs-like genotype. | Aurochs | Wikipedia | 356 | 2494 | https://en.wikipedia.org/wiki/Aurochs | Biology and health sciences | Artiodactyla | null |
In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the exit end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facilitate the expulsion of wastes that remain after digestion.
Bowel contents that pass through the anus include the gaseous flatus and the semi-solid feces, which (depending on the type of animal) include: indigestible matter such as bones, hair pellets, endozoochorous seeds and digestive rocks; residual food material after the digestible nutrients have been extracted, for example cellulose or lignin; ingested matter which would be toxic if it remained in the digestive tract; excreted metabolites like bilirubin-containing bile; and dead mucosal epithelia or excess gut bacteria and other endosymbionts. Passage of feces through the anus is typically controlled by muscular sphincters, and failure to stop unwanted passages results in fecal incontinence.
Amphibians, reptiles and birds use a similar orifice (known as the cloaca) for excreting liquid and solid wastes, for copulation and egg-laying. Monotreme mammals also have a cloaca, which is thought to be a feature inherited from the earliest amniotes. Marsupials have a single orifice for excreting both solids and liquids and, in females, a separate vagina for reproduction. Female placental mammals have completely separate orifices for defecation, urination, and reproduction; males have one opening for defecation and another for both urination and reproduction, although the channels flowing to that orifice are almost completely separate.
The development of the anus was an important stage in the evolution of multicellular animals. It appears to have happened at least twice, following different paths in protostomes and deuterostomes. This accompanied or facilitated other important evolutionary developments: the bilaterian body plan, the coelom, and metamerism, in which the body was built of repeated "modules" which could later specialize, such as the heads of most arthropods, which are composed of fused, specialized segments. | Anus | Wikipedia | 488 | 2500 | https://en.wikipedia.org/wiki/Anus | Biology and health sciences | Gastrointestinal tract | Biology |
In comb jellies, there are species with one and sometimes two permanent anuses, species like the warty comb jelly grows an anus, which then disappear when it is no longer needed.
Development
In animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the growth of the gut. In deuterostomes, the original dent becomes the anus while the gut eventually tunnels through to make another opening, which forms the mouth. The protostomes were so named because it was thought that in their embryos the dent formed the mouth first (proto– meaning "first") and the anus was formed later at the opening made by the other end of the gut. Research from 2001 shows the edges of the dent close up in the middles of protosomes, leaving openings at the ends which become the mouths and anuses. | Anus | Wikipedia | 198 | 2500 | https://en.wikipedia.org/wiki/Anus | Biology and health sciences | Gastrointestinal tract | Biology |
Amphetamine (contracted from alpha-methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, and obesity; it is also used to treat binge eating disorder in the form of its inactive prodrug lisdexamfetamine. Amphetamine was discovered as a chemical in 1887 by Lazăr Edeleanu, and then as a drug in the late 1920s. It exists as two enantiomers: levoamphetamine and dextroamphetamine. Amphetamine properly refers to a specific chemical, the racemic free base, which is equal parts of the two enantiomers in their pure amine forms. The term is frequently used informally to refer to any combination of the enantiomers, or to either of them alone. Historically, it has been used to treat nasal congestion and depression. Amphetamine is also used as an athletic performance enhancer and cognitive enhancer, and recreationally as an aphrodisiac and euphoriant. It is a prescription drug in many countries, and unauthorized possession and distribution of amphetamine are often tightly controlled due to the significant health risks associated with recreational use.
The first amphetamine pharmaceutical was Benzedrine, a brand which was used to treat a variety of conditions. Pharmaceutical amphetamine is prescribed as racemic amphetamine, Adderall, dextroamphetamine, or the inactive prodrug lisdexamfetamine. Amphetamine increases monoamine and excitatory neurotransmission in the brain, with its most pronounced effects targeting the norepinephrine and dopamine neurotransmitter systems. | Amphetamine | Wikipedia | 370 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
At therapeutic doses, amphetamine causes emotional and cognitive effects such as euphoria, change in desire for sex, increased wakefulness, and improved cognitive control. It induces physical effects such as improved reaction time, fatigue resistance, decreased appetite, elevated heart rate, and increased muscle strength. Larger doses of amphetamine may impair cognitive function and induce rapid muscle breakdown. Addiction is a serious risk with heavy recreational amphetamine use, but is unlikely to occur from long-term medical use at therapeutic doses. Very high doses can result in psychosis (e.g., hallucinations, delusions and paranoia) which rarely occurs at therapeutic doses even during long-term use. Recreational doses are generally much larger than prescribed therapeutic doses and carry a far greater risk of serious side effects.
Amphetamine belongs to the phenethylamine class. It is also the parent compound of its own structural class, the substituted amphetamines, which includes prominent substances such as bupropion, cathinone, MDMA, and methamphetamine. As a member of the phenethylamine class, amphetamine is also chemically related to the naturally occurring trace amine neuromodulators, specifically phenethylamine and , both of which are produced within the human body. Phenethylamine is the parent compound of amphetamine, while is a positional isomer of amphetamine that differs only in the placement of the methyl group.
Uses
Medical
Amphetamine is used to treat attention deficit hyperactivity disorder (ADHD), narcolepsy, obesity, and, in the form of lisdexamfetamine, binge eating disorder. It is sometimes prescribed for its past medical indications, particularly for depression and chronic pain.
ADHD
Long-term amphetamine exposure at sufficiently high doses in some animal species is known to produce abnormal dopamine system development or nerve damage, but, in humans with ADHD, long-term use of pharmaceutical amphetamines at therapeutic doses appears to improve brain development and nerve growth. Reviews of magnetic resonance imaging (MRI) studies suggest that long-term treatment with amphetamine decreases abnormalities in brain structure and function found in subjects with ADHD, and improves function in several parts of the brain, such as the right caudate nucleus of the basal ganglia. | Amphetamine | Wikipedia | 487 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Reviews of clinical stimulant research have established the safety and effectiveness of long-term continuous amphetamine use for the treatment of ADHD. Randomized controlled trials of continuous stimulant therapy for the treatment of ADHD spanning 2 years have demonstrated treatment effectiveness and safety. Two reviews have indicated that long-term continuous stimulant therapy for ADHD is effective for reducing the core symptoms of ADHD (i.e., hyperactivity, inattention, and impulsivity), enhancing quality of life and academic achievement, and producing improvements in a large number of functional outcomes across 9 categories of outcomes related to academics, antisocial behavior, driving, non-medicinal drug use, obesity, occupation, self-esteem, service use (i.e., academic, occupational, health, financial, and legal services), and social function. Additionally, a 2024 meta-analytic systematic review reported moderate improvements in quality of life when amphetamine treatment is used for ADHD. One review highlighted a nine-month randomized controlled trial of amphetamine treatment for ADHD in children that found an average increase of 4.5 IQ points, continued increases in attention, and continued decreases in disruptive behaviors and hyperactivity. Another review indicated that, based upon the longest follow-up studies conducted to date, lifetime stimulant therapy that begins during childhood is continuously effective for controlling ADHD symptoms and reduces the risk of developing a substance use disorder as an adult. A 2025 meta-analytic systematic review of 113 randomized controlled trials demonstrated that stimulant medications significantly improved core ADHD symptoms in adults over a three-month period, with good acceptability compared to other pharmacological and non-pharmacological treatments. | Amphetamine | Wikipedia | 360 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Models of ADHD suggest that it is associated with functional impairments in some of the brain's neurotransmitter systems; these functional impairments involve impaired dopamine neurotransmission in the mesocorticolimbic projection and norepinephrine neurotransmission in the noradrenergic projections from the locus coeruleus to the prefrontal cortex. Stimulants like methylphenidate and amphetamine are effective in treating ADHD because they increase neurotransmitter activity in these systems. Approximately 80% of those who use these stimulants see improvements in ADHD symptoms. Children with ADHD who use stimulant medications generally have better relationships with peers and family members, perform better in school, are less distractible and impulsive, and have longer attention spans. The Cochrane reviews on the treatment of ADHD in children, adolescents, and adults with pharmaceutical amphetamines stated that short-term studies have demonstrated that these drugs decrease the severity of symptoms, but they have higher discontinuation rates than non-stimulant medications due to their adverse side effects. A Cochrane review on the treatment of ADHD in children with tic disorders such as Tourette syndrome indicated that stimulants in general do not make tics worse, but high doses of dextroamphetamine could exacerbate tics in some individuals.
Binge eating disorder
Binge eating disorder (BED) is characterized by recurrent and persistent episodes of compulsive binge eating. These episodes are often accompanied by marked distress and a feeling of loss of control over eating. The pathophysiology of BED is not fully understood, but it is believed to involve dysfunctional dopaminergic reward circuitry along the cortico-striatal-thalamic-cortical loop. As of July 2024, lisdexamfetamine is the only USFDA- and TGA-approved pharmacotherapy for BED. Evidence suggests that lisdexamfetamine's treatment efficacy in BED is underpinned at least in part by a psychopathological overlap between BED and ADHD, with the latter conceptualized as a cognitive control disorder that also benefits from treatment with lisdexamfetamine. | Amphetamine | Wikipedia | 480 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Lisdexamfetamine's therapeutic effects for BED primarily involve direct action in the central nervous system after conversion to its pharmacologically active metabolite, dextroamphetamine. Centrally, dextroamphetamine increases neurotransmitter activity of dopamine and norepinephrine in prefrontal cortical regions that regulate cognitive control of behavior. Similar to its therapeutic effect in ADHD, dextroamphetamine enhances cognitive control and may reduce impulsivity in patients with BED by enhancing the cognitive processes responsible for overriding prepotent feeding responses that precede binge eating episodes. In addition, dextroamphetamine's actions outside of the central nervous system may also contribute to its treatment effects in BED. Peripherally, dextroamphetamine triggers lipolysis through noradrenergic signaling in adipose fat cells, leading to the release of triglycerides into blood plasma to be utilized as a fuel substrate. Dextroamphetamine also activates TAAR1 in peripheral organs along the gastrointestinal tract that are involved in the regulation of food intake and body weight. Together, these actions confer an anorexigenic effect that promotes satiety in response to feeding and may decrease binge eating as a secondary effect. | Amphetamine | Wikipedia | 269 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Medical reviews of randomized controlled trials have demonstrated that lisdexamfetamine, at doses between 50–70 mg, is safe and effective for the treatment of moderate-to-severe BED in adults. These reviews suggest that lisdexamfetamine is persistently effective at treating BED and is associated with significant reductions in the number of binge eating days and binge eating episodes per week. Furthermore, a meta-analytic systematic review highlighted an open-label, 12-month extension safety and tolerability study that reported lisdexamfetamine remained effective at reducing the number of binge eating days for the duration of the study. In addition, both a review and a meta-analytic systematic review found lisdexamfetamine to be superior to placebo in several secondary outcome measures, including persistent binge eating cessation, reduction of obsessive-compulsive related binge eating symptoms, reduction of body-weight, and reduction of triglycerides. Lisdexamfetamine, like all pharmaceutical amphetamines, has direct appetite suppressant effects that may be therapeutically useful in both BED and its comorbidities. Based on reviews of neuroimaging studies involving BED-diagnosed participants, therapeautic neuroplasticity in dopaminergic and noradrenergic pathways from long-term use of lisdexamfetamine may be implicated in lasting improvements in the regulation of eating behaviors that are observed even after the drug is discontinued.
Narcolepsy
Narcolepsy is a chronic sleep-wake disorder that is associated with excessive daytime sleepiness, cataplexy, and sleep paralysis. Patients with narcolepsy are diagnosed as either type 1 or type 2, with only the former presenting cataplexy symptoms. Type 1 narcolepsy results from the loss of approximately 70,000 orexin-releasing neurons in the lateral hypothalamus, leading to significantly reduced cerebrospinal orexin levels; this reduction is a diagnostic biomarker for type 1 narcolepsy. Lateral hypothalamic orexin neurons innervate every component of the ascending reticular activating system (ARAS), which includes noradrenergic, dopaminergic, histaminergic, and serotonergic nuclei that promote wakefulness. | Amphetamine | Wikipedia | 490 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Amphetamine’s therapeutic mode of action in narcolepsy primarily involves increasing monoamine neurotransmitter activity in the ARAS. This includes noradrenergic neurons in the locus coeruleus, dopaminergic neurons in the ventral tegmental area, histaminergic neurons in the tuberomammillary nucleus, and serotonergic neurons in the dorsal raphe nucleus. Dextroamphetamine, the more dopaminergic enantiomer of amphetamine, is particularly effective at promoting wakefulness because dopamine release has the greatest influence on cortical activation and cognitive arousal, relative to other monoamines. In contrast, levoamphetamine may have a greater effect on cataplexy, a symptom more sensitive to the effects of norepinephrine and serotonin. Noradrenergic and serotonergic nuclei in the ARAS are involved in the regulation of the REM sleep cycle and function as "REM-off" cells, with amphetamine's effect on norepinephrine and serotonin contributing to the suppression of REM sleep and a possible reduction of cataplexy at high doses.
The American Academy of Sleep Medicine (AASM) 2021 clinical practice guideline conditionally recommends dextroamphetamine for the treatment of both type 1 and type 2 narcolepsy. Treatment with pharmaceutical amphetamines is generally less preferred relative to other stimulants (e.g., modafinil) and is considered a third-line treatment option. Medical reviews indicate that amphetamine is safe and effective for the treatment of narcolepsy. Amphetamine appears to be most effective at improving symptoms associated with hypersomnolence, with three reviews finding clinically significant reductions in daytime sleepiness in patients with narcolepsy. Additionally, these reviews suggest that amphetamine may dose-dependently improve cataplexy symptoms. However, the quality of evidence for these findings is low and is consequently reflected in the AASM's conditional recommendation for dextroamphetamine as a treatment option for narcolepsy.
Enhancing performance | Amphetamine | Wikipedia | 451 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Cognitive performance
In 2015, a systematic review and a meta-analysis of high quality clinical trials found that, when used at low (therapeutic) doses, amphetamine produces modest yet unambiguous improvements in cognition, including working memory, long-term episodic memory, inhibitory control, and some aspects of attention, in normal healthy adults; these cognition-enhancing effects of amphetamine are known to be partially mediated through the indirect activation of both dopamine D1 receptor and α2-adrenergic receptor in the prefrontal cortex. A systematic review from 2014 found that low doses of amphetamine also improve memory consolidation, in turn leading to improved recall of information. Therapeutic doses of amphetamine also enhance cortical network efficiency, an effect which mediates improvements in working memory in all individuals. Amphetamine and other ADHD stimulants also improve task saliency (motivation to perform a task) and increase arousal (wakefulness), in turn promoting goal-directed behavior. Stimulants such as amphetamine can improve performance on difficult and boring tasks and are used by some students as a study and test-taking aid. Based upon studies of self-reported illicit stimulant use, of college students use diverted ADHD stimulants, which are primarily used for enhancement of academic performance rather than as recreational drugs. However, high amphetamine doses that are above the therapeutic range can interfere with working memory and other aspects of cognitive control.
Physical performance | Amphetamine | Wikipedia | 308 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Amphetamine is used by some athletes for its psychological and athletic performance-enhancing effects, such as increased endurance and alertness; however, non-medical amphetamine use is prohibited at sporting events that are regulated by collegiate, national, and international anti-doping agencies. In healthy people at oral therapeutic doses, amphetamine has been shown to increase muscle strength, acceleration, athletic performance in anaerobic conditions, and endurance (i.e., it delays the onset of fatigue), while improving reaction time. Amphetamine improves endurance and reaction time primarily through reuptake inhibition and release of dopamine in the central nervous system. Amphetamine and other dopaminergic drugs also increase power output at fixed levels of perceived exertion by overriding a "safety switch", allowing the core temperature limit to increase in order to access a reserve capacity that is normally off-limits. At therapeutic doses, the adverse effects of amphetamine do not impede athletic performance; however, at much higher doses, amphetamine can induce effects that severely impair performance, such as rapid muscle breakdown and elevated body temperature. | Amphetamine | Wikipedia | 231 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Recreational
Amphetamine, specifically the more dopaminergic dextrorotatory enantiomer (dextroamphetamine), is also used recreationally as a euphoriant and aphrodisiac, and like other amphetamines; is used as a club drug for its energetic and euphoric high. Dextroamphetamine (d-amphetamine) is considered to have a high potential for misuse in a recreational manner since individuals typically report feeling euphoric, more alert, and more energetic after taking the drug. A notable part of the 1960s mod subculture in the UK was recreational amphetamine use, which was used to fuel all-night dances at clubs like Manchester's Twisted Wheel. Newspaper reports described dancers emerging from clubs at 5 a.m. with dilated pupils. Mods used the drug for stimulation and alertness, which they viewed as different from the intoxication caused by alcohol and other drugs. Dr. Andrew Wilson argues that for a significant minority, "amphetamines symbolised the smart, on-the-ball, cool image" and that they sought "stimulation not intoxication [...] greater awareness, not escape" and "confidence and articulacy" rather than the "drunken rowdiness of previous generations." Dextroamphetamine's dopaminergic (rewarding) properties affect the mesocorticolimbic circuit; a group of neural structures responsible for incentive salience (i.e., "wanting"; desire or craving for a reward and motivation), positive reinforcement and positively-valenced emotions, particularly ones involving pleasure. Large recreational doses of dextroamphetamine may produce symptoms of dextroamphetamine overdose. Recreational users sometimes open dexedrine capsules and crush the contents in order to insufflate (snort) it or subsequently dissolve it in water and inject it. Immediate-release formulations have higher potential for abuse via insufflation (snorting) or intravenous injection due to a more favorable pharmacokinetic profile and easy crushability (especially tablets). Injection into the bloodstream can be dangerous because insoluble fillers within the tablets can block small blood vessels. Chronic overuse of dextroamphetamine can lead to severe drug dependence, resulting in withdrawal symptoms when drug use stops.
Contraindications | Amphetamine | Wikipedia | 497 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
According to the International Programme on Chemical Safety (IPCS) and the U.S. Food and Drug Administration (FDA), amphetamine is contraindicated in people with a history of drug abuse, cardiovascular disease, severe agitation, or severe anxiety. It is also contraindicated in individuals with advanced arteriosclerosis (hardening of the arteries), glaucoma (increased eye pressure), hyperthyroidism (excessive production of thyroid hormone), or moderate to severe hypertension. These agencies indicate that people who have experienced allergic reactions to other stimulants or who are taking monoamine oxidase inhibitors (MAOIs) should not take amphetamine, although safe concurrent use of amphetamine and monoamine oxidase inhibitors has been documented. These agencies also state that anyone with anorexia nervosa, bipolar disorder, depression, hypertension, liver or kidney problems, mania, psychosis, Raynaud's phenomenon, seizures, thyroid problems, tics, or Tourette syndrome should monitor their symptoms while taking amphetamine. Evidence from human studies indicates that therapeutic amphetamine use does not cause developmental abnormalities in the fetus or newborns (i.e., it is not a human teratogen), but amphetamine abuse does pose risks to the fetus. Amphetamine has also been shown to pass into breast milk, so the IPCS and the FDA advise mothers to avoid breastfeeding when using it. Due to the potential for reversible growth impairments, the FDA advises monitoring the height and weight of children and adolescents prescribed an amphetamine pharmaceutical.
Adverse effects
The adverse side effects of amphetamine are many and varied, and the amount of amphetamine used is the primary factor in determining the likelihood and severity of adverse effects. Amphetamine products such as Adderall, Dexedrine, and their generic equivalents are currently approved by the U.S. FDA for long-term therapeutic use. Recreational use of amphetamine generally involves much larger doses, which have a greater risk of serious adverse drug effects than dosages used for therapeutic purposes. | Amphetamine | Wikipedia | 438 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Physical
Cardiovascular side effects can include hypertension or hypotension from a vasovagal response, Raynaud's phenomenon (reduced blood flow to the hands and feet), and tachycardia (increased heart rate). Sexual side effects in males may include erectile dysfunction, frequent erections, or prolonged erections. Gastrointestinal side effects may include abdominal pain, constipation, diarrhea, and nausea. Other potential physical side effects include appetite loss, blurred vision, dry mouth, excessive grinding of the teeth, nosebleed, profuse sweating, rhinitis medicamentosa (drug-induced nasal congestion), reduced seizure threshold, tics (a type of movement disorder), and weight loss. Dangerous physical side effects are rare at typical pharmaceutical doses.
Amphetamine stimulates the medullary respiratory centers, producing faster and deeper breaths. In a normal person at therapeutic doses, this effect is usually not noticeable, but when respiration is already compromised, it may be evident. Amphetamine also induces contraction in the urinary bladder sphincter, the muscle which controls urination, which can result in difficulty urinating. This effect can be useful in treating bed wetting and loss of bladder control. The effects of amphetamine on the gastrointestinal tract are unpredictable. If intestinal activity is high, amphetamine may reduce gastrointestinal motility (the rate at which content moves through the digestive system); however, amphetamine may increase motility when the smooth muscle of the tract is relaxed. Amphetamine also has a slight analgesic effect and can enhance the pain relieving effects of opioids.
FDA-commissioned studies from 2011 indicate that in children, young adults, and adults there is no association between serious adverse cardiovascular events (sudden death, heart attack, and stroke) and the medical use of amphetamine or other ADHD stimulants. However, amphetamine pharmaceuticals are contraindicated in individuals with cardiovascular disease. | Amphetamine | Wikipedia | 419 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Psychological
At normal therapeutic doses, the most common psychological side effects of amphetamine include increased alertness, apprehension, concentration, initiative, self-confidence and sociability, mood swings (elated mood followed by mildly depressed mood), insomnia or wakefulness, and decreased sense of fatigue. Less common side effects include anxiety, change in libido, grandiosity, irritability, repetitive or obsessive behaviors, and restlessness; these effects depend on the user's personality and current mental state. Amphetamine psychosis (e.g., delusions and paranoia) can occur in heavy users. Although very rare, this psychosis can also occur at therapeutic doses during long-term therapy. According to the FDA, "there is no systematic evidence" that stimulants produce aggressive behavior or hostility.
Amphetamine has also been shown to produce a conditioned place preference in humans taking therapeutic doses, meaning that individuals acquire a preference for spending time in places where they have previously used amphetamine.
Reinforcement disorders
Addiction
Addiction is a serious risk with heavy recreational amphetamine use, but is unlikely to occur from long-term medical use at therapeutic doses; in fact, lifetime stimulant therapy for ADHD that begins during childhood reduces the risk of developing substance use disorders as an adult. Pathological overactivation of the mesolimbic pathway, a dopamine pathway that connects the ventral tegmental area to the nucleus accumbens, plays a central role in amphetamine addiction. Individuals who frequently self-administer high doses of amphetamine have a high risk of developing an amphetamine addiction, since chronic use at high doses gradually increases the level of accumbal ΔFosB, a "molecular switch" and "master control protein" for addiction. Once nucleus accumbens ΔFosB is sufficiently overexpressed, it begins to increase the severity of addictive behavior (i.e., compulsive drug-seeking) with further increases in its expression. While there are currently no effective drugs for treating amphetamine addiction, regularly engaging in sustained aerobic exercise appears to reduce the risk of developing such an addiction. Exercise therapy improves clinical treatment outcomes and may be used as an adjunct therapy with behavioral therapies for addiction. | Amphetamine | Wikipedia | 467 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Biomolecular mechanisms
Chronic use of amphetamine at excessive doses causes alterations in gene expression in the mesocorticolimbic projection, which arise through transcriptional and epigenetic mechanisms. The most important transcription factors that produce these alterations are Delta FBJ murine osteosarcoma viral oncogene homolog B (ΔFosB), cAMP response element binding protein (CREB), and nuclear factor-kappa B (NF-κB). ΔFosB is the most significant biomolecular mechanism in addiction because ΔFosB overexpression (i.e., an abnormally high level of gene expression which produces a pronounced gene-related phenotype) in the D1-type medium spiny neurons in the nucleus accumbens is necessary and sufficient for many of the neural adaptations and regulates multiple behavioral effects (e.g., reward sensitization and escalating drug self-administration) involved in addiction. Once ΔFosB is sufficiently overexpressed, it induces an addictive state that becomes increasingly more severe with further increases in ΔFosB expression. It has been implicated in addictions to alcohol, cannabinoids, cocaine, methylphenidate, nicotine, opioids, phencyclidine, propofol, and substituted amphetamines, among others. | Amphetamine | Wikipedia | 281 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
ΔJunD, a transcription factor, and G9a, a histone methyltransferase enzyme, both oppose the function of ΔFosB and inhibit increases in its expression. Sufficiently overexpressing ΔJunD in the nucleus accumbens with viral vectors can completely block many of the neural and behavioral alterations seen in chronic drug abuse (i.e., the alterations mediated by ΔFosB). Similarly, accumbal G9a hyperexpression results in markedly increased histone 3 lysine residue 9 dimethylation (H3K9me2) and blocks the induction of ΔFosB-mediated neural and behavioral plasticity by chronic drug use, which occurs via H3K9me2-mediated repression of transcription factors for ΔFosB and H3K9me2-mediated repression of various ΔFosB transcriptional targets (e.g., CDK5). ΔFosB also plays an important role in regulating behavioral responses to natural rewards, such as palatable food, sex, and exercise. Since both natural rewards and addictive drugs induce the expression of ΔFosB (i.e., they cause the brain to produce more of it), chronic acquisition of these rewards can result in a similar pathological state of addiction. Consequently, ΔFosB is the most significant factor involved in both amphetamine addiction and amphetamine-induced sexual addictions, which are compulsive sexual behaviors that result from excessive sexual activity and amphetamine use. These sexual addictions are associated with a dopamine dysregulation syndrome which occurs in some patients taking dopaminergic drugs.
The effects of amphetamine on gene regulation are both dose- and route-dependent. Most of the research on gene regulation and addiction is based upon animal studies with intravenous amphetamine administration at very high doses. The few studies that have used equivalent (weight-adjusted) human therapeutic doses and oral administration show that these changes, if they occur, are relatively minor. This suggests that medical use of amphetamine does not significantly affect gene regulation.
Pharmacological treatments | Amphetamine | Wikipedia | 436 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
there is no effective pharmacotherapy for amphetamine addiction. Reviews from 2015 and 2016 indicated that TAAR1-selective agonists have significant therapeutic potential as a treatment for psychostimulant addictions; however, the only compounds which are known to function as TAAR1-selective agonists are experimental drugs. Amphetamine addiction is largely mediated through increased activation of dopamine receptors and NMDA receptors in the nucleus accumbens; magnesium ions inhibit NMDA receptors by blocking the receptor calcium channel. One review suggested that, based upon animal testing, pathological (addiction-inducing) psychostimulant use significantly reduces the level of intracellular magnesium throughout the brain. Supplemental magnesium treatment has been shown to reduce amphetamine self-administration (i.e., doses given to oneself) in humans, but it is not an effective monotherapy for amphetamine addiction.
A systematic review and meta-analysis from 2019 assessed the efficacy of 17 different pharmacotherapies used in randomized controlled trials (RCTs) for amphetamine and methamphetamine addiction; it found only low-strength evidence that methylphenidate might reduce amphetamine or methamphetamine self-administration. There was low- to moderate-strength evidence of no benefit for most of the other medications used in RCTs, which included antidepressants (bupropion, mirtazapine, sertraline), antipsychotics (aripiprazole), anticonvulsants (topiramate, baclofen, gabapentin), naltrexone, varenicline, citicoline, ondansetron, prometa, riluzole, atomoxetine, dextroamphetamine, and modafinil. | Amphetamine | Wikipedia | 378 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Behavioral treatments
A 2018 systematic review and network meta-analysis of 50 trials involving 12 different psychosocial interventions for amphetamine, methamphetamine, or cocaine addiction found that combination therapy with both contingency management and community reinforcement approach had the highest efficacy (i.e., abstinence rate) and acceptability (i.e., lowest dropout rate). Other treatment modalities examined in the analysis included monotherapy with contingency management or community reinforcement approach, cognitive behavioral therapy, 12-step programs, non-contingent reward-based therapies, psychodynamic therapy, and other combination therapies involving these.
Additionally, research on the neurobiological effects of physical exercise suggests that daily aerobic exercise, especially endurance exercise (e.g., marathon running), prevents the development of drug addiction and is an effective adjunct therapy (i.e., a supplemental treatment) for amphetamine addiction. Exercise leads to better treatment outcomes when used as an adjunct treatment, particularly for psychostimulant addictions. In particular, aerobic exercise decreases psychostimulant self-administration, reduces the reinstatement (i.e., relapse) of drug-seeking, and induces increased dopamine receptor D2 (DRD2) density in the striatum. This is the opposite of pathological stimulant use, which induces decreased striatal DRD2 density. One review noted that exercise may also prevent the development of a drug addiction by altering ΔFosB or immunoreactivity in the striatum or other parts of the reward system. | Amphetamine | Wikipedia | 340 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Dependence and withdrawal
Drug tolerance develops rapidly in amphetamine abuse (i.e., recreational amphetamine use), so periods of extended abuse require increasingly larger doses of the drug in order to achieve the same effect.
According to a Cochrane review on withdrawal in individuals who compulsively use amphetamine and methamphetamine, "when chronic heavy users abruptly discontinue amphetamine use, many report a time-limited withdrawal syndrome that occurs within 24 hours of their last dose." This review noted that withdrawal symptoms in chronic, high-dose users are frequent, occurring in roughly 88% of cases, and persist for weeks with a marked "crash" phase occurring during the first week. Amphetamine withdrawal symptoms can include anxiety, drug craving, depressed mood, fatigue, increased appetite, increased movement or decreased movement, lack of motivation, sleeplessness or sleepiness, and lucid dreams. The review indicated that the severity of withdrawal symptoms is positively correlated with the age of the individual and the extent of their dependence. Mild withdrawal symptoms from the discontinuation of amphetamine treatment at therapeutic doses can be avoided by tapering the dose.
Overdose
An amphetamine overdose can lead to many different symptoms, but is rarely fatal with appropriate care. The severity of overdose symptoms increases with dosage and decreases with drug tolerance to amphetamine. Tolerant individuals have been known to take as much as 5 grams of amphetamine in a day, which is roughly 100 times the maximum daily therapeutic dose. Symptoms of a moderate and extremely large overdose are listed below; fatal amphetamine poisoning usually also involves convulsions and coma. In 2013, overdose on amphetamine, methamphetamine, and other compounds implicated in an "amphetamine use disorder" resulted in an estimated 3,788 deaths worldwide ( deaths, 95% confidence). | Amphetamine | Wikipedia | 381 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Toxicity
In rodents and primates, sufficiently high doses of amphetamine cause dopaminergic neurotoxicity, or damage to dopamine neurons, which is characterized by dopamine terminal degeneration and reduced transporter and receptor function. There is no evidence that amphetamine is directly neurotoxic in humans. However, large doses of amphetamine may indirectly cause dopaminergic neurotoxicity as a result of hyperpyrexia, the excessive formation of reactive oxygen species, and increased autoxidation of dopamine. Animal models of neurotoxicity from high-dose amphetamine exposure indicate that the occurrence of hyperpyrexia (i.e., core body temperature ≥ 40 °C) is necessary for the development of amphetamine-induced neurotoxicity. Prolonged elevations of brain temperature above 40 °C likely promote the development of amphetamine-induced neurotoxicity in laboratory animals by facilitating the production of reactive oxygen species, disrupting cellular protein function, and transiently increasing blood–brain barrier permeability.
Psychosis
An amphetamine overdose can result in a stimulant psychosis that may involve a variety of symptoms, such as delusions and paranoia. A Cochrane review on treatment for amphetamine, dextroamphetamine, and methamphetamine psychosis states that about of users fail to recover completely. According to the same review, there is at least one trial that shows antipsychotic medications effectively resolve the symptoms of acute amphetamine psychosis. Psychosis rarely arises from therapeutic use.
Drug interactions | Amphetamine | Wikipedia | 334 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Many types of substances are known to interact with amphetamine, resulting in altered drug action or metabolism of amphetamine, the interacting substance, or both. Inhibitors of enzymes that metabolize amphetamine (e.g., CYP2D6 and FMO3) will prolong its elimination half-life, meaning that its effects will last longer. Amphetamine also interacts with , particularly monoamine oxidase A inhibitors, since both MAOIs and amphetamine increase plasma catecholamines (i.e., norepinephrine and dopamine); therefore, concurrent use of both is dangerous. Amphetamine modulates the activity of most psychoactive drugs. In particular, amphetamine may decrease the effects of sedatives and depressants and increase the effects of stimulants and antidepressants. Amphetamine may also decrease the effects of antihypertensives and antipsychotics due to its effects on blood pressure and dopamine respectively. Zinc supplementation may reduce the minimum effective dose of amphetamine when it is used for the treatment of ADHD. Norepinephrine reuptake inhibitors (NRIs) like atomoxetine prevent norepinephrine release induced by amphetamines and have been found to reduce the stimulant, euphoriant, and sympathomimetic effects of dextroamphetamine in humans.
In general, there is no significant interaction when consuming amphetamine with food, but the pH of gastrointestinal content and urine affects the absorption and excretion of amphetamine, respectively. Acidic substances reduce the absorption of amphetamine and increase urinary excretion, and alkaline substances do the opposite. Due to the effect pH has on absorption, amphetamine also interacts with gastric acid reducers such as proton pump inhibitors and H2 antihistamines, which increase gastrointestinal pH (i.e., make it less acidic).
Pharmacology
Pharmacodynamics | Amphetamine | Wikipedia | 432 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Amphetamine exerts its behavioral effects by altering the use of monoamines as neuronal signals in the brain, primarily in catecholamine neurons in the reward and executive function pathways of the brain. The concentrations of the main neurotransmitters involved in reward circuitry and executive functioning, dopamine and norepinephrine, increase dramatically in a dose-dependent manner by amphetamine because of its effects on monoamine transporters. The reinforcing and motivational salience-promoting effects of amphetamine are due mostly to enhanced dopaminergic activity in the mesolimbic pathway. The euphoric and locomotor-stimulating effects of amphetamine are dependent upon the magnitude and speed by which it increases synaptic dopamine and norepinephrine concentrations in the striatum.
Amphetamine has been identified as a potent full agonist of trace amine-associated receptor 1 (TAAR1), a and G protein-coupled receptor (GPCR) discovered in 2001, which is important for regulation of brain monoamines. Activation of increases production via adenylyl cyclase activation and inhibits monoamine transporter function. Monoamine autoreceptors (e.g., D2 short, presynaptic α2, and presynaptic 5-HT1A) have the opposite effect of TAAR1, and together these receptors provide a regulatory system for monoamines. Notably, amphetamine and trace amines possess high binding affinities for TAAR1, but not for monoamine autoreceptors. Imaging studies indicate that monoamine reuptake inhibition by amphetamine and trace amines is site specific and depends upon the presence of TAAR1 in the associated monoamine neurons. | Amphetamine | Wikipedia | 375 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
In addition to the neuronal monoamine transporters, amphetamine also inhibits both vesicular monoamine transporters, VMAT1 and VMAT2, as well as SLC1A1, SLC22A3, and SLC22A5. SLC1A1 is excitatory amino acid transporter 3 (EAAT3), a glutamate transporter located in neurons, SLC22A3 is an extraneuronal monoamine transporter that is present in astrocytes, and SLC22A5 is a high-affinity carnitine transporter. Amphetamine is known to strongly induce cocaine- and amphetamine-regulated transcript (CART) gene expression, a neuropeptide involved in feeding behavior, stress, and reward, which induces observable increases in neuronal development and survival in vitro. The CART receptor has yet to be identified, but there is significant evidence that CART binds to a unique . Amphetamine also inhibits monoamine oxidases at very high doses, resulting in less monoamine and trace amine metabolism and consequently higher concentrations of synaptic monoamines. In humans, the only post-synaptic receptor at which amphetamine is known to bind is the receptor, where it acts as an agonist with low micromolar affinity.
The full profile of amphetamine's short-term drug effects in humans is mostly derived through increased cellular communication or neurotransmission of dopamine, serotonin, norepinephrine, epinephrine, histamine, CART peptides, endogenous opioids, adrenocorticotropic hormone, corticosteroids, and glutamate, which it affects through interactions with , , , , , , and possibly other biological targets. Amphetamine also activates seven human carbonic anhydrase enzymes, several of which are expressed in the human brain.
Dextroamphetamine is a more potent agonist of than levoamphetamine. Consequently, dextroamphetamine produces greater stimulation than levoamphetamine, roughly three to four times more, but levoamphetamine has slightly stronger cardiovascular and peripheral effects. | Amphetamine | Wikipedia | 464 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Dopamine
In certain brain regions, amphetamine increases the concentration of dopamine in the synaptic cleft. Amphetamine can enter the presynaptic neuron either through or by diffusing across the neuronal membrane directly. As a consequence of DAT uptake, amphetamine produces competitive reuptake inhibition at the transporter. Upon entering the presynaptic neuron, amphetamine activates which, through protein kinase A (PKA) and protein kinase C (PKC) signaling, causes DAT phosphorylation. Phosphorylation by either protein kinase can result in DAT internalization ( reuptake inhibition), but phosphorylation alone induces the reversal of dopamine transport through DAT (i.e., dopamine efflux). Amphetamine is also known to increase intracellular calcium, an effect which is associated with DAT phosphorylation through an unidentified Ca2+/calmodulin-dependent protein kinase (CAMK)-dependent pathway, in turn producing dopamine efflux. Through direct activation of G protein-coupled inwardly-rectifying potassium channels, reduces the firing rate of dopamine neurons, preventing a hyper-dopaminergic state.
Amphetamine is also a substrate for the presynaptic vesicular monoamine transporter, . Following amphetamine uptake at VMAT2, amphetamine induces the collapse of the vesicular pH gradient, which results in the release of dopamine molecules from synaptic vesicles into the cytosol via dopamine efflux through VMAT2. Subsequently, the cytosolic dopamine molecules are released from the presynaptic neuron into the synaptic cleft via reverse transport at .
Norepinephrine
Similar to dopamine, amphetamine dose-dependently increases the level of synaptic norepinephrine, the direct precursor of epinephrine. Based upon neuronal expression, amphetamine is thought to affect norepinephrine analogously to dopamine. In other words, amphetamine induces TAAR1-mediated efflux and reuptake inhibition at phosphorylated , competitive NET reuptake inhibition, and norepinephrine release from . | Amphetamine | Wikipedia | 491 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Serotonin
Amphetamine exerts analogous, yet less pronounced, effects on serotonin as on dopamine and norepinephrine. Amphetamine affects serotonin via and, like norepinephrine, is thought to phosphorylate via . Like dopamine, amphetamine has low, micromolar affinity at the human 5-HT1A receptor.
Other neurotransmitters, peptides, hormones, and enzymes
Acute amphetamine administration in humans increases endogenous opioid release in several brain structures in the reward system. Extracellular levels of glutamate, the primary excitatory neurotransmitter in the brain, have been shown to increase in the striatum following exposure to amphetamine. This increase in extracellular glutamate presumably occurs via the amphetamine-induced internalization of EAAT3, a glutamate reuptake transporter, in dopamine neurons. Amphetamine also induces the selective release of histamine from mast cells and efflux from histaminergic neurons through . Acute amphetamine administration can also increase adrenocorticotropic hormone and corticosteroid levels in blood plasma by stimulating the hypothalamic–pituitary–adrenal axis.
In December 2017, the first study assessing the interaction between amphetamine and human carbonic anhydrase enzymes was published; of the eleven carbonic anhydrase enzymes it examined, it found that amphetamine potently activates seven, four of which are highly expressed in the human brain, with low nanomolar through low micromolar activating effects. Based upon preclinical research, cerebral carbonic anhydrase activation has cognition-enhancing effects; but, based upon the clinical use of carbonic anhydrase inhibitors, carbonic anhydrase activation in other tissues may be associated with adverse effects, such as ocular activation exacerbating glaucoma. | Amphetamine | Wikipedia | 424 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Pharmacokinetics
The oral bioavailability of amphetamine varies with gastrointestinal pH; it is well absorbed from the gut, and bioavailability is typically 90%. Amphetamine is a weak base with a pKa of 9.9; consequently, when the pH is basic, more of the drug is in its lipid soluble free base form, and more is absorbed through the lipid-rich cell membranes of the gut epithelium. Conversely, an acidic pH means the drug is predominantly in a water-soluble cationic (salt) form, and less is absorbed. Approximately of amphetamine circulating in the bloodstream is bound to plasma proteins. Following absorption, amphetamine readily distributes into most tissues in the body, with high concentrations occurring in cerebrospinal fluid and brain tissue.
The half-lives of amphetamine enantiomers differ and vary with urine pH. At normal urine pH, the half-lives of dextroamphetamine and levoamphetamine are hours and hours, respectively. Highly acidic urine will reduce the enantiomer half-lives to 7 hours; highly alkaline urine will increase the half-lives up to 34 hours. The immediate-release and extended release variants of salts of both isomers reach peak plasma concentrations at 3 hours and 7 hours post-dose respectively. Amphetamine is eliminated via the kidneys, with of the drug being excreted unchanged at normal urinary pH. When the urinary pH is basic, amphetamine is in its free base form, so less is excreted. When urine pH is abnormal, the urinary recovery of amphetamine may range from a low of 1% to a high of 75%, depending mostly upon whether urine is too basic or acidic, respectively. Following oral administration, amphetamine appears in urine within 3 hours. Roughly 90% of ingested amphetamine is eliminated 3 days after the last oral dose. | Amphetamine | Wikipedia | 412 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
CYP2D6, dopamine β-hydroxylase (DBH), flavin-containing monooxygenase 3 (FMO3), butyrate-CoA ligase (XM-ligase), and glycine N-acyltransferase (GLYAT) are the enzymes known to metabolize amphetamine or its metabolites in humans. Amphetamine has a variety of excreted metabolic products, including , , , benzoic acid, hippuric acid, norephedrine, and phenylacetone. Among these metabolites, the active sympathomimetics are , , and norephedrine. The main metabolic pathways involve aromatic para-hydroxylation, aliphatic alpha- and beta-hydroxylation, N-oxidation, N-dealkylation, and deamination. The known metabolic pathways, detectable metabolites, and metabolizing enzymes in humans include the following:
Pharmacomicrobiomics
The human metagenome (i.e., the genetic composition of an individual and all microorganisms that reside on or within the individual's body) varies considerably between individuals. Since the total number of microbial and viral cells in the human body (over 100 trillion) greatly outnumbers human cells (tens of trillions), there is considerable potential for interactions between drugs and an individual's microbiome, including: drugs altering the composition of the human microbiome, drug metabolism by microbial enzymes modifying the drug's pharmacokinetic profile, and microbial drug metabolism affecting a drug's clinical efficacy and toxicity profile. The field that studies these interactions is known as pharmacomicrobiomics.
Similar to most biomolecules and other orally administered xenobiotics (i.e., drugs), amphetamine is predicted to undergo promiscuous metabolism by human gastrointestinal microbiota (primarily bacteria) prior to absorption into the blood stream. The first amphetamine-metabolizing microbial enzyme, tyramine oxidase from a strain of E. coli commonly found in the human gut, was identified in 2019. This enzyme was found to metabolize amphetamine, tyramine, and phenethylamine with roughly the same binding affinity for all three compounds.
Related endogenous compounds | Amphetamine | Wikipedia | 502 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Amphetamine has a very similar structure and function to the endogenous trace amines, which are naturally occurring neuromodulator molecules produced in the human body and brain. Among this group, the most closely related compounds are phenethylamine, the parent compound of amphetamine, and , a structural isomer of amphetamine (i.e., it has an identical molecular formula). In humans, phenethylamine is produced directly from by the aromatic amino acid decarboxylase (AADC) enzyme, which converts into dopamine as well. In turn, is metabolized from phenethylamine by phenylethanolamine N-methyltransferase, the same enzyme that metabolizes norepinephrine into epinephrine. Like amphetamine, both phenethylamine and regulate monoamine neurotransmission via ; unlike amphetamine, both of these substances are broken down by monoamine oxidase B, and therefore have a shorter half-life than amphetamine.
Chemistry
Amphetamine is a methyl homolog of the mammalian neurotransmitter phenethylamine with the chemical formula . The carbon atom adjacent to the primary amine is a stereogenic center, and amphetamine is composed of a racemic 1:1 mixture of two enantiomers. This racemic mixture can be separated into its optical isomers: levoamphetamine and dextroamphetamine. At room temperature, the pure free base of amphetamine is a mobile, colorless, and volatile liquid with a characteristically strong amine odor, and acrid, burning taste. Frequently prepared solid salts of amphetamine include amphetamine adipate, aspartate, hydrochloride, phosphate, saccharate, sulfate, and tannate. Dextroamphetamine sulfate is the most common enantiopure salt. Amphetamine is also the parent compound of its own structural class, which includes a number of psychoactive derivatives. In organic chemistry, amphetamine is an excellent chiral ligand for the stereoselective synthesis of .
Substituted derivatives | Amphetamine | Wikipedia | 451 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
The substituted derivatives of amphetamine, or "substituted amphetamines", are a broad range of chemicals that contain amphetamine as a "backbone"; specifically, this chemical class includes derivative compounds that are formed by replacing one or more hydrogen atoms in the amphetamine core structure with substituents. The class includes amphetamine itself, stimulants like methamphetamine, serotonergic empathogens like MDMA, and decongestants like ephedrine, among other subgroups.
Synthesis
Since the first preparation was reported in 1887, numerous synthetic routes to amphetamine have been developed. The most common route of both legal and illicit amphetamine synthesis employs a non-metal reduction known as the Leuckart reaction (method 1). In the first step, a reaction between phenylacetone and formamide, either using additional formic acid or formamide itself as a reducing agent, yields . This intermediate is then hydrolyzed using hydrochloric acid, and subsequently basified, extracted with organic solvent, concentrated, and distilled to yield the free base. The free base is then dissolved in an organic solvent, sulfuric acid added, and amphetamine precipitates out as the sulfate salt.
A number of chiral resolutions have been developed to separate the two enantiomers of amphetamine. For example, racemic amphetamine can be treated with to form a diastereoisomeric salt which is fractionally crystallized to yield dextroamphetamine. Chiral resolution remains the most economical method for obtaining optically pure amphetamine on a large scale. In addition, several enantioselective syntheses of amphetamine have been developed. In one example, optically pure is condensed with phenylacetone to yield a chiral Schiff base. In the key step, this intermediate is reduced by catalytic hydrogenation with a transfer of chirality to the carbon atom alpha to the amino group. Cleavage of the benzylic amine bond by hydrogenation yields optically pure dextroamphetamine. | Amphetamine | Wikipedia | 438 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
A large number of alternative synthetic routes to amphetamine have been developed based on classic organic reactions. One example is the Friedel–Crafts alkylation of benzene by allyl chloride to yield beta chloropropylbenzene which is then reacted with ammonia to produce racemic amphetamine (method 2). Another example employs the Ritter reaction (method 3). In this route, allylbenzene is reacted acetonitrile in sulfuric acid to yield an organosulfate which in turn is treated with sodium hydroxide to give amphetamine via an acetamide intermediate. A third route starts with which through a double alkylation with methyl iodide followed by benzyl chloride can be converted into acid. This synthetic intermediate can be transformed into amphetamine using either a Hofmann or Curtius rearrangement (method 4).
A significant number of amphetamine syntheses feature a reduction of a nitro, imine, oxime, or other nitrogen-containing functional groups. In one such example, a Knoevenagel condensation of benzaldehyde with nitroethane yields . The double bond and nitro group of this intermediate is reduced using either catalytic hydrogenation or by treatment with lithium aluminium hydride (method 5). Another method is the reaction of phenylacetone with ammonia, producing an imine intermediate that is reduced to the primary amine using hydrogen over a palladium catalyst or lithium aluminum hydride (method 6). | Amphetamine | Wikipedia | 315 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Detection in body fluids
Amphetamine is frequently measured in urine or blood as part of a drug test for sports, employment, poisoning diagnostics, and forensics. Techniques such as immunoassay, which is the most common form of amphetamine test, may cross-react with a number of sympathomimetic drugs. Chromatographic methods specific for amphetamine are employed to prevent false positive results. Chiral separation techniques may be employed to help distinguish the source of the drug, whether prescription amphetamine, prescription amphetamine prodrugs, (e.g., selegiline), over-the-counter drug products that contain levomethamphetamine, or illicitly obtained substituted amphetamines. Several prescription drugs produce amphetamine as a metabolite, including benzphetamine, clobenzorex, famprofazone, fenproporex, lisdexamfetamine, mesocarb, methamphetamine, prenylamine, and selegiline, among others. These compounds may produce positive results for amphetamine on drug tests. Amphetamine is generally only detectable by a standard drug test for approximately 24 hours, although a high dose may be detectable for days.
For the assays, a study noted that an enzyme multiplied immunoassay technique (EMIT) assay for amphetamine and methamphetamine may produce more false positives than liquid chromatography–tandem mass spectrometry. Gas chromatography–mass spectrometry (GC–MS) of amphetamine and methamphetamine with the derivatizing agent chloride allows for the detection of methamphetamine in urine. GC–MS of amphetamine and methamphetamine with the chiral derivatizing agent Mosher's acid chloride allows for the detection of both dextroamphetamine and dextromethamphetamine in urine. Hence, the latter method may be used on samples that test positive using other methods to help distinguish between the various sources of the drug.
History, society, and culture | Amphetamine | Wikipedia | 454 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Amphetamine was first synthesized in 1887 in Germany by Romanian chemist Lazăr Edeleanu who named it phenylisopropylamine; its stimulant effects remained unknown until 1927, when it was independently resynthesized by Gordon Alles and reported to have sympathomimetic properties. Amphetamine had no medical use until late 1933, when Smith, Kline and French began selling it as an inhaler under the brand name Benzedrine as a decongestant. Benzedrine sulfate was introduced 3 years later and was used to treat a wide variety of medical conditions, including narcolepsy, obesity, low blood pressure, low libido, and chronic pain, among others. During World War II, amphetamine and methamphetamine were used extensively by both the Allied and Axis forces for their stimulant and performance-enhancing effects. As the addictive properties of the drug became known, governments began to place strict controls on the sale of amphetamine. For example, during the early 1970s in the United States, amphetamine became a schedule II controlled substance under the Controlled Substances Act. In spite of strict government controls, amphetamine has been used legally or illicitly by people from a variety of backgrounds, including authors, musicians, mathematicians, and athletes.
Amphetamine is illegally synthesized in clandestine labs and sold on the black market, primarily in European countries. Among European Union (EU) member states 11.9 million adults of ages have used amphetamine or methamphetamine at least once in their lives and 1.7 million have used either in the last year. During 2012, approximately 5.9 metric tons of illicit amphetamine were seized within EU member states; the "street price" of illicit amphetamine within the EU ranged from per gram during the same period. Outside Europe, the illicit market for amphetamine is much smaller than the market for methamphetamine and MDMA. | Amphetamine | Wikipedia | 408 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Legal status
As a result of the United Nations 1971 Convention on Psychotropic Substances, amphetamine became a schedule II controlled substance, as defined in the treaty, in all 183 state parties. Consequently, it is heavily regulated in most countries. Some countries, such as South Korea and Japan, have banned substituted amphetamines even for medical use. In other nations, such as Brazil (class A3), Canada (schedule I drug), the Netherlands (List I drug), the United States (schedule II drug), Australia (schedule 8), Thailand (category 1 narcotic), and United Kingdom (class B drug), amphetamine is in a restrictive national drug schedule that allows for its use as a medical treatment.
Pharmaceutical products
Several currently marketed amphetamine formulations contain both enantiomers, including those marketed under the brand names Adderall, Adderall XR, Mydayis, Adzenys ER, , Dyanavel XR, Evekeo, and Evekeo ODT. Of those, Evekeo (including Evekeo ODT) is the only product containing only racemic amphetamine (as amphetamine sulfate), and is therefore the only one whose active moiety can be accurately referred to simply as "amphetamine". Dextroamphetamine, marketed under the brand names Dexedrine and Zenzedi, is the only enantiopure amphetamine product currently available. A prodrug form of dextroamphetamine, lisdexamfetamine, is also available and is marketed under the brand name Vyvanse. As it is a prodrug, lisdexamfetamine is structurally different from dextroamphetamine, and is inactive until it metabolizes into dextroamphetamine. The free base of racemic amphetamine was previously available as Benzedrine, Psychedrine, and Sympatedrine. Levoamphetamine was previously available as Cydril. Many current amphetamine pharmaceuticals are salts due to the comparatively high volatility of the free base. However, oral suspension and orally disintegrating tablet (ODT) dosage forms composed of the free base were introduced in 2015 and 2016, respectively. Some of the current brands and their generic equivalents are listed below. | Amphetamine | Wikipedia | 486 | 2504 | https://en.wikipedia.org/wiki/Amphetamine | Biology and health sciences | Drugs and pharmacology | null |
Fieldnotes refer to qualitative notes recorded by scientists or researchers in the course of field research, during or after their observation of a specific organism or phenomenon they are studying. The notes are intended to be read as evidence that gives meaning and aids in the understanding of the phenomenon. Fieldnotes allow researchers to access the subject and record what they observe in an unobtrusive manner.
One major disadvantage of taking fieldnotes is that they are recorded by an observer and are thus subject to (a) memory and (b) possibly, the conscious or unconscious bias of the observer. It is best to record fieldnotes while making observations in the field or immediately after leaving the site to avoid forgetting important details. Some suggest immediately transcribing one's notes from a smaller pocket-sized notebook to something more legible in the evening or as soon as possible. Errors that occur from transcription often outweigh the errors which stem from illegible writing in the actual "field" notebook.
Fieldnotes are particularly valued in descriptive sciences such as ethnography, biology, ecology, geology, and archaeology, each of which has long traditions in this area.
Structure
The structure of fieldnotes can vary depending on the field. Generally, there are two components of fieldnotes: descriptive information and reflective information.
Descriptive information is factual data that is being recorded. Factual data includes time and date, the state of the physical setting, social environment, descriptions of the subjects being studied and their roles in the setting, and the impact that the observer may have had on the environment.
Reflective information is the observer's reflections about the observation being conducted. These reflections are ideas, questions, concerns, and other related thoughts.
Fieldnotes can also include sketches, diagrams, and other drawings. Visually capturing a phenomenon requires the observer to pay attention to every detail so as not to overlook anything. An author does not necessarily need to possess great artistic abilities to craft an exceptional note. In many cases, a rudimentary drawing or sketch can greatly assist in later data collection and synthesis. Increasingly, photographs may be included as part of a fieldnote when collected in a digital format.
Other observers may further subdivide the structure of fieldnotes. Nigel Rapport said that fieldnotes in anthropology transition rapidly among three types. | Fieldnotes | Wikipedia | 461 | 4083803 | https://en.wikipedia.org/wiki/Fieldnotes | Physical sciences | Research methods | Basics and measurement |
Inscription – where the writer records notes, impressions, and potentially important keywords.
Transcription – where the author writes down dictated local text
Description – a reflective type of writing that synthesizes previous observations and analysis for a later situation in which a more coherent conclusion can be made of the notes.
Value
Fieldnotes are extremely valuable for scientists at each step of their training. In an article on fieldnotes, James Van Remsen Jr. discussed the tragic loss of information from birdwatchers in his study area that could have been taking detailed fieldnotes but neglected to do so. This comment points to a larger issue regarding how often one should be taking fieldnotes. In this case, Remsen was upset because of the multitudes of "eyes and ears" that could have supplied potentially important information for his bird surveys but instead remained with the observers. Scientists like Remsen believe observations can be easily lost if notes are not taken.
Nature phone apps and digital citizen science databases (like eBird) are changing the form and frequency of field data collection and may contribute to de-emphasizing the importance of hand-written notes. Apps may open up new possibilities for citizen science, but taking time to handwrite fieldnotes can help with the synthesis of details that one may not remember as well from data entry in an app. Writing in such a detailed manner may contribute to the personal growth of a scientist.
Nigel Rapport, an anthropological field writer, said that fieldnotes are filled with the conventional realities of "two forms of life": local and academic. The lives are different and often contradictory but are often brought together through the efforts of a "field writer". The academic side refers to one's professional involvements, and fieldnotes take a certain official tone. The local side reflects more of the personal aspects of a writer and so the fieldnotes may also relate more to personal entries.
In biology and ecology
Taking fieldnotes in biology and other natural sciences will differ slightly from those taken in social sciences, as they may be limited to interactions regarding a focal species and/or subject. An example of an ornithological fieldnote was reported by Remsen (1977) regarding a sighting of a Cassin's sparrow, a relatively rare bird for the region where it was found.
Grinnell method of note-taking
An important teacher of efficient and accurate note-taking is Joseph Grinnell. The Grinnell technique has been regarded by many ornithologists as one of the best standardized methods for taking accurate fieldnotes. | Fieldnotes | Wikipedia | 508 | 4083803 | https://en.wikipedia.org/wiki/Fieldnotes | Physical sciences | Research methods | Basics and measurement |
The technique has four main parts:
A field-worthy notebook where one records direct observations as they are being observed.
A larger more substantial journal containing written entries on observations and information, transcribed from the smaller field notebook as soon as possible.
Species accounts of the notes taken on specific species.
A catalog to record the location and date of collected specimens.
In social sciences
Grounded theory
Methods for analyzing and integrating fieldnotes into qualitative or quantitative research are continuing to develop. Grounded theory is a method for integrating data in qualitative research done primarily by social scientists. This may have implications for fieldnotes in the natural sciences as well.
Considerations when recording fieldnotes
The decisions about choosing what is recorded may have a significant impact on the ultimate findings. As such, creating and adhering to a systematic method for recording fieldnotes is an important consideration for a qualitative research. American social scientist Robert K. Yin recommended the following considerations as best practices when recording qualitative field notes. | Fieldnotes | Wikipedia | 196 | 4083803 | https://en.wikipedia.org/wiki/Fieldnotes | Physical sciences | Research methods | Basics and measurement |
Create vivid images: Focus on recording vivid descriptions of actions that take place in the field, instead of recording an interpretation of them. This is particularly important early in the research process. Immediately trying to interpret events can lead to premature conclusions that can prevent later insight when more observation has occurred. Focusing on the actions taking place in the field, instead of trying to describe people or scenes, can be a useful tool to minimize personal stereotyping of the situation.
The verbatim principle: Similar to the vivid images, the goal is to accurately record what is happening in the field, not a personal paraphrasing (and possible unconscious stereotyping) of those events. Additionally, in social science research that involves studying culture, it is important to faithfully capture language and habits as a first step toward full understanding.
Include drawings and sketches: These can quickly and accurately capture important aspects of field activity that are difficult to record in words and can be very helpful for recall when reviewing fieldnotes.
Develop one's own transcribing language: While no one technique of transcribing (or "jotting") is perfect, most qualitative researchers develop a systematic approach to their own note-taking. Considering the multiple competing demands on attention (the simultaneous observation, processing, and recording of rich qualitative data in an unfamiliar environment), perfecting a system that can be automatically used and that will be interpretable later allows one to allocate one's full attention to observation. The ability to distinguish notes about events themselves from other notes to oneself is a key feature. Prior to engaging in qualitative research for the first time, practicing a transcribing format beforehand can improve the likelihood of successful observation.
Convert fieldnotes to full notes daily: Prior to discussing one's observations with anyone else, one should set aside time each day to convert fieldnotes. At the very least, any unclear abbreviations, illegible words, or unfinished thoughts should be completed that would be uninterpretable later. In addition, the opportunity to collect one's thoughts and reflect on that day's events can lead to recalling additional details, uncovering emerging themes, leading to new understanding, and helping plan for future observations. This is also a good time to add the day's notes to one's total collection in an organized manner. | Fieldnotes | Wikipedia | 479 | 4083803 | https://en.wikipedia.org/wiki/Fieldnotes | Physical sciences | Research methods | Basics and measurement |
Verify notes during collection: Converting fieldnotes as described above will likely lead the researcher to discover key points and themes that can then be checked while still present in the field. If conflicting themes are emerging, further data collection can be directed in a manner to help resolve the discrepancy.
Obtain permission to record: While electronic devices and audiovisual recording can be useful tools in performing field research, there are some common pitfalls to avoid. Ensure that permission is obtained for the use of these devices beforehand and ensure that the devices to be used for recording have been previously tested and can be used inconspicuously.
Keep a personal journal in addition to fieldnotes: As the researcher is the main instrument, insight into one's own reactions to and initial interpretations of events can help the researcher identify any undesired personal biases that might have influenced the research. This is useful for reflexivity. | Fieldnotes | Wikipedia | 181 | 4083803 | https://en.wikipedia.org/wiki/Fieldnotes | Physical sciences | Research methods | Basics and measurement |
The saltwater crocodile (Crocodylus porosus) is a crocodilian native to saltwater habitats, brackish wetlands and freshwater rivers from India's east coast across Southeast Asia and the Sundaland to northern Australia and Micronesia. It has been listed as Least Concern on the IUCN Red List since 1996. It was hunted for its skin throughout its range up to the 1970s, and is threatened by illegal killing and habitat loss. It is regarded as dangerous to humans.
The saltwater crocodile is the largest living reptile. Males can grow up to a weight of and a length of , rarely exceeding . Females are much smaller and rarely surpass . It is also called the estuarine crocodile, Indo-Pacific crocodile, marine crocodile, sea crocodile, and, informally, the saltie. A large and opportunistic hypercarnivorous apex predator, they ambush most of their prey and then drown or swallow it whole. They will prey on almost any animal that enters their territory, including other predators such as sharks, varieties of freshwater and saltwater fish including pelagic species, invertebrates such as crustaceans, various amphibians, other reptiles, birds, and mammals.
Taxonomy and evolution
Crocodilus porosus was the scientific name proposed by Johann Gottlob Theaenus Schneider who described a zoological specimen in 1801. In the 19th and 20th centuries, several saltwater crocodile specimens were described with the following names:
Crocodilus biporcatus proposed by Georges Cuvier in 1807 were 23 saltwater crocodile specimens from India, Java and Timor.
Crocodilus biporcatus raninus proposed by Salomon Müller and Hermann Schlegel in 1844 was a crocodile from Borneo.
Crocodylus porosus australis proposed by Paulus Edward Pieris Deraniyagala in 1953 was a specimen from Australia.
Crocodylus pethericki proposed by Richard Wells and C. Ross Wellington in 1985 was a large-bodied, relatively large-headed and short-tailed crocodile specimen collected in 1979 in the Finnis River, Northern Territory. This purported species was later considered to be a misinterpretation of the physiological changes that very large male crocodiles undergo. However, Wells and Wellington's assertion that the Australian saltwater crocodiles may be distinctive enough from northern Asian saltwater crocodiles to warrant subspecies status, as could raninus from other Asian saltwater crocodiles, has been considered to possibly bear validity. | Saltwater crocodile | Wikipedia | 507 | 566405 | https://en.wikipedia.org/wiki/Saltwater%20crocodile | Biology and health sciences | Crocodilia | Animals |
Currently, the saltwater crocodile is considered a monotypic species.
Evolution
Fossil remains of a saltwater crocodile excavated in northern Queensland were dated to the Pliocene. The saltwater crocodile's closest extant (living) relatives are the Siamese crocodile and the mugger crocodile.
The genus Crocodylus was thought to have evolved in Australia and Asia. Results of a phylogenetic study supports its likely origin in Africa and later radiation towards Southeast Asia and the Americas; it genetically diverged from its closest recent relative, the extinct Voay of Madagascar, around near the boundary between the Oligocene and Miocene.
Phylogeny
Below is a cladogram based on a 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data, as revised in 2021 after a paleogenomics study using DNA extracted from the extinct Voay.
Description
The saltwater crocodile has a wide snout compared to most crocodiles. However, it has a longer snout than the mugger crocodile (C. palustris); its length is twice its width at the base. A pair of ridges runs from the eyes along the centre of the snout. The scales are oval in shape and the scutes are either small compared to other species or commonly are entirely absent. In addition, an obvious gap is also present between the cervical and dorsal shields, and small, triangular scutes are present between the posterior edges of the large, transversely arranged scutes in the dorsal shield. The relative lack of scutes is considered an asset useful to distinguish saltwater crocodiles in captivity or in illicit leather trading, as well as in the few areas in the field where sub-adult or younger saltwater crocodiles may need to be distinguished from other crocodiles. It has fewer armour plates on its neck than other crocodilians.
The adult saltwater crocodile's broad body contrasts with that of most other lean crocodiles, leading to early unverified assumptions the reptile was an alligator. | Saltwater crocodile | Wikipedia | 416 | 566405 | https://en.wikipedia.org/wiki/Saltwater%20crocodile | Biology and health sciences | Crocodilia | Animals |
Young saltwater crocodiles are pale yellow in colour with black stripes and spots on their bodies and tails. This colouration lasts for several years until the crocodiles mature into adults. The colour as an adult is much darker greenish-drab, with a few lighter tan or grey areas sometimes apparent. Several colour variations are known and some adults may retain fairly pale skin, whereas others may be so dark as to appear blackish. The ventral surface is white or yellow in colour in saltwater crocodiles of all ages. Stripes are present on the lower sides of their bodies, but do not extend onto their bellies. Their tails are grey with dark bands.
Size
The weight of a crocodile increases approximately cubically as length increases (see square–cube law). This explains why individuals at weigh more than twice as much as individuals at . In crocodiles, linear growth eventually decreases and they start getting bulkier at a certain point.
Saltwater crocodiles are the largest extant riparian predators in the world. However, they start life fairly small. Newly hatched saltwater crocodiles measure about long and weigh an average of . These sizes and ages are almost identical to those at average sexual maturity in Nile crocodiles, despite the fact that average adult male saltwater crocodiles are considerably larger than average adult male Nile crocodiles.
The largest skull of a saltwater crocodile that could be scientifically verified was of a specimen in the Muséum national d'Histoire naturelle, collected in Cambodia. Its skull was long and wide near its base, with long mandibles; its length is not known, but based on skull-to-length ratios of large saltwater crocodiles its length was presumably in the range, though it could have had an exceptionally large skull or may not have the same skull-to-total-length ratios as other large saltwater crocodiles. If detached from the body, the head of a large male crocodile can weigh over , including the large muscles and tendons at the base of the skull that lend the crocodile its massive biting strength. The largest tooth measured in length.
Other crocodilians like the gharial (Gavialis gangeticus) and the false gharial (Tomistoma schlegelii) have a proportionately longer skull, but both their skulls and their bodies are less massive than in the saltwater crocodile. | Saltwater crocodile | Wikipedia | 478 | 566405 | https://en.wikipedia.org/wiki/Saltwater%20crocodile | Biology and health sciences | Crocodilia | Animals |
Male size
An adult male saltwater crocodile, from young adults to older individuals, typically ranges in length and weighs . On average, adult males range in length and weigh . However average size largely depends on the location, habitat, and human interactions and thus varies from one study to another. In 1993, in a study conducted (published in 1998), eleven saltwater crocodiles were found to have measured and weighed between . Very large, aged males can exceed in length and presumably weigh up to . | Saltwater crocodile | Wikipedia | 99 | 566405 | https://en.wikipedia.org/wiki/Saltwater%20crocodile | Biology and health sciences | Crocodilia | Animals |
The largest confirmed saltwater crocodile on record drowned in a fishing net in Papua New Guinea, in 1979. Its dried skin plus head measured in length and it was estimated to have been when accounting for shrinkage and a missing tail tip. Projected from their skull lengths, multiple specimens from Singapore were estimated to belong in life to male crocodiles measuring more than . A large Vietnamese saltwater crocodile was reliably estimated, based on its skull after its death, at . However, according to evidence in the form of skulls coming from some of the largest crocodiles ever shot, the maximum possible size attained by the largest members of this species is considered to be . A governmental study from Australia accepts that the very largest members of the species are likely to measure in length and weigh . Furthermore, a research paper on the morphology and physiology of crocodilians by the same organisation estimates that saltwater crocodiles reaching sizes of would weigh around . Due to the extreme size and highly aggressive nature of the species, weight in larger specimens is frequently poorly documented. A long individual named "Sweetheart" was found to have weighed . Another large crocodile named "Gomek", measuring in length weighed around . In 1992, a notorious man-eater, named "Bujang Senang" was killed in Sarawak, Malaysia. It measured in length and weighed more than . A saltwater–siamese hybrid named "Yai" (, meaning big; born 10 June 1972) at the Samutprakarn Crocodile Farm and Zoo, Thailand was claimed to be the largest crocodile ever held in captivity. It measured in length and weighed approximately . In 1962, a large male saltwater crocodile was shot in Adelaide River, Northern Territory. It was recorded to be long and weighed . A large male in the Philippines, named Lolong, was one of the largest saltwater crocodile ever caught and placed in captivity. He was long and weighed . Following his death in 2013, the largest living crocodile in captivity was "Cassius", who was kept at Marineland Crocodile Park, a zoo located at Green Island, Queensland, Australia. He measured 5.48 m (18 ft 0 in) in length and weighed approximately 1,300 kg (2,870 lb) before his own death in November 2024. | Saltwater crocodile | Wikipedia | 459 | 566405 | https://en.wikipedia.org/wiki/Saltwater%20crocodile | Biology and health sciences | Crocodilia | Animals |
Female size
Adult females typically measure from in total length and weigh . Large mature females reach and weigh up to . The largest female on record measured about in total length. Female are thus similar in size to other species of large crocodiles and average slightly smaller than females of some other species, like the Nile crocodile. The saltwater crocodile has the greatest size sexual dimorphism, by far, of any extant crocodilian, as males average about 4 to 5 times as massive as adult females and can sometimes measure twice her total length. The reason for the male skewered dimorphism in this species is not definitively known but might be correlated with sex-specific territoriality and the need for adult male saltwater crocodiles to monopolise large stretches of habitat. Due to the extreme sexual dimorphism of the species as contrasted with the more modest-sized dimorphism of other species, the average length of the species is only slightly more than some other extant crocodilians at .
Reported sizes
Distribution and habitat
The saltwater crocodile inhabits coastal brackish mangrove swamps, river deltas and freshwater rivers from India's east coast, Sri Lanka and Bangladesh to Myanmar, Malaysia, Brunei, Indonesia, Philippines, Timor Leste, Palau, Solomon Islands, Singapore, Papua New Guinea, Vanuatu and Australia's north coast. The southernmost population in India lives in Odisha's Bhitarkanika Wildlife Sanctuary; in northern Odisha, it has not been recorded since the 1930s. It occurs along the Andaman and Nicobar Islands coasts and in the Sundarbans. In Sri Lanka, it occurs foremost in western and southern parts of the country.
In Myanmar, it inhabits the Ayeyarwady Delta.
In southern Thailand, it was recorded in Phang Nga Province.
In Singapore, it inhabits the Sungei Buloh Wetland Reserve and marshes near Kranji and Mandai. It is locally extinct in Cambodia, China, Seychelles, Thailand and Vietnam.
In China, it may have once inhabited coastal areas from Fujian province in the north to the border of Vietnam. | Saltwater crocodile | Wikipedia | 430 | 566405 | https://en.wikipedia.org/wiki/Saltwater%20crocodile | Biology and health sciences | Crocodilia | Animals |
Bait is any appetizing substance (e.g. food) used to attract prey when hunting or fishing, most commonly in the form of trapping (e.g. mousetrap and bird trap), ambushing (e.g. from a hunting blind) and angling.
Baiting is a ubiquitous practice in both recreational (especially angling) and commercial fishing, but the use of live bait can be deemed illegal under certain fisheries law and local jurisdictions. For hunting, however, baiting can often be controversial as it violates the principles of fair chase, although it is still a commonly accepted practice in varmint hunting, culling and pest control.
Uses
Fishing
Baiting is ubiquitously practised to catching fish. Traditionally, nightcrawlers, small baitfish, insect adults and larvae have been used as standard hookbait, and offals are commonly used as groundbait (a.k.a. chumming) in blue water fishing. Modern fishermen have also begun using more plastic bait and lures, and more recently, electronic bionic baits, to attract the more territorial and aggressive predatory fishes. Because of the risk of transmitting Myxobolus cerebralis (whirling disease), trout and salmon should not be used as bait. There are various types of natural saltwater bait. Studies show that natural baits like croaker and shrimp are better recognized therefore more readily accepted by fish. The best bait for red drum (red fish) are [ pogy (menhaden) and, in the fall, specks like croaker.
Hunting
Baiting is a common practice in leopard hunting on a safari. A dead, smaller-sized antelope is usually placed high in the tree to lure the otherwise overcautious leopard. The hunter either watches the bait from point within firing range or stalks the animal if it has come for the bait during the night.
In areas where bears are hunted, bait can be found for sale at gas stations and hunting supply stores. Often consisting of some sweet substance, such as frosting or molasses, combined with an aromatic like rotten meat or fish, the bait is spread and the hunter waits under cover for his prey.
Cecil the Lion, who was infamously poached by an American trophy bowhunter in 2015, was baited out of the protected area into an ambush at the margin of a private land by a deliberately planted elephant carcass.
Pest control | Bait (luring substance) | Wikipedia | 500 | 566692 | https://en.wikipedia.org/wiki/Bait%20%28luring%20substance%29 | Technology | Hunting and fishing | null |
Poisoned bait is a common method for controlling rats, mice, birds, slugs, snails, ants, cockroaches, and other pests. The basic granules, or other formulation, contains a food attractant for the target species and a suitable poison. For ants, a slow-acting toxin is needed so that the workers have time to carry the substance back to the colony, and for flies, a quick-acting substance to prevent further egg-laying and nuisance. Baits for slugs and snails often contain the molluscide metaldehyde, dangerous to children and household pets.
Legal usage
In Australia
Baiting in Australia refers to specific campaigns to control foxes, wild dogs and dingos by poisoning in areas where they are a problem. These programs are held in conjunction with the local Department of Primary Industries, Rural Lands Protection Board (RLPB) and National Parks and Wildlife Service (NPWS) to facilitate a neighbourhood baiting campaign.
Australian hunters often use carcasses when hunting feral pigs. Shot feral animals are often left in the field, and the decaying smell attracts more pigs to scavenge over the subsequent days. | Bait (luring substance) | Wikipedia | 233 | 566692 | https://en.wikipedia.org/wiki/Bait%20%28luring%20substance%29 | Technology | Hunting and fishing | null |
In electrochemistry, standard electrode potential , or , is a measure of the reducing power of any element or compound. The IUPAC "Gold Book" defines it as; "the value of the standard emf (electromotive force) of a cell in which molecular hydrogen under standard pressure is oxidized to solvated protons at the left-hand electrode".
Background
The basis for an electrochemical cell, such as the galvanic cell, is always a redox reaction which can be broken down into two half-reactions: oxidation at anode (loss of electron) and reduction at cathode (gain of electron). Electricity is produced due to the difference of electric potential between the individual potentials of the two metal electrodes with respect to the electrolyte.
Although the overall potential of a cell can be measured, there is no simple way to accurately measure the electrode/electrolyte potentials in isolation. The electric potential also varies with temperature, concentration and pressure. Since the oxidation potential of a half-reaction is the negative of the reduction potential in a redox reaction, it is sufficient to calculate either one of the potentials. Therefore, standard electrode potential is commonly written as standard reduction potential.
Calculation
The galvanic cell potential results from the voltage difference of a pair of electrodes. It is not possible to measure an absolute value for each electrode separately. However, the potential of a reference electrode, standard hydrogen electrode (SHE), is defined as to 0.00 V. An electrode with unknown electrode potential can be paired with either the standard hydrogen electrode, or another electrode whose potential has already been measured, to determine its "absolute" potential.
Since the electrode potentials are conventionally defined as reduction potentials, the sign of the potential for the metal electrode being oxidized must be reversed when calculating the overall cell potential. The electrode potentials are independent of the number of electrons transferred —they are expressed in volts, which measure energy per electron transferred—and so the two electrode potentials can be simply combined to give the overall cell potential even if different numbers of electrons are involved in the two electrode reactions.
For practical measurements, the electrode in question is connected to the positive terminal of the electrometer, while the standard hydrogen electrode is connected to the negative terminal.
Reversible electrode | Standard electrode potential | Wikipedia | 473 | 566959 | https://en.wikipedia.org/wiki/Standard%20electrode%20potential | Physical sciences | Electrochemistry | Chemistry |
A reversible electrode is an electrode that owes its potential to changes of a reversible nature. A first condition to be fulfilled is that the system is close to the chemical equilibrium. A second set of conditions is that the system is submitted to very small solicitations spread on a sufficient period of time so, that the chemical equilibrium conditions nearly always prevail. In theory, it is very difficult to experimentally achieve reversible conditions because any perturbation imposed to a system near equilibrium in a finite time forces it out of equilibrium. However, if the solicitations exerted on the system are sufficiently small and applied slowly, one can consider an electrode to be reversible. By nature, electrode reversibility depends on the experimental conditions and the way the electrode is operated. For example, electrodes used in electroplating are operated with a high over-potential to force the reduction of a given metal cation to be deposited onto a metallic surface to be protected. Such a system is far from equilibrium and continuously submitted to important and constant changes in a short period of time
Standard reduction potential table
The larger the value of the standard reduction potential, the easier it is for the element to be reduced (gain electrons); in other words, they are better oxidizing agents.
For example, F2 has a standard reduction potential of +2.87 V and Li+ has −3.05 V:
(g) + 2 2 = +2.87 V
+ (s) = −3.05 V
The highly positive standard reduction potential of F2 means it is reduced easily and is therefore a good oxidizing agent. In contrast, the greatly negative standard reduction potential of Li+ indicates that it is not easily reduced. Instead, Li(s) would rather undergo oxidation (hence it is a good reducing agent).
Zn2+ has a standard reduction potential of −0.76 V and thus can be oxidized by any other electrode whose standard reduction potential is greater than −0.76 V (e.g., H+ (0 V), Cu2+ (0.34 V), F2 (2.87 V)) and can be reduced by any electrode with standard reduction potential less than −0.76 V (e.g. H2 (−2.23 V), Na+ (−2.71 V), Li+ (−3.05 V)). | Standard electrode potential | Wikipedia | 500 | 566959 | https://en.wikipedia.org/wiki/Standard%20electrode%20potential | Physical sciences | Electrochemistry | Chemistry |
In a galvanic cell, where a spontaneous redox reaction drives the cell to produce an electric potential, Gibbs free energy must be negative, in accordance with the following equation:
(unit: Joule = Coulomb × Volt)
where is number of moles of electrons per mole of products and is the Faraday constant, .
As such, the following rules apply:
If > 0, then the process is spontaneous (galvanic cell): < 0, and energy is liberated.
If < 0, then the process is non-spontaneous (electrolytic cell): > 0, and energy is consumed.
Thus in order to have a spontaneous reaction ( < 0), must be positive, where:
where is the standard potential at the cathode (called as standard cathodic potential or standard reduction potential and is the standard potential at the anode (called as standard anodic potential or standard oxidation potential) as given in the table of standard electrode potential. | Standard electrode potential | Wikipedia | 200 | 566959 | https://en.wikipedia.org/wiki/Standard%20electrode%20potential | Physical sciences | Electrochemistry | Chemistry |
The sea otter (Enhydra lutris) is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of the weasel family, but among the smallest marine mammals. Unlike most marine mammals, the sea otter's primary form of insulation is an exceptionally thick coat of fur, the densest in the animal kingdom. Although it can walk on land, the sea otter is capable of living exclusively in the ocean.
The sea otter inhabits nearshore environments, where it dives to the sea floor to forage. It preys mostly on marine invertebrates such as sea urchins, various mollusks and crustaceans, and some species of fish. Its foraging and eating habits are noteworthy in several respects. Its use of rocks to dislodge prey and to open shells makes it one of the few mammal species to use tools. In most of its range, it is a keystone species, controlling sea urchin populations which would otherwise inflict extensive damage to kelp forest ecosystems. Its diet includes prey species that are also valued by humans as food, leading to conflicts between sea otters and fisheries.
Sea otters, whose numbers were once estimated at 150,000–300,000, were hunted extensively for their fur between 1741 and 1911, and the world population fell to 1,000–2,000 individuals living in a fraction of their historic range. A subsequent international ban on hunting, sea otter conservation efforts, and reintroduction programs into previously populated areas have contributed to numbers rebounding, and the species occupies about two-thirds of its former range. The recovery of the sea otter is considered an important success in marine conservation, although populations in the Aleutian Islands and California have recently declined or have plateaued at depressed levels. For these reasons, the sea otter remains classified as an endangered species. | Sea otter | Wikipedia | 385 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Evolution
The sea otter is the heaviest (the giant otter is longer, but significantly slimmer) member of the family Mustelidae, a diverse group that includes the 13 otter species and terrestrial animals such as weasels, badgers, and minks. It is unique among the mustelids in not making dens or burrows, in having no functional anal scent glands, and in being able to live its entire life without leaving the water. The only living member of the genus Enhydra, the sea otter is so different from other mustelid species that, as recently as 1982, some scientists believed it was more closely related to the earless seals. Genetic analysis indicates the sea otter and its closest extant relatives, which include the African speckle-throated otter, Eurasian otter, African clawless otter and Asian small-clawed otter, shared an ancestor approximately 5 million years ago. | Sea otter | Wikipedia | 179 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Fossil evidence indicates the Enhydra lineage became isolated in the North Pacific approximately 2 million years ago, giving rise to the now-extinct Enhydra macrodonta and the modern sea otter, Enhydra lutris. One related species has been described, Enhydra reevei, from the Pleistocene of East Anglia. The modern sea otter evolved initially in northern Hokkaidō and Russia, and then spread east to the Aleutian Islands, mainland Alaska, and down the North American coast. In comparison to cetaceans, sirenians, and pinnipeds, which entered the water approximately 50, 40, and 20 million years ago, respectively, the sea otter is a relative newcomer to a marine existence. In some respects, though, the sea otter is more fully adapted to water than pinnipeds, which must haul out on land or ice to give birth. The full genome of the northern sea otter (Enhydra lutris kenyoni) was sequenced in 2017 and may allow for examination of the sea otter's evolutionary divergence from terrestrial mustelids.
Following their divergence from their most common ancestor five million years ago, sea otters have developed traits dependent on polygenic selection, or the evolution of numerous traits to create hallmark features like thick and oily fur and large bones, compared to their freshwater sister species. Sea otters require these traits to survive the cold waters of the northern Pacific Ocean, in which they spend their entire lives despite occasionally coming out of the water as pups. Sea otters have the thickest fur of any animal (~1,000,000 hairs per square inch), as they do not have a blubber layer, while their oil glands help matt down their fur and keep it from holding air. Thick bones also prove crucial in increasing buoyancy, as sea otters spend long hours floating atop the ocean. In a study, southern and northern Sea Otter populations were compared against the African clawless otter, and it was determined that aquatic traits like loss of smell and hair thickness independently evolved, evidencing a complex genome of polygenic traits resulting in complex systems. This study was only able to take place after sequencing of Sea Otter nuclear genomes and through phylogeny to find a close ancestor with which to compare genomes. | Sea otter | Wikipedia | 469 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Previously, it was suspected that sea otters came from the same evolutionary branch as earless seals, such as harbor and monk seals. Sea Otters have experienced numerous population bottlenecks throughout their history, with significant numbers being wiped out 9,000-10,000 generations ago and 300–700 generations ago, long before the fur trade. These previous genetic bottlenecks are responsible for already low genetic diversity amongst species members, making the secondary bottleneck caused by the fur trade more significant. These primary bottlenecks were most likely caused by disease, a common cause for genetic bottlenecks. Estimates place these bottlenecks at leaving around ten to forty animals for about eight to forty-four years. This led to genetic drift, as the populations of northern and southern sea otters were cut off from one another by thousands of miles, leading to significant genomic differences. However, the modern population bottleneck caused by the fur trade of the eighteenth and early twentieth centuries presents the most significant concern to scientists and conservationists attempting to recover population numbers and genetic diversity. Each bottleneck has lowered genomic diversity and thus increased the chance of deleterious genetic drift.
Taxonomy
The first scientific description of the sea otter is contained in the field notes of Georg Steller from 1751, and the species was described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae. Originally named Lutra marina, it underwent numerous name changes before being accepted as Enhydra lutris in 1922. The generic name Enhydra, derives from the Ancient Greek en/εν "in" and hydra/ύδρα "water", meaning "in the water", and the Latin word lutris, meaning "otter". It was formerly sometimes referred to as the "sea beaver". | Sea otter | Wikipedia | 364 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Subspecies
Three subspecies of the sea otter are recognized with distinct geographical distributions. Enhydra lutris lutris (nominate), the Asian sea otter, ranges across Russia's Kuril Islands northeast of Japan, and the Commander Islands in the northwestern Pacific Ocean. In the eastern Pacific Ocean, E. l. kenyoni, the northern sea otter, is found from Alaska's Aleutian Islands to Oregon and E. l. nereis, the southern sea otter, is native to central and southern California. The Asian sea otter is the largest subspecies and has a slightly wider skull and shorter nasal bones than both other subspecies. Northern sea otters possess longer mandibles (lower jaws) while southern sea otters have longer rostrums and smaller teeth.
Description
The sea otter is one of the smallest marine mammal species, but it is the heaviest mustelid. Male sea otters usually weigh and are in length, though specimens up to have been recorded. Females are smaller, weighing and measuring in length. The average weight for adult sea otters that are in more densely populated areas, at in males and in females, was considerably lighter than the average weight of otters in more sparse populations, at in males and in females Presumably less populous otters are more able to monopolize food sources, For its size, the male otter's baculum is very large, massive and bent upwards, measuring in length and at the base. | Sea otter | Wikipedia | 297 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Unlike most other marine mammals, the sea otter has no blubber and relies on its exceptionally thick fur to keep warm. With up to , its fur is the densest of any animal. The fur consists of long, waterproof guard hairs and short underfur; the guard hairs keep the dense underfur layer dry. There is an air compartment between the thick fur and the skin where air is trapped and heated by the body. Cold water is kept completely away from the skin and heat loss is limited. However, a potential disadvantage of this form of insulation is compression of the air layer as the otter dives, thereby reducing the insulating quality of fur at depth when the animal forages. The fur is thick year-round, as it is shed and replaced gradually rather than in a distinct molting season. As the ability of the guard hairs to repel water depends on utmost cleanliness, the sea otter has the ability to reach and groom the fur on any part of its body, taking advantage of its loose skin and an unusually supple skeleton. The coloration of the pelage is usually deep brown with silver-gray speckles, but it can range from yellowish or grayish brown to almost black. In adults, the head, throat, and chest are lighter in color than the rest of the body.
The sea otter displays numerous adaptations to its marine environment. The nostrils and small ears can close. The hind feet, which provide most of its propulsion in swimming, are long, broadly flattened, and fully webbed. The fifth digit on each hind foot is longest, facilitating swimming while on its back, but making walking difficult. The tail is fairly short, thick, slightly flattened, and muscular. The front paws are short with retractable claws, with tough pads on the palms that enable gripping slippery prey. The bones show osteosclerosis, increasing their density to reduce buoyancy. | Sea otter | Wikipedia | 387 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
The sea otter presents an insight into the evolutionary process of the mammalian invasion of the aquatic environment, which has occurred numerous times over the course of mammalian evolution. Having only returned to the sea about 3 million years ago, sea otters represent a snapshot at the earliest point of the transition from fur to blubber. In sea otters, fur is still advantageous, given their small nature and division of lifetime between the aquatic and terrestrial environments. However, as sea otters evolve and adapt to spending more and more of their lifetimes in the sea, the convergent evolution of blubber suggests that the reliance on fur for insulation would be replaced by a dependency on blubber. This is particularly true due to the diving nature of the sea otter; as dives become lengthier and deeper, the air layer's ability to retain heat or buoyancy decreases, while blubber remains efficient at both of those functions. Blubber can also additionally serve as an energy source for deep dives, which would most likely prove advantageous over fur in the evolutionary future of sea otters.
The sea otter propels itself underwater by moving the rear end of its body, including its tail and hind feet, up and down, and is capable of speeds of up to . When underwater, its body is long and streamlined, with the short forelimbs pressed closely against the chest. When at the surface, it usually floats on its back and moves by sculling its feet and tail from side to side. At rest, all four limbs can be folded onto the torso to conserve heat, whereas on particularly hot days, the hind feet may be held underwater for cooling. The sea otter's body is highly buoyant because of its large lung capacity – about 2.5 times greater than that of similar-sized land mammals – and the air trapped in its fur. The sea otter walks with a clumsy, rolling gait on land, and can run in a bounding motion.
Long, highly sensitive whiskers and front paws help the sea otter find prey by touch when waters are dark or murky. Researchers have noted when they approach in plain view, sea otters react more rapidly when the wind is blowing towards the animals, indicating the sense of smell is more important than sight as a warning sense. Other observations indicate the sea otter's sense of sight is useful above and below the water, although not as good as that of seals. Its hearing is neither particularly acute nor poor. | Sea otter | Wikipedia | 501 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
An adult's 32 teeth, particularly the molars, are flattened and rounded for crushing rather than cutting food. Seals and sea otters are the only carnivores with two pairs of lower incisor teeth rather than three; the adult dental formula is . The teeth and bones are sometimes stained purple as a result of ingesting sea urchins.
The sea otter has a metabolic rate two or three times that of comparatively sized terrestrial mammals. It must eat an estimated 25 to 38% of its own body weight in food each day to burn the calories necessary to counteract the loss of heat due to the cold water environment. Its digestive efficiency is estimated at 80 to 85%, and food is digested and passed in as little as three hours. Most of its need for water is met through food, although, in contrast to most other marine mammals, it also drinks seawater. Its relatively large kidneys enable it to derive fresh water from sea water and excrete concentrated urine.
Behavior
The sea otter is diurnal. It has a period of foraging and eating in the morning, starting about an hour before sunrise, then rests or sleeps in mid-day. Foraging resumes for a few hours in the afternoon and subsides before sunset, and a third foraging period may occur around midnight. Females with pups appear to be more inclined to feed at night. Observations of the amount of time a sea otter must spend each day foraging range from 24 to 60%, apparently depending on the availability of food in the area.
Sea otters spend much of their time grooming, which consists of cleaning the fur, untangling knots, removing loose fur, rubbing the fur to squeeze out water and introduce air, and blowing air into the fur. To casual observers, it appears as if the animals are scratching, but they are not known to have lice or other parasites in the fur. When eating, sea otters roll in the water frequently, apparently to wash food scraps from their fur.
Foraging | Sea otter | Wikipedia | 411 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
The sea otter hunts in short dives, often to the sea floor. Although it can hold its breath for up to five minutes, its dives typically last about one minute and not more than four minutes. It is the only marine animal capable of lifting and turning over rocks, which it often does with its front paws when searching for prey. The sea otter may also pluck snails and other organisms from kelp and dig deep into underwater mud for clams. It is the only marine mammal that catches fish with its forepaws rather than with its teeth.
Under each foreleg, the sea otter has a loose pouch of skin that extends across the chest. In this pouch (preferentially the left one), the animal stores collected food to bring to the surface. This pouch also holds a rock, unique to the otter, that is used to break open shellfish and clams. At the surface, the sea otter eats while floating on its back, using its forepaws to tear food apart and bring it to its mouth. It can chew and swallow small mussels with their shells, whereas large mussel shells may be twisted apart. It uses its lower incisor teeth to access the meat in shellfish.
To eat large sea urchins, which are mostly covered with spines, the sea otter bites through the underside where the spines are shortest, and licks the soft contents out of the urchin's shell.
The sea otter's use of rocks when hunting and feeding makes it one of the few mammal species to use tools. To open hard shells, it may pound its prey with both paws against a rock on its chest. To pry an abalone off its rock, it hammers the abalone shell using a large stone, with observed rates of 45 blows in 15 seconds. Releasing an abalone, which can cling to rock with a force equal to 4,000 times its own body weight, requires multiple dives.
Social structure
Although each adult and independent juvenile forages alone, sea otters tend to rest together in single-sex groups called rafts. A raft typically contains 10 to 100 animals, with male rafts being larger than female ones. The largest raft ever seen contained over 2000 sea otters. To keep themselves from drifting out to sea when resting and eating, sea otters may wrap themselves in kelp. | Sea otter | Wikipedia | 479 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
A male sea otter is most likely to mate if he maintains a breeding territory in an area that is also favored by females. As autumn is the peak breeding season in most areas, males typically defend their territory only from spring to autumn. During this time, males patrol the boundaries of their territories to exclude other males, although actual fighting is rare. Adult females move freely between male territories, where they outnumber adult males by an average of five to one. Males that do not have territories tend to congregate in large, male-only groups, and swim through female areas when searching for a mate.
The species exhibits a variety of vocal behaviors. The cry of a pup is often compared to that of a gull. Females coo when they are apparently content; males may grunt instead. Distressed or frightened adults may whistle, hiss, or in extreme circumstances, scream. Although sea otters can be playful and sociable, they are not considered to be truly social animals. They spend much time alone, and each adult can meet its own hunting, grooming, and defense needs.
Reproduction and life cycle
Sea otters are polygynous: males have multiple female partners, typically those that inhabit their territory. If no territory is established, they seek out females in estrus. When a male sea otter finds a receptive female, the two engage in playful and sometimes aggressive behavior. They bond for the duration of estrus, or 3 days. The male holds the female's head or nose with his jaws during copulation. Visible scars are often present on females from this behavior.
Births occur year-round, with peaks between May and June in northern populations and between January and March in southern populations. Gestation appears to vary from four to twelve months, as the species is capable of delayed implantation followed by four months of pregnancy. In California, sea otters usually breed every year, about twice as often as those in Alaska.
Birth usually takes place in the water and typically produces a single pup weighing . Twins occur in 2% of births; however, usually only one pup survives. At birth, the eyes are open, ten teeth are visible, and the pup has a thick coat of baby fur. Mothers have been observed to lick and fluff a newborn for hours; after grooming, the pup's fur retains so much air, the pup floats like a cork and cannot dive. The fluffy baby fur is replaced by adult fur after about 13 weeks. | Sea otter | Wikipedia | 498 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Nursing lasts six to eight months in Californian populations and four to twelve months in Alaska, with the mother beginning to offer bits of prey at one to two months. The milk from a sea otter's two abdominal nipples is rich in fat and more similar to the milk of other marine mammals than to that of other mustelids. A pup, with guidance from its mother, practices swimming and diving for several weeks before it is able to reach the sea floor. Initially, the objects it retrieves are of little food value, such as brightly colored starfish and pebbles. Juveniles are typically independent at six to eight months, but a mother may be forced to abandon a pup if she cannot find enough food for it; at the other extreme, a pup may be nursed until it is almost adult size. Pup mortality is high, particularly during an individual's first winter – by one estimate, only 25% of pups survive their first year. Pups born to experienced mothers have the highest survival rates.
Females perform all tasks of feeding and raising offspring, and have occasionally been observed caring for orphaned pups. Much has been written about the level of devotion of sea otter mothers for their pups – a mother gives her infant almost constant attention, cradling it on her chest away from the cold water and attentively grooming its fur. When foraging, she leaves her pup floating on the water, sometimes wrapped in kelp to keep it from floating away; if the pup is not sleeping, it cries loudly until she returns. Mothers have been known to carry their pups for days after the pups' deaths.
Females become sexually mature at around three or four years of age and males at around five; however, males often do not successfully breed until a few years later. A captive male sired offspring at age 19. In the wild, sea otters live to a maximum age of 23 years, with lifespans ranging from 10 to 15 years for males and 15–20 years for females. Several captive individuals have lived past 20 years. The Seattle Aquarium was home to both the oldest recorded female, Etika, who lived to the age of 28, and the oldest recorded male, Adaa, who lived to be 22 years 8 months. Sea otters in the wild often develop worn teeth, which may account for their apparently shorter lifespans.
Population and distribution | Sea otter | Wikipedia | 478 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Sea otters live in coastal waters deep, and usually stay within a kilometre ( mi) of the shore. They are found most often in areas with protection from the most severe ocean winds, such as rocky coastlines, thick kelp forests, and barrier reefs. Although they are most strongly associated with rocky substrates, sea otters can also live in areas where the sea floor consists primarily of mud, sand, or silt. Their northern range is limited by ice, as sea otters can survive amidst drift ice but not land-fast ice. Individuals generally occupy a home range a few kilometres long, and remain there year-round.
The sea otter population is thought to have once been 150,000 to 300,000, stretching in an arc across the North Pacific from northern Japan to the central Baja California Peninsula in Mexico. The fur trade that began in the 1740s reduced the sea otter's numbers to an estimated 1,000 to 2,000 members in 13 colonies. Hunting records researched by historian Adele Ogden place the westernmost limit of the hunting grounds off the northern Japanese island of Hokkaido and the easternmost limit off Punta Morro Hermosa about south of Punta Eugenia, Baja California's westernmost headland in Mexico.
In about two-thirds of its former range, the species is at varying levels of recovery, with high population densities in some areas and threatened populations in others. Sea otters currently have stable populations in parts of the Russian east coast, Alaska, British Columbia, Washington, and California, with reports of recolonizations in Mexico and Japan. Population estimates made between 2004 and 2007 give a worldwide total of approximately 107,000 sea otters.
Japan
Adele Ogden wrote in The California Sea Otter Trade that western sea otter were hunted "from Yezo northeastward past the Kuril Group and Kamchatka to the Aleutian Chain". "Yezo" refers to the island province of Hokkaido, in northern Japan, where the country's only confirmed population of western sea otter resides. Sightings have been documented in the waters of Cape Nosappu, Erimo, Hamanaka and Nemuro, among other locations in the region. | Sea otter | Wikipedia | 443 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Russia
Currently, the most stable and secure part of the western sea otter's range is along the Russian Far East coastline, in the northwestern Pacific waters off of the country (namely Kamchatka and Sakhalin Island), occasionally being seen in and around the Sea of Okhotsk. Before the 19th century, around 20,000 to 25,000 sea otters lived near the Kuril Islands, with more near Kamchatka and the Commander Islands. After the years of the Great Hunt, the population in these areas, currently part of Russia, was only 750. By 2004, sea otters had repopulated all of their former habitat in these areas, with an estimated total population of about 27,000. Of these, about 19,000 are at the Kurils, 2,000 to 3,500 at Kamchatka and another 5,000 to 5,500 at the Commander Islands. Growth has slowed slightly, suggesting the numbers are reaching carrying capacity.
British Columbia
Along the North American coast south of Alaska, the sea otter's range is discontinuous. A remnant population survived off Vancouver Island into the 20th century, but it died out despite the 1911 international protection treaty, with the last sea otter taken near Kyuquot in 1929. From 1969 to 1972, 89 sea otters were flown or shipped from Alaska to the west coast of Vancouver Island. This population increased to over 5,600 in 2013 with an estimated annual growth rate of 7.2%, and their range on the island's west coast extended north to Cape Scott and across the Queen Charlotte Strait to the Broughton Archipelago and south to Clayoquot Sound and Tofino. In 1989, a separate colony was discovered in the central British Columbia coast. It is not known if this colony, which numbered about 300 animals in 2004, was founded by transplanted otters or was a remnant population that had gone undetected. By 2013, this population exceeded 1,100 individuals, was increasing at an estimated 12.6% annual rate, and its range included Aristazabal Island, and Milbanke Sound south to Calvert Island. In 2008, Canada determined the status of sea otters to be "special concern".
United States | Sea otter | Wikipedia | 457 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Alaska
Alaska is the central area of the sea otter's range. In 1973, the population in Alaska was estimated at between 100,000 and 125,000 animals. By 2006, though, the Alaska population had fallen to an estimated 73,000 animals. A massive decline in sea otter populations in the Aleutian Islands accounts for most of the change; the cause of this decline is not known, although orca predation is suspected. The sea otter population in Prince William Sound was also hit hard by the Exxon Valdez oil spill, which killed thousands of sea otters in 1989.
Washington
In 1969 and 1970, 59 sea otters were translocated from Amchitka Island to Washington, and released near La Push and Point Grenville. The translocated population is estimated to have declined to between 10 and 43 individuals before increasing, reaching 208 individuals in 1989. As of 2017, the population was estimated at over 2,000 individuals, and their range extends from Point Grenville in the south to Cape Flattery in the north and east to Pillar Point along the Strait of Juan de Fuca.
In Washington, sea otters are found almost exclusively on the outer coasts. They can swim as close as six feet off shore along the Olympic coast. Reported sightings of sea otters in the San Juan Islands and Puget Sound almost always turn out to be North American river otters, which are commonly seen along the seashore. However, biologists have confirmed isolated sightings of sea otters in these areas since the mid-1990s.
Oregon
The last native sea otter in Oregon was probably shot and killed in 1906. In 1970 and 1971, a total of 95 sea otters were transplanted from Amchitka Island, Alaska to the Southern Oregon coast. However, this translocation effort failed and otters soon again disappeared from the state. In 2004, a male sea otter took up residence at Simpson Reef off of Cape Arago for six months. This male is thought to have originated from a colony in Washington, but disappeared after a coastal storm. On 18 February 2009, a male sea otter was spotted in Depoe Bay off the Oregon Coast. It could have traveled to the state from either California or Washington.
California | Sea otter | Wikipedia | 453 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
The historic population of California sea otters was estimated at 16,000 before the fur trade decimated the population, leading to their assumed extinction. Today's population of California sea otters are the descendants of a single colony of about 50 sea otters located near Bixby Creek Bridge in March 1938. Their principal range has gradually expanded and extends from Pigeon Point in San Mateo County to Santa Barbara County.
Sea otters were once numerous in San Francisco Bay. Historical records revealed the Russian-American Company snuck Aleuts into San Francisco Bay multiple times, despite the Spanish capturing or shooting them while hunting sea otters in the estuaries of San Jose, San Mateo, San Bruno and around Angel Island. The founder of Fort Ross, Ivan Kuskov, finding otters scarce on his second voyage to Bodega Bay in 1812, sent a party of Aleuts to San Francisco Bay, where they met another Russian party and an American party, and caught 1,160 sea otters in three months. By 1817, sea otters in the area were practically eliminated and the Russians sought permission from the Spanish and the Mexican governments to hunt further and further south of San Francisco. In 1833, fur trappers George Nidever and George Yount canoed "along the Petaluma side of [the] Bay, and then proceeded to the San Joaquin River", returning with sea otter, beaver, and river otter pelts. Remnant sea otter populations may have survived in the bay until 1840, when the Rancho Punta de Quentin was granted to Captain John B. R. Cooper, a sea captain from Boston, by Mexican Governor Juan Bautista Alvarado along with a license to hunt sea otters, reportedly then prevalent at the mouth of Corte Madera Creek. | Sea otter | Wikipedia | 355 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
In the late 1980s, the USFWS relocated about 140 southern sea otters to San Nicolas Island in southern California, in the hope of establishing a reserve population should the mainland be struck by an oil spill. To the surprise of biologists, the majority of the San Nicolas sea otters swam back to the mainland. Another group of twenty swam north to San Miguel Island, where they were captured and removed. By 2005, only 30 sea otters remained at San Nicolas, although they were slowly increasing as they thrived on the abundant prey around the island. The plan that authorized the translocation program had predicted the carrying capacity would be reached within five to 10 years. The spring 2016 count at San Nicolas Island was 104 sea otters, continuing a 5-year positive trend of over 12% per year. Sea otters were observed twice in Southern California in 2011, once near Laguna Beach and once at Zuniga Point Jetty, near San Diego. These are the first documented sightings of otters this far south in 30 years. | Sea otter | Wikipedia | 210 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
When the USFWS implemented the translocation program, it also attempted, in 1986, to implement "zonal management" of the Californian population. To manage the competition between sea otters and fisheries, it declared an "otter-free zone" stretching from Point Conception to the Mexican border. In this zone, only San Nicolas Island was designated as sea otter habitat, and sea otters found elsewhere in the area were supposed to be captured and relocated. These plans were abandoned after many translocated otters died and also as it proved impractical to capture the hundreds of otters which ignored regulations and swam into the zone. However, after engaging in a period of public commentary in 2005, the Fish and Wildlife Service failed to release a formal decision on the issue. Then, in response to lawsuits filed by the Santa Barbara-based Environmental Defense Center and the Otter Project, on 19 December 2012 the USFWS declared that the "no otter zone" experiment was a failure, and will protect the otters re-colonizing the coast south of Point Conception as threatened species. Although abalone fisherman blamed the incursions of sea otters for the decline of abalone, commercial abalone fishing in southern California came to an end from overfishing in 1997, years before significant otter moved south of Point Conception. In addition, white abalone (Haliotis sorenseni), a species never overlapping with sea otter, had declined in numbers 99% by 1996, and became the first marine invertebrate to be federally listed as endangered. | Sea otter | Wikipedia | 315 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Although the southern sea otter's range has continuously expanded from the remnant population of about 50 individuals in Big Sur since protection in 1911, from 2007 to 2010, the otter population and its range contracted and since 2010 has made little progress. As of spring 2010, the northern boundary had moved from about Tunitas Creek to a point southeast of Pigeon Point, and the southern boundary has moved along the Gaviota Coast from approximately Coal Oil Point to Gaviota State Park. A toxin called microcystin, produced by a type of cyanobacteria (Microcystis), seems to be concentrated in the shellfish the otters eat, poisoning them. Cyanobacteria are found in stagnant water enriched with nitrogen and phosphorus from septic tank and agricultural fertilizer runoff, and may be flushed into the ocean when streamflows are high in the rainy season. A record number of sea otter carcasses were found on California's coastline in 2010, with increased shark attacks an increasing component of the mortality. Great white sharks do not consume relatively fat-poor sea otters but shark-bitten carcasses have increased from 8% in the 1980s to 15% in the 1990s and to 30% in 2010 and 2011. | Sea otter | Wikipedia | 253 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
For southern sea otters to be considered for removal from threatened species listing, the U.S. Fish and Wildlife Service (USFWS) determined that the population should exceed 3,090 for three consecutive years. In response to recovery efforts, the population climbed steadily from the mid-20th century through the early 2000s, then remained relatively flat from 2005 to 2014 at just under 3,000. There was some contraction from the northern (now Pigeon Point) and southern limits of the sea otter's range during the end of this period, circumstantially related to an increase in lethal shark bites, raising concerns that the population had reached a plateau. However, the population increased markedly from 2015 to 2016, with the United States Geological Survey (USGS) California sea otter survey 3-year average reaching 3,272 in 2016, the first time it exceeded the threshold for delisting from the Endangered Species Act (ESA). If populations continued to grow and ESA delisting occurred, southern sea otters would still be fully protected by state regulations and the Marine Mammal Protection Act, which set higher thresholds for protection, at approximately 8,400 individuals. However, ESA delisting seems unlikely due to a precipitous population decline recorded in the spring 2017 USGS sea otter survey count, from the 2016 high of 3,615 individuals to 2,688, a loss of 25% of the California sea otter population. | Sea otter | Wikipedia | 293 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Mexico
Historian Adele Ogden described sea otters as being particularly abundant in "Lower California", now the Baja California Peninsula, where "seven bays...were main centers". The southernmost limit was Punta Morro Hermoso about south of Punta Eugenia, in turn a headland at the southwestern end of Sebastián Vizcaíno Bay, on the west coast of the Baja Peninsula. Otter were also taken from San Benito Island, Cedros Island, and Isla Natividad in the Bay. By the early 1900s, Baja's sea otters were extirpated by hunting. In a 1997 survey, small numbers of sea otters, including pups, were reported by local fishermen, but scientists could not confirm these accounts. However, male and female otters have been confirmed by scientists off shores of the Baja Peninsula in a 2014 study, who hypothesize that otter dispersed there beginning in 2005. These sea otters may have dispersed from San Nicolas Island, which is away, as individuals have been recorded traversing distances of over . Genetic analysis of most of these animals were consistent with California, i.e. United States, otter origins, however one otter had a haplotype not previously reported, and could represent a remnant of the original native Mexican otter population.
Ecology
Diet
High energetic requirements of sea otter metabolism require them to consume at least 20% of their body weight a day. Surface swimming and foraging are major factors in their high energy expenditure due to drag on the surface of the water when swimming and the thermal heat loss from the body during deep dives when foraging. Sea otter muscles are specially adapted to generate heat without physical activity. | Sea otter | Wikipedia | 336 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Sea otters are apex predators that consume over 100 prey species. In most of its range, the sea otter's diet consists almost exclusively of marine benthic invertebrates, including sea urchins (such as Strongylocentrotus franciscanus and S. purpuratus), sea cucumbers, fat innkeeper worms, crustaceans, a variety of mollusks such as chitons (such as Katharina tunicata), snails such as abalones and limpets (such as Diodora aspera), and bivalves such as clams, mussels (such as Mytilus edulis), and scallops (such as Crassadoma gigantea). Its prey ranges in size from tiny limpets and crabs to giant octopuses. Where prey such as sea urchins, clams, and abalone are present in a range of sizes, sea otters tend to select larger items over smaller ones of similar type. In California, they have been noted to ignore Pismo clams smaller than across.
In a few northern areas, fish are also eaten. In studies performed at Amchitka Island in the 1960s, where the sea otter population was at carrying capacity, 50% of food found in sea otter stomachs was fish. The fish species were usually bottom-dwelling and sedentary or sluggish forms, such as Hemilepidotus hemilepidotus and family Tetraodontidae. However, south of Alaska on the North American coast, fish are a negligible or extremely minor part of the sea otter's diet. Contrary to popular depictions, sea otters rarely eat starfish, and any kelp that is consumed apparently passes through the sea otter's system undigested. Sea otters will also occasionally prey on seabirds. In California, the most commonly eaten species were western grebes, although cormorants, gulls, common loons, and surf scoters were also consumed. | Sea otter | Wikipedia | 415 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
The individuals within a particular area often differ in their foraging methods and prey types, and tend to follow the same patterns as their mothers. The diet of local populations also changes over time, as sea otters can significantly deplete populations of highly preferred prey such as large sea urchins, and prey availability is also affected by other factors such as fishing by humans. Sea otters can thoroughly remove abalone from an area except for specimens in deep rock crevices, however, they never completely wipe out a prey species from an area. A 2007 Californian study demonstrated, in areas where food was relatively scarce, a wider variety of prey was consumed. Surprisingly, though, the diets of individuals were more specialized in these areas than in areas where food was plentiful.
As a keystone species
Sea otters are a classic example of a keystone species; their presence affects the ecosystem more profoundly than their size and numbers would suggest. They keep the population of certain benthic (sea floor) herbivores, particularly sea urchins, in check. Sea urchins graze on the lower stems of kelp, causing the kelp to drift away and die. Loss of the habitat and nutrients provided by kelp forests leads to profound cascade effects on the marine ecosystem. North Pacific areas that do not have sea otters often turn into urchin barrens, with abundant sea urchins and no kelp forest. Kelp forests are extremely productive ecosystems. Kelp forests sequester (absorb and capture) CO2 from the atmosphere through photosynthesis. Sea otters may help mitigate effects of climate change by their cascading trophic influence.
Reintroduction of sea otters to British Columbia has led to a dramatic improvement in the health of coastal ecosystems, and similar changes have been observed as sea otter populations recovered in the Aleutian and Commander Islands and the Big Sur coast of California. However, some kelp forest ecosystems in California have also thrived without sea otters, with sea urchin populations apparently controlled by other factors. The role of sea otters in maintaining kelp forests has been observed to be more important in areas of open coast than in more protected bays and estuaries.
Sea otters affect rocky ecosystems that are dominated by mussel beds by removing mussels from rocks. This allows space for competing species and increases species diversity. | Sea otter | Wikipedia | 481 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Predators
The leading mammalian predators of this species is the orca. Sea lions and bald eagles may prey on pups. On land, young sea otters may face attack from bears and coyotes. In California, great white sharks are their primary predator, though this is the result of mistaking otters for seals and they do not consume otters after biting them. In Katmai National Park, grey wolves have been recorded to hunt and kill sea otters.
Urban runoff transporting cat feces into the ocean brings Toxoplasma gondii, an obligate parasite of felids, which has killed sea otters. Parasitic infections of Sarcocystis neurona are also associated with human activity. According to the U.S. Geological Survey and the CDC, northern sea otters off Washington have been infected with the H1N1 flu virus and "may be a newly identified animal host of influenza viruses".
Relationship with humans
Fur trade
Sea otters have the thickest fur of any mammal, which makes them a common target for many hunters. Archaeological evidence indicates that for thousands of years, indigenous peoples have hunted sea otters for food and fur. Large-scale hunting, part of the Maritime Fur Trade, which would eventually kill approximately one million sea otters, began in the 18th century when hunters and traders began to arrive from all over the world to meet foreign demand for otter pelts, which were one of the world's most valuable types of fur. | Sea otter | Wikipedia | 301 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
In the early 18th century, Russians began to hunt sea otters in the Kuril Islands and sold them to the Chinese at Kyakhta. Russia was also exploring the far northern Pacific at this time, and sent Vitus Bering to map the Arctic coast and find routes from Siberia to North America. In 1741, on his second North Pacific voyage, Bering was shipwrecked off Bering Island in the Commander Islands, where he and many of his crew died. The surviving crew members, which included naturalist Georg Steller, discovered sea otters on the beaches of the island and spent the winter hunting sea otters and gambling with otter pelts. They returned to Siberia, having killed nearly 1,000 sea otters, and were able to command high prices for the pelts. Thus began what is sometimes called the "Great Hunt", which would continue for another hundred years. The Russians found the sea otter far more valuable than the sable skins that had driven and paid for most of their expansion across Siberia. If the sea otter pelts brought back by Bering's survivors had been sold at Kyakhta prices they would have paid for one tenth the cost of Bering's expedition.
Russian fur-hunting expeditions soon depleted the sea otter populations in the Commander Islands, and by 1745, they began to move on to the Aleutian Islands. The Russians initially traded with the Aleuts inhabitants of these islands for otter pelts, but later enslaved the Aleuts, taking women and children hostage and torturing and killing Aleut men to force them to hunt. Many Aleuts were either murdered by the Russians or died from diseases the hunters had introduced. The Aleut population was reduced, by the Russians' own estimate, from 20,000 to 2,000. By the 1760s, the Russians had reached Alaska. In 1799, Tsar Paul I consolidated the rival fur-hunting companies into the Russian-American Company, granting it an imperial charter and protection, and a monopoly over trade rights and territorial acquisition.
Under Aleksander I, the administration of the merchant-controlled company was transferred to the Imperial Navy, largely due to the alarming reports by naval officers of native abuse; in 1818, the indigenous peoples of Alaska were granted civil rights equivalent to a townsman status in the Russian Empire. | Sea otter | Wikipedia | 467 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Other nations joined in the hunt in the south. Along the coasts of what is now Mexico and California, Spanish explorers bought sea otter pelts from Native Americans and sold them in Asia. In 1778, British explorer Captain James Cook reached Vancouver Island and bought sea otter furs from the First Nations people. When Cook's ship later stopped at a Chinese port, the pelts rapidly sold at high prices, and were soon known as "soft gold". As word spread, people from all over Europe and North America began to arrive in the Pacific Northwest to trade for sea otter furs.
Russian hunting expanded to the south, initiated by American ship captains, who subcontracted Russian supervisors and Aleut hunters in what are now Washington, Oregon, and California. Between 1803 and 1846, 72 American ships were involved in the otter hunt in California, harvesting an estimated 40,000 skins and tails, compared to only 13 ships of the Russian-American Company, which reported 5,696 otter skins taken between 1806 and 1846. In 1812, the Russians founded an agricultural settlement at what is now Fort Ross in northern California, as their southern headquarters.
Eventually, sea otter populations became so depleted, commercial hunting was no longer viable. It had stopped in the Aleutian Islands, by 1808, as a conservation measure imposed by the Russian-American Company. Further restrictions were ordered by the company in 1834. When Russia sold Alaska to the United States in 1867, the Alaska population had recovered to over 100,000, but Americans resumed hunting and quickly extirpated the sea otter again. Prices rose as the species became rare. During the 1880s, a pelt brought $105 to $165 in the London market, but by 1903, a pelt could be worth as much as $1,125. In 1911, Russia, Japan, Great Britain (for Canada) and the United States signed the Treaty for the Preservation and Protection of Fur Seals, imposing a moratorium on the harvesting of sea otters. So few remained, perhaps only 1,000–2,000 individuals in the wild, that many believed the species would become extinct.
Recovery and conservation | Sea otter | Wikipedia | 432 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
During the 20th century, sea otter numbers rebounded in about two-thirds of their historic range, a recovery considered one of the greatest successes in marine conservation. However, the IUCN still lists the sea otter as an endangered species, and describes the significant threats to sea otters as oil pollution, predation by orcas, poaching, and conflicts with fisheries – sea otters can drown if entangled in fishing gear. The hunting of sea otters is no longer legal except for limited harvests by indigenous peoples in the United States. Poaching was a serious concern in the Russian Far East immediately after the collapse of the Soviet Union in 1991; however, it has declined significantly with stricter law enforcement and better economic conditions.
The most significant threat to sea otters is oil spills, to which they are particularly vulnerable, since they rely on their fur to keep warm. When their fur is soaked with oil, it loses its ability to retain air, and the animals can quickly die from hypothermia. The liver, kidneys, and lungs of sea otters also become damaged after they inhale oil or ingest it when grooming. The Exxon Valdez oil spill of 24 March 1989 killed thousands of sea otters in Prince William Sound, and as of 2006, the lingering oil in the area continues to affect the population. Describing the public sympathy for sea otters that developed from media coverage of the event, a U.S. Fish and Wildlife Service spokesperson wrote: | Sea otter | Wikipedia | 303 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
The small geographic ranges of the sea otter populations in California, Washington, and British Columbia mean a single major spill could be catastrophic for that state or province. Prevention of oil spills and preparation to rescue otters if one happens is a major focus for conservation efforts. Increasing the size and range of sea otter populations would also reduce the risk of an oil spill wiping out a population. However, because of the species' reputation for depleting shellfish resources, advocates for commercial, recreational, and subsistence shellfish harvesting have often opposed allowing the sea otter's range to increase, and there have even been instances of fishermen and others illegally killing them.
With a population size of fifty, the low genetic diversity amongst the population post-fur trade but pre-discovery produced an evolutionary bottleneck. The recent population constraints put on the sea otter have led to low genomic diversity among species members, with much evidence of inbreeding. This inbreeding has led to the mutation of deleterious missense mutations, which may make fast-paced population growth difficult for conservation reasons. While longer-term recovery goals bolstering genetic diversity by inbreeding are costly and challenging, they could significantly aid in avoiding the further evolution of deleterious variation, thus aiding sea otter population stabilization. This method has already been utilized in returning cheetah populations to higher numbers and higher genetic diversity, and captive breeding programs through organizations such as the Monterey Bay Aquarium and The Marine Mammal Center make the chances of getting sea otter populations back up to pre-fur trade numbers possible. The population of sea otters in California has risen to around 3,000 in the wild. While this figure is far below pre-fur trade numbers, it represents a massive improvement in the conservation of the species and a massive increase in genetic diversity. On the other hand, northern sea otters have reached back up to pre-fur trade population numbers, with populations living all along the state's coast from Ketchikan in the south to Attu in the west. Historical populations, however, are estimated to have been between 150,000 and 300,000 individuals living along the northern Pacific rim from Baja California to Hokkaido Island in Japan. Modern conservation techniques have included breeding northern and southern populations of sea otters to increase genetic diversity and prevent both inbreeding and genetic drift. Moreover, the introduction of the Marine Mammal Protection Act in the 1970s made their hunting highly illegal in the United States. | Sea otter | Wikipedia | 494 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
In the Aleutian Islands, a massive and unexpected disappearance of sea otters has occurred in recent decades. In the 1980s, the area was home to an estimated 55,000 to 100,000 sea otters, but the population fell to around 6,000 animals by 2000. The most widely accepted, but still controversial, hypothesis is that killer whales have been eating the otters. The pattern of disappearances is consistent with a rise in predation, but there has been no direct evidence of orcas preying on sea otters to any significant extent.
Another area of concern is California, where recovery began to fluctuate or decline in the late 1990s. Unusually high mortality rates amongst adult and subadult otters, particularly females, have been reported. In 2017 the US Geological Survey found a 3% drop in the sea otter population of the California coast. This number still keeps them on track for removal from the endangered species list, although just barely. Necropsies of dead sea otters indicate diseases, particularly Toxoplasma gondii and acanthocephalan parasite infections, are major causes of sea otter mortality in California. The Toxoplasma gondii parasite, which is often fatal to sea otters, is carried by wild and domestic cats and may be transmitted by domestic cat droppings flushed into the ocean via sewage systems. Although disease has clearly contributed to the deaths of many of California's sea otters, it is not known why the California population is apparently more affected by disease than populations in other areas.
Sea otter habitat is preserved through several protected areas in the United States, Russia and Canada. In marine protected areas, polluting activities such as dumping of waste and oil drilling are typically prohibited. An estimated 1,200 sea otters live within the Monterey Bay National Marine Sanctuary, and more than 500 live within the Olympic Coast National Marine Sanctuary.
Economic impact
Some of the sea otter's preferred prey species, particularly abalone, clams, and crabs, are also food sources for humans. In some areas, massive declines in shellfish harvests have been blamed on the sea otter, and intense public debate has taken place over how to manage the competition between sea otters and humans for seafood. | Sea otter | Wikipedia | 455 | 567471 | https://en.wikipedia.org/wiki/Sea%20otter | Biology and health sciences | Carnivora | null |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.