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Air forces have long recognized the strategic importance of liquid oxygen, both as an oxidizer and as a supply of gaseous oxygen for breathing in hospitals and high-altitude aircraft flights. In 1985, the USAF started a program of building its own oxygen-generation facilities at all major consumption bases.
In rocket propellant
Liquid oxygen is the most common cryogenic liquid oxidizer propellant for spacecraft rocket applications, usually in combination with liquid hydrogen, kerosene or methane.
Liquid oxygen was used in the first liquid fueled rocket. The World War II V-2 missile also used liquid oxygen under the name A-Stoff and Sauerstoff. In the 1950s, during the Cold War both the United States' Redstone and Atlas rockets, and the Soviet R-7 Semyorka used liquid oxygen. Later, in the 1960s and 1970s, the ascent stages of the Apollo Saturn rockets, and the Space Shuttle main engines used liquid oxygen.
As of 2024, many active rockets use liquid oxygen:
Chinese space program
CASC: Long March 5, Long March 6, Long March 7, Long March 8, Long March 12, Long March 9 (under development), Long March 10 (under development)
Galactic Energy: Pallas-1 (under development)
i-Space: Hyperbola-3 (under development)
LandSpace: Zhuque-2
Orienspace: Gravity-2 (under development)
Space Pioneer: Tianlong-2
European Space Agency: Ariane 6
Indian Space Research Organisation: GSLV
JAXA (Japan): H-IIA, H3
Korea Aerospace Research Institute: Naro-1, Nuri
Roscosmos (Russia): Soyuz-2, Angara
United States
Blue Origin: New Shepard, New Glenn (under development)
Firefly Aerospace: Firefly Alpha
NASA: Space Launch System
Northrop Grumman: Antares 300 (under development)
Rocket Lab: Electron, Neutron (under development)
SpaceX: Falcon 9, Falcon Heavy, Starship
United Launch Alliance: Atlas V, Vulcan | Liquid oxygen | Wikipedia | 414 | 314402 | https://en.wikipedia.org/wiki/Liquid%20oxygen | Physical sciences | Group 16 | Chemistry |
History
By 1845, Michael Faraday had managed to liquefy most gases then known to exist. Six gases, however, resisted every attempt at liquefaction and were known at the time as "permanent gases". They were oxygen, hydrogen, nitrogen, carbon monoxide, methane, and nitric oxide.
In 1877, Louis Paul Cailletet in France and Raoul Pictet in Switzerland succeeded in producing the first droplets of liquid air.
In 1883, Polish professors Zygmunt Wróblewski and Karol Olszewski produced the first measurable quantity of liquid oxygen. | Liquid oxygen | Wikipedia | 120 | 314402 | https://en.wikipedia.org/wiki/Liquid%20oxygen | Physical sciences | Group 16 | Chemistry |
In lunar astronomy, libration is the cyclic variation in the apparent position of the Moon that is perceived by observers on the Earth observers and caused by changes between the orbital and rotational planes of the moon. It causes an observer to see slightly different hemispheres of the surface at different times. It is similar in both cause and effect to the changes in the Moon's apparent size because of changes in distance. It is caused by three mechanisms detailed below, two of which cause a relatively tiny physical libration via tidal forces exerted by the Earth. Such true librations are known as well for other moons with locked rotation.
The quite different phenomenon of a trojan asteroid's movement has been called Trojan libration, and Trojan libration point means Lagrangian point.
Lunar libration
The Moon keeps one hemisphere of itself facing the Earth because of tidal locking. Therefore, the first view of the far side of the Moon was not possible until the Soviet probe Luna 3 reached the Moon on October 7, 1959, and further lunar exploration by the United States and the Soviet Union. This simple picture is only approximately true since over time, slightly more than half (about 59% in total) of the Moon's surface is seen from Earth because of libration.
Lunar libration arises from three changes in perspective because of the non-circular and inclined orbit, the finite size of the Earth, and the orientation of the Moon in space. The first of these is called optical libration, the second parallax, and the third physical libration. Each of these can be divided into two contributions. | Libration | Wikipedia | 330 | 314494 | https://en.wikipedia.org/wiki/Libration | Physical sciences | Celestial mechanics | Astronomy |
The following are the three types of lunar libration:
Optical libration, the combined libration of longitudinal and latitudinal libration produces a movement of the sub-Earth point and a wobbling view between the temporarily visible parts of the Moon, during a lunar orbit. This is not to be confused with the change of the Moon's apparent size because of the changing distance between the Moon and the Earth during the Moon's elliptic orbit, or with the change of positional angle because of the change in the position of the Moon's tilted axis, or with the observed swinging motion of the Moon because of the relative position of the Earth's tilted axis during an orbit of the Moon.
Libration in longitude results from the eccentricity of the orbit of the Moon around the Earth; the Moon's rotation sometimes leads and sometimes lags its orbital position. The lunar libration in longitude was discovered by Johannes Hevelius in 1648. It can reach 7°54′ in amplitude. Longitudinal libration allows an observer on Earth to view at times further into the Moon's west and east respectively at different phases of the Moon's orbit.
Libration in latitude results from the Moon's axial tilt (about 6.7°) between its rotation axis and orbital axis around Earth. This is analogous to how Earth's seasons arise from its axial tilt (about 23.4°) between its rotation axis and orbital axis about the Sun. Galileo Galilei is sometimes credited with the discovery of the lunar libration in latitude in 1632 although Thomas Harriot or William Gilbert might have done so before. Note Cassini's laws. It can reach 6°50′ in amplitude. The 6.7° depends on the orbit inclination of 5.15° and the negative equatorial tilt of 1.54°. Latitudinal libration allows an observer on Earth to view beyond the Moon's north pole and south pole at different phases of the Moon's orbit.
Parallax libration depends on both the longitude and latitude of the location on Earth from which the Moon is observed. | Libration | Wikipedia | 441 | 314494 | https://en.wikipedia.org/wiki/Libration | Physical sciences | Celestial mechanics | Astronomy |
Diurnal libration is the small daily libration and oscillation from Earth's rotation, which carries an observer first to one side and then to the other side of the straight line joining Earth's and the Moon's centers, allowing the observer to look first around one side of the Moon and then around the other—since the observer is on Earth's surface, not at its center. It reaches less than 1° in amplitude.
Physical libration is the oscillation of orientation in space about uniform rotation and precession. There are physical librations about all three axes. The sizes are roughly 100 seconds of arc. As seen from the Earth, this amounts to less than 1 second of arc. Forced physical librations can be predicted given the orbit and shape of the Moon. The periods of free physical librations can also be predicted, but their amplitudes and phases cannot be predicted. | Libration | Wikipedia | 191 | 314494 | https://en.wikipedia.org/wiki/Libration | Physical sciences | Celestial mechanics | Astronomy |
Physical libration
Also called real libration, as opposed to the optical libration of longitudinal, latitudinal and diurnal types, the orientation of the Moon exhibits small oscillations of the pole direction in space and rotation about the pole.
This libration can be differentiated between forced and free libration. Forced libration is caused by the forces exerted during the Moon's orbit around the Earth and the Sun, and free libration represents oscillations that occur over longer time periods.
Forced physical libration
Cassini's laws state the following:
The Moon rotates uniformly about its polar axis keeping one side toward the Earth.
The Moon's equator plane is tilted with respect to the ecliptic plane and it precesses uniformly along the ecliptic plane.
The descending node of the equator on the ecliptic matches the ascending node of the orbit plane.
In addition to uniform rotation and uniform precession of the equator plane, the Moon has small oscillations of orientation in space about all three axes. These oscillations are called physical librations. Apart from the 1.5427° tilt between equator and ecliptic, the oscillations are approximately ±100 seconds of arc in size. These oscillations can be expressed with trigonometric series that depend on the lunar moments of inertia A < B < C. The sensitive combinations are β = (C – A)/B and γ = (B – A)/C. The oscillation about the polar axis is most sensitive to γ and the 2-dimensional direction of the pole, including the 1.5427° tilt, is most sensitive to β. Consequently, accurate measurements of the physical librations provide accurate determinations of β = and γ = .
The placement of three retroreflectors on the Moon by the Lunar Laser Ranging experiment and two retroreflectors by Lunokhod rovers allowed accurate measurement of the physical librations by laser ranging to the Moon. | Libration | Wikipedia | 423 | 314494 | https://en.wikipedia.org/wiki/Libration | Physical sciences | Celestial mechanics | Astronomy |
Free physical libration
A free physical libration is similar to the solution of the reduced equation for linear differential equations. The periods of the free librations can be calculated, but their amplitudes must be measured. Lunar Laser Ranging provides the determinations. The two largest free librations were discovered by O. Calame. Modern values are:
1.3 seconds of arc with a 1056-day (2.9-year) period for rotation about the polar axis,
a 74.6-year elliptical wobble of the pole of size 8.18 × 3.31 arcseconds, and
an 81-year rotation of the pole in space that is 0.03 seconds of arc in size.
The fluid core can cause a fourth mode with a period around four centuries. The free librations are expected to damp out in times very short compared to the age of the Moon. Consequently, their existence implies that there must be one or more stimulating mechanisms. | Libration | Wikipedia | 199 | 314494 | https://en.wikipedia.org/wiki/Libration | Physical sciences | Celestial mechanics | Astronomy |
The dire wolf (Aenocyon dirus ) is an extinct canine. The dire wolf lived in the Americas during the Late Pleistocene and Early Holocene epochs (125,000–9,500 years ago). A putative, controversial fossil was recently reported from northeast China, but other researchers questioned the taxonomic attribution of this specimen. The species was named in 1858, four years after the first specimen had been found. Two subspecies are recognized: Aenocyon dirus guildayi and Aenocyon dirus dirus. The largest collection of its fossils has been obtained from the Rancho La Brea Tar Pits in Los Angeles.
Dire wolf remains have been found across a broad range of habitats including the plains, grasslands, and some forested mountain areas of North America and the arid savanna of South America. The sites range in elevation from sea level to . Dire wolf fossils have rarely been found north of 42°N latitude; there have been only five unconfirmed reports above this latitude. This range restriction is thought to be due to temperature, prey, or habitat limitations imposed by proximity to the Laurentide and Cordilleran ice sheets that existed at the time.
The dire wolf was about the same size as the largest modern gray wolves (Canis lupus): the Yukon wolf and the northwestern wolf. A.d.guildayi weighed on average and A.d.dirus was on average . Its skull and dentition matched those of C.lupus, but its teeth were larger with greater shearing ability, and its bite force at the canine tooth was stronger than any known Canis species. These characteristics are thought to be adaptations for preying on Late Pleistocene megaherbivores, and in North America, its prey is known to have included western horses, ground sloths, mastodons, ancient bison, and camels. Its extinction occurred during the Quaternary extinction event along with its main prey species. Its reliance on megaherbivores has been proposed as the cause of its extinction, along with climatic change and competition with other species, or a combination of those factors. Dire wolves lived as recently as 9,500 years ago, according to dated remains.
Taxonomy | Dire wolf | Wikipedia | 450 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
From the 1850s, the fossil remains of extinct large wolves were being found in the United States, and it was not immediately clear that these all belonged to one species. The first specimen of what would later become associated with Aenocyon dirus was found in mid-1854 in the bed of the Ohio River near Evansville, Indiana. The fossilized jawbone with cheek teeth was obtained by the geologist Joseph Granville Norwood from an Evansville collector, Francis A. Linck. The paleontologist Joseph Leidy determined that the specimen represented an extinct species of wolf and reported it under the name of Canis primaevus. Norwood's letters to Leidy are preserved along with the type specimen (the first of a species that has a written description) at the Academy of Natural Sciences of Philadelphia. In 1857, while exploring the Niobrara River valley in Nebraska, Leidy found the vertebrae of an extinct Canis species that he reported the following year under the name C.dirus. The name C.primaevus (Leidy 1854) was later renamed Canis indianensis (Leidy 1869) when Leidy found out that the name C.primaevus had previously been used by the British naturalist Brian Houghton Hodgson for the dhole. | Dire wolf | Wikipedia | 254 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
In 1876 the zoologist Joel Asaph Allen discovered the remains of Canis mississippiensis (Allen 1876) and associated these with C.dirus (Leidy 1858) and Canis indianensis (Leidy 1869). As so little was found of these three specimens, Allen thought it best to leave each specimen listed under its provisional name until more material could be found to reveal their relationship. In 1908 the paleontologist John Campbell Merriam began retrieving numerous fossilized bone fragments of a large wolf from the Rancho LaBrea tar pits. By 1912 he had found a skeleton sufficiently complete to be able to formally recognize these and the previously found specimens under the name C.dirus (Leidy 1858). Because the rules of nomenclature stipulated that the name of a species should be the oldest name ever applied to it, Merriam therefore selected the name of Leidy's 1858 specimen, C.dirus. In 1915 the paleontologist Edward Troxell indicated his agreement with Merriam when he declared C.indianensis a synonym of C.dirus. In 1918, after studying these fossils, Merriam proposed consolidating their names under the separate genus Aenocyon (from ainos, 'terrible' and cyon, 'dog') to become Aenocyon dirus, but at that time not everyone agreed with this extinct wolf being placed in a new genus separate from the genus Canis. Canis ayersi (Sellards 1916) and Aenocyon dirus (Merriam 1918) were recognized as synonyms of C.dirus by the paleontologist Ernest Lundelius in 1972. All of the above taxa were declared synonyms of C.dirus in 1979, according to the paleontologist Ronald M. Nowak.
In 1984 a study by Björn Kurtén recognized a geographic variation within the dire wolf populations and proposed two subspecies: Canis dirus guildayi (named by Kurtén in honor of the paleontologist John E. Guilday) for specimens from California and Mexico that exhibited shorter limbs and longer teeth, and Canis dirus dirus for specimens east of the North American Continental Divide that exhibited longer limbs and shorter teeth. Kurtén designated a maxilla found in Hermit's Cave, New Mexico as representing the nominate subspecies C. d. dirus. | Dire wolf | Wikipedia | 475 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
In 2021, a DNA study found the dire wolf to be a highly divergent lineage when compared with the extant wolf-like canines, and this finding is consistent with the previously proposed taxonomic classification of the dire wolf as genus Aenocyon (Ancient Greek: "terrible wolf") as proposed by Merriam in 1918.
Evolution
In North America, the canid family came into existence 40 million years ago, and the canine subfamily Caninae about 32 million years ago. From the Caninae, the ancestors of the fox-like Vulpini and the dog-like Canini came into existence 9 million years ago. This group was first represented by Eucyon, and mostly by coyote-like Eucyon davisi that was spread widely across North America. From the Canini the Cerdocyonina, today represented by the South American canids, came into existence 6–5 million years ago. Its sister the wolf-like Canina came into existence 5 million years ago, however, they are likely to have originated as far back as 9 million years ago. Around 7 million years ago, the canines expanded into Eurasia and Africa, with Eucyon giving rise to the first of the genus Canis in Europe. Around 4–3 million years ago C. chihliensis, the first wolf-sized member of Canis, arose in China and expanded to give rise to other wolf-like members across Eurasia and Africa. Members of the genus Canis would later expand into North America.
The dire wolf evolved in North America. However, its ancestral lineage is debated, with two competing theories. The first theory is based on fossil morphology, which indicates that an expansion of the genus Canis out of Eurasia led to the dire wolf. The second theory is based on DNA evidence, which indicates that the dire wolf arose from an ancestral lineage that originated in the Americas and was separate from the genus Canis.
Morphological evidence
Morphological evidence based on fossil remains indicates an expansion of genus Canis from out of Eurasia led to the dire wolf. | Dire wolf | Wikipedia | 416 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
In 1974 Robert A. Martin proposed that the large North American wolf C. armbrusteri (Armbruster's wolf) was C. lupus. Nowak, Kurtén, and Annalisa Berta proposed that C. dirus was not derived from C. lupus. In 1987, a new hypothesis proposed that a mammal population could give rise to a larger form called a hypermorph during times when food was abundant, but when food later became scarce the hypermorph would either adapt to a smaller form or go extinct. This hypothesis might explain the large body sizes found in many Late Pleistocene mammals compared to their modern counterparts. Both extinction and speciationa process by which a new species splits from an older onecould occur together during periods of climatic extremes. Gloria D. Goulet agreed with Martin, proposing further that this hypothesis might explain the sudden appearance of C. dirus in North America and, judging from the similarities in their skull shapes, that C. lupus had given rise to the C. dirus hypermorph due to an abundance of game, a stable environment, and large competitors.
The three paleontologists Xiaoming Wang, Richard H. Tedford, and Ronald M. Nowak propose that C. dirus evolved from Canis armbrusteri, with Nowak stating that both species arose in the Americas and that specimens found in Cumberland Cave, Maryland, appear to be C. armbrusteri diverging into C. dirus. Nowak believed that Canis edwardii was the first appearance of the wolf in North America, and it appears to be close to the lineage which produced C. armbrusteri and C. dirus. Tedford believes that the early wolf from China, Canis chihliensis, may have been the ancestor of both C. armbrusteri and the gray wolf C. lupus. The sudden appearance of C. armbrusteri in mid-latitude North America during the Early Pleistocene 1.5 million years ago, along with the mammoth, suggests that it was an immigrant from Asia, with the gray wolf C. lupus evolving in Beringia later in the Pleistocene and entering mid-latitude North America during the Last Glacial Period along with its Beringian prey. In 2010 Francisco Prevosti proposed that C. dirus was a sister taxon to C. lupus. | Dire wolf | Wikipedia | 487 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
C. dirus lived in the Late Pleistocene to the early Holocene, 125,000–10,000 YBP (years before present), in North and South America. The majority of fossils from the eastern C. d. dirus have been dated 125,000–75,000 YBP, but the western fossils are not only smaller in size but more recent; thus it has been proposed that derived from However, there are disputed specimens of C. dirus that date to 250,000 YBP. Fossil specimens of C. dirus discovered at four sites in the Hay Springs area of Sheridan County, Nebraska, were named Aenocyon dirus nebrascensis (Frick 1930, undescribed), but Frick did not publish a description of them. Nowak later referred to this material as C. armbrusteri; then, in 2009, Tedford formally published a description of the specimens and noted that, although they exhibited some morphological characteristics of both C. armbrusteri and C. dirus, he referred to them only as C. dirus.
A fossil discovered in the Horse Room of the Salamander Cave in the Black Hills of South Dakota may possibly be C. dirus; if so, this fossil is one of the earliest specimens on record. It was catalogued as Canis cf. C. dirus (where cf. in Latin means confer, uncertain). The fossil of a horse found in the Horse Room provided a uranium-series dating of 252,000 YBP and the Canis cf. dirus specimen was assumed to be from the same period. C. armbrusteri and C. dirus share some characteristics (synapomorphies) that imply the latter's descent from the former. The fossil record suggests C. dirus originated around 250,000 YBP in the open terrain of the mid-continent before expanding eastward and displacing its ancestor C. armbrusteri. The first appearance of C. dirus would therefore be 250,000 YBP in California and Nebraska, and later in the rest of the United States, Canada, Mexico, Venezuela, Ecuador, Bolivia, and Peru, but the identity of these earliest fossils is not confirmed. | Dire wolf | Wikipedia | 469 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
In South America, C. dirus specimens dated to the Late Pleistocene were found along the north and west coasts, but none have been found in Argentina, an area that was inhabited by Canis gezi and Canis nehringi. Given their similarities and timeframes, it is proposed that C. gezi was the ancestor of Canis nehringi. One study found that C. dirus was more evolutionarily derived compared with C. nehringi, and was larger in the size and construction of its lower molars for more efficient predation. For this reason, some researchers have proposed that C. dirus may have originated in South America. Tedford proposed that C. armbrusteri was the common ancestor for both the North and South American wolves. Later studies concluded that C. dirus and C. nehringi were the same species, and that C. dirus had migrated from North America into South America, making it a participant in the Great American Interchange. In 2018, a study found that Canis gezi did not fall under genus Canis and should be classified under the subtribe Cerdocyonina, however no genus was proposed.
The 2020 discovery of a claimed dire wolf fossil in northeast China indicates that dire wolves may have crossed Beringia when it existed, though other researchers doubt that this specimen represents a dire wolf.
DNA evidence
DNA evidence indicates the dire wolf arose from an ancestral lineage that originated in the Americas and was separate to genus Canis.
In 1992 an attempt was made to extract a mitochondrial DNA sequence from the skeletal remains of A.d.guildayi to compare its relationship to other Canis species. The attempt was unsuccessful because these remains had been removed from the LaBrea pits and tar could not be removed from the bone material. In 2014 an attempt to extract DNA from a Columbian mammoth from the tar pits also failed, with the study concluding that organic compounds from the asphalt permeate the bones of all ancient samples from the LaBrea pits, hindering the extraction of DNA samples. | Dire wolf | Wikipedia | 420 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
In 2021, researchers sequenced the nuclear DNA (from the cell nucleus) taken from five dire wolf fossils dating from 13,000 to 50,000 years ago. The sequences indicate the dire wolf to be a highly divergent lineage which last shared a most recent common ancestor with the wolf-like canines 5.7 million years ago. The study also measured numerous dire wolf and gray wolf skeletal samples that showed their morphologies to be highly similar, which had led to the theory that the dire wolf and the gray wolf had a close evolutionary relationship. The morphological similarity between dire wolves and gray wolves was concluded to be due to convergent evolution. Members of the wolf-like canines are known to hybridize with each other but the study could find no indication of genetic admixture from the five dire wolf samples with extant North American gray wolves and coyotes nor their common ancestor. This finding indicates that the wolf and coyote lineages evolved in isolation from the dire wolf lineage.
The study proposes an early origin of the dire wolf lineage in the Americas, and that this geographic isolation allowed them to develop a degree of reproductive isolation since their divergence 5.7 million years ago. Coyotes, dholes, gray wolves, and the extinct Xenocyon evolved in Eurasia and expanded into North America relatively recently during the Late Pleistocene, therefore there was no admixture with the dire wolf. The long-term isolation of the dire wolf lineage implies that other American fossil taxa, including C. armbrusteri and C. edwardii, may also belong to the dire wolf's lineage. The study's findings are consistent with the previously proposed taxonomic classification of the dire wolf as genus Aenocyon. | Dire wolf | Wikipedia | 346 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
Radiocarbon dating
The age of most dire wolf localities is determined solely by biostratigraphy, but biostratigraphy is an unreliable indicator within asphalt deposits. Some sites have been radiocarbon dated, with dire wolf specimens from the LaBrea pits dated in calendar years as follows: 82 specimens dated 13,000–14,000YBP; 40 specimens dated 14,000–16,000YBP; 77 specimens dated 14,000–18,000YBP; 37 specimens dated 17,000–18,000YBP; 26 specimens dated 21,000–30,000YBP; 40 specimens dated 25,000–28,000YBP; and 6specimens dated 32,000–37,000YBP. A specimen from Powder Mill Creek Cave, Missouri, was dated at 13,170YBP.
Description
The average dire wolf proportions were similar to those of two modern North American wolves: the Yukon wolf (Canis lupus pambasileus) and the Northwestern wolf (Canis lupus occidentalis). The largest northern wolves today have a shoulder height of up to and a body length of . Some dire wolf specimens from Rancho LaBrea are smaller than this, and some are larger.
The dire wolf had smaller feet and a larger head when compared with a northern wolf of the same body size. The skull length could reach up to or longer, with a broader palate, frontal region, and zygomatic arches compared with the Yukon wolf. These dimensions make the skull very massive. Its sagittal crest was higher, with the inion showing a significant backward projection, and with the rear ends of the nasal bones extending relatively far back into the skull. A connected skeleton of a dire wolf from Rancho LaBrea is difficult to find because the tar allows the bones to disassemble in many directions. Parts of a vertebral column have been assembled, and it was found to be similar to that of the modern wolf, with the same number of vertebrae. | Dire wolf | Wikipedia | 418 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
Geographic differences in dire wolves were not detected until 1984, when a study of skeletal remains showed differences in a few cranio-dental features and limb proportions between specimens from California and Mexico (A.d.guildayi) and those found from the east of the Continental Divide (A.d.dirus). A comparison of limb size shows that the rear limbs of A.d.guildayi were 8% shorter than the Yukon wolf due to a significantly shorter tibia and metatarsus, and that the front limbs were also shorter due to their slightly shorter lower bones. With its comparatively lighter and smaller limbs and massive head, A.d.guildayi was not as well adapted for running as timber wolves and coyotes. A.d.dirus possessed significantly longer limbs than A.d.guildayi. The forelimbs were 14% longer than A.d.guildayi due to 10% longer humeri, 15% longer radii, and 15% longer metacarpals. The rear limbs were 10% longer than A.d.guildayi due to 10% longer femora and tibiae, and 15% longer metatarsals. A.d.dirus is comparable to the Yukon wolf in limb length. The largest A.d.dirus femur was found in Carroll Cave, Missouri, and measured .
A.d.guildayi is estimated to have weighed on average , and A.d.dirus weighed on average with some specimens being larger, but these could not have exceeded due to skeletal limits. In comparison, the average weight of the Yukon wolf is for males and for females. Individual weights for Yukon wolves can vary from to , with one Yukon wolf weighing . These figures show the average dire wolf to be similar in size to the largest modern gray wolf.
The remains of a complete male A. dirus are sometimes easy to identify compared to other Canis specimens because the baculum (penis bone) of the dire wolf is very different from that of all other living canids. A 2024 study found the baculum of a male dire wolf to be proportionally longer than the baculum of modern canids, which may be indicative of stronger competition between males and unusual behaviors among canids including non-monogamous mating.
Adaptation | Dire wolf | Wikipedia | 475 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
Ecological factors such as habitat type, climate, prey specialization, and predatory competition have been shown to greatly influence gray wolf craniodental plasticity, which is an adaptation of the cranium and teeth due to the influences of the environment. Similarly, the dire wolf was a hypercarnivore, with a skull and dentition adapted for hunting large and struggling prey; the shape of its skull and snout changed across time, and changes in the size of its body have been correlated with climate fluctuations.
Paleoecology
The last glacial period, commonly referred to as the "Ice Age", spanned 125,000–14,500YBP and was the most recent glacial period within the current ice age, which occurred during the last years of the Pleistocene era. The Ice Age reached its peak during the Last Glacial Maximum, when ice sheets began advancing from 33,000YBP and reached their maximum limits 26,500YBP. Deglaciation commenced in the Northern Hemisphere approximately 19,000YBP and in Antarctica approximately 14,500YBP, which is consistent with evidence that glacial meltwater was the primary source for an abrupt rise in sea level 14,500YBP. Access into northern North America was blocked by the Wisconsin glaciation. The fossil evidence from the Americas points to the extinction mainly of large animals, termed Pleistocene megafauna, near the end of the last glaciation. | Dire wolf | Wikipedia | 290 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
Coastal southern California from 60,000YBP to the end of the Last Glacial Maximum was cooler and with a more balanced supply of moisture than today. During the Last Glacial Maximum, the mean annual temperature decreased from down to degrees, and annual precipitation had decreased from down to . This region was unaffected by the climatic effects of the Wisconsin glaciation and is thought to have been an Ice Age refugium for animals and cold-sensitive plants. By 24,000YBP, the abundance of oak and chaparral decreased, but pines increased, creating open parklands similar to today's coastal montane/juniper woodlands. After 14,000YBP, the abundance of conifers decreased, and those of the modern coastal plant communities, including oak woodland, chaparral, and coastal sage scrub, increased. The Santa Monica Plain lies north of the city of Santa Monica and extends along the southern base of the Santa Monica Mountains, and 28,000–26,000YBP it was dominated by coastal sage scrub, with cypress and pines at higher elevations. The Santa Monica Mountains supported a chaparral community on its slopes and isolated coast redwood and dogwood in its protected canyons, along with river communities that included willow, red cedar, and sycamore. These plant communities suggest a winter rainfall similar to that of modern coastal southern California, but the presence of coast redwood now found to the north indicates a cooler, moister, and less seasonal climate than today. This environment supported large herbivores that were prey for dire wolves and their competitors.
Prey | Dire wolf | Wikipedia | 319 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
A range of animal and plant specimens that became entrapped and were then preserved in tar pits have been removed and studied so that researchers can learn about the past. The Rancho LaBrea tar pits located near Los Angeles in Southern California are a collection of pits of sticky asphalt deposits that differ in deposition time from 40,000 to 12,000YBP. Commencing 40,000YBP, trapped asphalt has been moved through fissures to the surface by methane pressure, forming seeps that can cover several square meters and be deep. A large number of dire wolf fossils have been recovered from the La Brea tar pits. Over 200,000 specimens (mostly fragments) have been recovered from the tar pits, with the remains ranging from Smilodon to squirrels, invertebrates, and plants. The time period represented in the pits includes the Last Glacial Maximum when global temperatures were lower than today, the Pleistocene–Holocene transition (Bølling-Allerød interval), the Oldest Dryas cooling, the Younger Dryas cooling from 12,800 to 11,500YBP, and the American megafaunal extinction event 12,700YBP when 90 genera of mammals weighing over became extinct.
Isotope analysis can be used to identify some chemical elements, allowing researchers to make inferences about the diet of the species found in the pits. Isotope analysis of bone collagen extracted from LaBrea specimens provides evidence that the dire wolf, Smilodon, and the American lion (Panthera atrox) competed for the same prey. Their prey included the extinct camel Camelops hesternus, the extinct bison Bison antiquus, the "dwarf" pronghorn (Capromeryx minor), the equine Equus occidentalis, and Harlan's ground sloth (Paramylodon harlani) native to North American grasslands. The Columbian mammoth (Mammuthus columbi) and the American mastodon (Mammut americanum) were rare at LaBrea. The horses remained mixed feeders and the pronghorns mixed browsers, but at the Last Glacial Maximum and its associated shift in vegetation the camels and bison were forced to rely more heavily on conifers. | Dire wolf | Wikipedia | 457 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
A study of isotope data of La Brea dire wolf fossils dated 10,000YBP provides evidence that the horse was an important prey species at the time, and that sloth, mastodon, bison, and camel were less common in the dire wolf diet. This indicates that the dire wolf was not a prey specialist, and at the close of the Late Pleistocene before its extinction it was hunting or scavenging the most available herbivores. A study based on specimens found in Cedral, San Luis Potosi found that the dire wolf primarily preyed on herbivores that consumed C4 plants and on mixed-diet herbivores.
Dentition and bite force
When compared with the dentition of genus Canis members, the dire wolf was considered the most evolutionary derived (advanced) wolf-like species in the Americas. The dire wolf could be identified separately from all other Canis species by its possession of: "P2 with a posterior cusplet; P3 with two posterior cusplets; M1 with a mestascylid, entocristed, entoconulid, and a transverse crest extending from the metaconid to the hyperconular shelf; M2 with entocristed and entoconulid."
A study of the estimated bite force at the canine teeth of a large sample of living and fossil mammalian predators, when adjusted for the body mass, found that for placental mammals the bite force at the canines (in newtons/kilogram of body weight) was greatest in the dire wolf (163), followed among the modern canids by the four hypercarnivores that often prey on animals larger than themselves: the African hunting dog (142), the gray wolf (136), the dhole (112), and the dingo (108). The bite force at the carnassials showed a similar trend to the canines. A predator's largest prey size is strongly influenced by its biomechanical limits. The morphology of the dire wolf was similar to that of its living relatives, and assuming that the dire wolf was a social hunter, then its high bite force relative to living canids suggests that it preyed on relatively large animals. The bite force rating of the bone-consuming spotted hyena (117) challenged the common assumption that high bite force in the canines and the carnassials was necessary to consume bone. | Dire wolf | Wikipedia | 497 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
A study of the cranial measurements and jaw muscles of dire wolves found no significant differences with modern gray wolves in all but 4 of 15 measures. Upper dentition was the same except that the dire wolf had larger dimensions, and the P4 had a relatively larger, more massive blade that enhanced slicing ability at the carnassial. The jaw of the dire wolf had a relatively broader and more massive temporalis muscle, able to generate slightly more bite force than the gray wolf. Due to the jaw arrangement, the dire wolf had less temporalis leverage than the gray wolf at the lower carnassial (m1) and lower p4, but the functional significance of this is not known. The lower premolars were relatively slightly larger than those of the gray wolf, and the dire wolf m1 was much larger and had more shearing ability. The dire wolf canines had greater bending strength than those of living canids of equivalent size and were similar to those of hyenas and felids. All these differences indicate that the dire wolf was able to deliver stronger bites than the gray wolf, and with its flexible and more rounded canines was better adapted for struggling with its prey.
Behavior
At La Brea, predatory birds and mammals were attracted to dead or dying herbivores that had become mired, and then these predators became trapped themselves. Herbivore entrapment was estimated to have occurred once every fifty years, and for every instance of herbivore remains found in the pits there were an estimated ten carnivores. A.d.guildayi is the most common carnivoran found at LaBrea, followed by Smilodon. Remains of dire wolves outnumber remains of gray wolves in the tar pits by a ratio of five to one. During the Last Glacial Maximum, coastal California, with a climate slightly cooler and wetter than today, is thought to have been a refuge, and a comparison of the frequency of dire wolves and other predator remains at LaBrea to other parts of California and North America indicates significantly greater abundances; therefore, the higher dire wolf numbers in the LaBrea region did not reflect the wider area. Assuming that only a few of the carnivores that were feeding became trapped, it is likely that fairly sizeable groups of dire wolves fed together on these occasions. | Dire wolf | Wikipedia | 471 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
The difference between the male and female of a species apart from their sex organs is called sexual dimorphism, and in this regard little variance exists among the canids. A study of dire wolf remains dated 15,360–14,310YBP and taken from one pit that focused on skull length, canine tooth size, and lower molar length showed little dimorphism, similar to that of the gray wolf, indicating that dire wolves lived in monogamous pairs. Their large size and highly carnivorous dentition supports the proposal that the dire wolf was a predator that fed on large prey. To kill ungulates larger than themselves, the African wild dog, the dhole, and the gray wolf depend on their jaws as they cannot use their forelimbs to grapple with prey, and they work together as a pack consisting of an alpha pair and their offspring from the current and previous years. It can be assumed that dire wolves lived in packs of relatives that were led by an alpha pair. Large and social carnivores would have been successful at defending carcasses of prey trapped in the tar pits from smaller solitary predators, and thus the most likely to become trapped themselves. The many A.d.guildayi and Smilodon remains found in the tar pits suggests that both were social predators.
All social terrestrial mammalian predators prey mostly on terrestrial herbivorous mammals with a body mass similar to the combined mass of the social group members attacking the prey animal. The large size of the dire wolf provides an estimated prey size in the range. Stable isotope analysis of dire wolf bones provides evidence that they had a preference for consuming ruminants such as bison rather than other herbivores but moved to other prey when food became scarce, and occasionally scavenged on beached whales along the Pacific coast when available. A pack of timber wolves can bring down a moose that is their preferred prey, and a pack of dire wolves bringing down a bison is conceivable. Although some studies have suggested that because of tooth breakage, the dire wolf must have gnawed bones and may have been a scavenger, its widespread occurrence and the more gracile limbs of the dire wolf indicate a predator. Like the gray wolf today, the dire wolf probably used its post-carnassial molars to gain access to marrow, but the dire wolf's larger size enabled it to crack larger bones.
Tooth breakage | Dire wolf | Wikipedia | 495 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
Tooth breakage is related to a carnivore's behavior. A study of nine modern carnivores found that one in four adults had suffered tooth breakage and that half of these breakages were of the canine teeth. The most breakage occurred in the spotted hyena that consumes all of its prey including the bone; the least breakage occurred in the African wild dog, and the gray wolf ranked in between these two. The eating of bone increases the risk of accidental fracture due to the relatively high, unpredictable stresses that it creates. The most commonly broken teeth are the canines, followed by the premolars, carnassial molars, and incisors. Canines are the teeth most likely to break because of their shape and function, which subjects them to bending stresses that are unpredictable in both direction and magnitude. The risk of tooth fracture is also higher when killing large prey.
A study of the fossil remains of large carnivores from LaBrea pits dated 36,000–10,000YBP shows tooth breakage rates of 5–17% for the dire wolf, coyote, American lion, and Smilodon, compared to 0.5–2.7% for ten modern predators. These higher fracture rates were across all teeth, but the fracture rates for the canine teeth were the same as in modern carnivores. The dire wolf broke its incisors more often when compared to the modern gray wolf; thus, it has been proposed that the dire wolf used its incisors more closely to the bone when feeding. Dire wolf fossils from Mexico and Peru show a similar pattern of breakage. A 1993 study proposed that the higher frequency of tooth breakage among Pleistocene carnivores compared with living carnivores was not the result of hunting larger game, something that might be assumed from the larger size of the former. When there is low prey availability, the competition between carnivores increases, causing them to eat faster and thus consume more bone, leading to tooth breakage. As their prey became extinct around 10,000 years ago, so did these Pleistocene carnivores, except for the coyote (which is an omnivore). | Dire wolf | Wikipedia | 452 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
A later La Brea pits study compared tooth breakage of dire wolves in two time periods. One pit contained fossil dire wolves dated 15,000YBP and another dated 13,000YBP. The results showed that the 15,000YBP dire wolves had three times more tooth breakage than the 13,000YBP dire wolves, whose breakage matched those of nine modern carnivores. The study concluded that between 15,000 and 14,000YBP prey availability was less or competition was higher for dire wolves and that by 13,000YBP, as the prey species moved towards extinction, predator competition had declined and therefore the frequency of tooth breakage in dire wolves had also declined.
Carnivores include both pack hunters and solitary hunters. The solitary hunter depends on a powerful bite at the canine teeth to subdue their prey, and thus exhibits a strong mandibular symphysis. In contrast, a pack hunter, which delivers many shallower bites, has a comparably weaker mandibular symphysis. Thus, researchers can use the strength of the mandibular symphysis in fossil carnivore specimens to determine what kind of hunter it wasa pack hunter or a solitary hunterand even how it consumed its prey. The mandibles of canids are buttressed behind the carnassial teeth to enable the animals to crack bones with their post-carnassial teeth (molars M2 and M3). A study found that the mandible buttress profile of the dire wolf was lower than that of the gray wolf and the red wolf, but very similar to the coyote and the African hunting dog. The dorsoventrally weak symphyseal region (in comparison to premolars P3 and P4) of the dire wolf indicates that it delivered shallow bites similar to its modern relatives and was therefore a pack hunter. This suggests that the dire wolf may have processed bone but was not as well adapted for it as was the gray wolf. The fact that the incidence of fracture for the dire wolf reduced in frequency in the Late Pleistocene to that of its modern relatives suggests that reduced competition had allowed the dire wolf to return to a feeding behavior involving a lower amount of bone consumption, a behavior for which it was best suited. | Dire wolf | Wikipedia | 475 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
The results of a study of dental microwear on tooth enamel for specimens of the carnivore species from LaBrea pits, including dire wolves, suggest that these carnivores were not food-stressed just before their extinction. The evidence also indicated that the extent of carcass utilization (i.e., amount consumed relative to the maximum amount possible to consume, including breakup and consumption of bones) was less than among large carnivores today. These findings indicates that tooth breakage was related to hunting behavior and the size of prey.
Climate impact
Past studies proposed that changes in dire wolf body size correlated with climate fluctuations. A later study compared dire wolf craniodental morphology from four LaBrea pits, each representing four different time periods. The results are evidence of a change in dire wolf size, dental wear and breakage, skull shape, and snout shape across time. Dire wolf body size had decreased between the start of the Last Glacial Maximum and near its ending at the warm Allerød oscillation. Evidence of food stress (food scarcity leading to lower nutrient intake) is seen in smaller body size, skulls with a larger cranial base, and shorter snout (shape neoteny and size neoteny), and more tooth breakage and wear. Dire wolves dated 17,900YBP showed all of these features, which indicates food stress. Dire wolves dated 28,000YBP also showed to a degree many of these features but were the largest wolves studied, and it was proposed that these wolves were also suffering from food stress and that wolves earlier than this date were even bigger in size. Nutrient stress is likely to lead to stronger bite forces to more fully consume carcasses and to crack bones, and with changes to skull shape to improve mechanical advantage. North American climate records reveal cyclic fluctuations during the glacial period that included rapid warming followed by gradual cooling, called Dansgaard–Oeschger events. These cycles would have caused increased temperature and aridity, and at LaBrea would have caused ecological stress and therefore food stress. A similar trend was found with the gray wolf, which in the Santa Barbara basin was originally massive, robust, and possibly convergent evolution with the dire wolf, but was replaced by more gracile forms by the start of the Holocene. | Dire wolf | Wikipedia | 470 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
{| class="wikitable" style="text-align:center;"
|+ Dire wolf information based on skull measurements
!scope="col"| Variable
!scope="col"| 28,000 YBP
!scope="col"| 26,100 YBP
!scope="col"| 17,900 YBP
!scope="col"| 13,800 YBP
|-
!scope="row"| Body size
| largest
| large
| smallest
| medium/small
|-
!scope="row"| Tooth breakage
| high
| low
| high
| low
|-
!scope="row"| Tooth wear
| high
| low
| high
| low
|-
!scope="row"| Snout shape
| shortening, largest cranial base
| average
| shortest, largest cranial base
| average
|-
!scope="row"| Tooth row shape
| robust
| –
| –
| gracile
|-
!scope="row"| DO event
| number 3 or 4
| none
| imprecise data
| imprecise data
|}
Competitors
Just before the appearance of the dire wolf, North America was invaded by the Canis subgenus Xenocyon (ancestor of the Asian dhole and the African hunting dog) that was as large as the dire wolf and more hypercarnivorous. The fossil record shows them as rare, and it is assumed that they could not compete with the newly derived dire wolf. Stable isotope analysis provides evidence that the dire wolf, Smilodon, and the American lion competed for the same prey. Other large carnivores included the extinct North American giant short-faced bear (Arctodus simus), the modern cougar (Puma concolor), the Pleistocene coyote (Canis latrans), and the Pleistocene gray wolf that was more massive and robust than today. These predators may have competed with humans who hunted for similar prey. | Dire wolf | Wikipedia | 402 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
Specimens that have been identified by morphology as Beringian wolves (C.lupus) and radiocarbon dated 25,800–14,300 YBP have been found in the Natural Trap Cave at the base of the Bighorn Mountains in Wyoming, in the western United States. The location is directly south of what would at that time have been a division between the Laurentide Ice Sheet and the Cordilleran Ice Sheet. A temporary channel between the glaciers may have existed that allowed these large, Alaskan direct competitors of the dire wolf, which were also adapted for preying on megafauna, to come south of the ice sheets. Dire wolf remains are absent north of the 42°Nlatitude in North America, therefore, this region would have been available for Beringian wolves to expand south along the glacier line. How widely they were then distributed is not known. These also became extinct at the end of the Late Pleistocene, as did the dire wolf.
After arriving in eastern Eurasia, the dire wolf would have likely faced competition from the area's most dominant, widespread predator, the eastern subspecies of cave hyena (Crocuta crocuta ultima). Competition with this species may have kept Eurasian dire wolf populations very low, leading to the paucity of dire wolf fossil remains in this otherwise well-studied fossil fauna.
Range
Dire wolf remains have been found across a broad range of habitats including the plains, grasslands, and some forested mountain areas of North America, the arid savannah of South America, and possibly the steppes of eastern Asia. The sites range in elevation from sea level to . The location of these fossil remains suggests that dire wolves lived predominantly in the open lowlands along with their prey the large herbivores. Dire wolf remains are not often found at high latitudes in North America, with the northernmost record in southern Canada. | Dire wolf | Wikipedia | 378 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
In the United States, dire wolf fossils have been reported in Arizona, California, Florida, Idaho, Indiana, Kansas, Kentucky, Missouri, Nebraska, New Mexico, Oregon, Pennsylvania, South Carolina, South Dakota, Texas, Utah, Virginia, West Virginia, Wyoming, and Nevada. The identity of fossils reported farther north than California is not confirmed. There have been five reports of unconfirmed dire wolf fossils north of 42°Nlatitude at Fossil Lake, Oregon (125,000–10,000YBP), American Falls Reservoir, Idaho (125,000–75,000YBP), Salamander Cave, South Dakota (250,000YBP), and four closely grouped sites in northern Nebraska (250,000YBP). This suggests a range restriction on dire wolves due to temperature, prey, or habitat. The major fossil-producing sites for A.d.dirus are located east of the Rocky Mountains and include Friesenhahn Cave, near San Antonio, Texas; Carroll Cave, near Richland, Missouri; and Reddick, Florida.
Localities in Mexico where dire wolf remains have been collected include ElCedazo in Aguascalientes, Comondú Municipality in Baja California Sur, ElCedral in San Luis Potosí, ElTajo Quarry near Tequixquiac, state of Mexico, Valsequillo in Puebla, Lago de Chapala in Jalisco, Loltun Cave in Yucatán, Potrecito in Sinaloa, San Josecito Cave near Aramberri in Nuevo León and Térapa in Sonora. The specimens from Térapa were confirmed as A.d.guildayi. The finds at San Josecito Cave and ElCedazo have the greatest number of individuals from a single locality. | Dire wolf | Wikipedia | 371 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
In South America, dire wolves have been dated younger than 17,000 YBP and have been reported from six localities: Muaco in the western Falcón state of Venezuela, Talara Province in Peru, Monagas state in eastern Venezuela, the Tarija Department in Bolivia, Atacama Desert of Chile, and Ecuador. If the dire wolf originated in North America, the species likely dispersed into South America via the Andean corridor, a proposed pathway for temperate mammals to migrate from Central to South America because of the favorable cool, dry, and open habitats that characterized the region at times. This most likely happened during a glacial period because the pathway then consisted of open, arid regions and savanna, whereas during inter-glacial periods it would have consisted of tropical rain forest.
In 2020, a fossil mandible (IVPP V25381) later analyzed as a dire wolf's was found in the vicinity of Harbin, northeastern China. The fossil was taxonomically described and dated 40,000 YBP. This discovery challenges previous theories that the cold temperatures and ice sheets at northern latitudes in North America would be a barrier for dire wolves, which was based on no dire wolf fossils being found above the 42° latitude in North America. It is proposed that the dire wolf followed migrating prey from mid-latitude North America then across Beringia into Eurasia. However, the 2022 study argued that the morphology and size of the specimen is inconclusive for its taxonomic determination as a dire wolf.
Extinction
During the Quaternary extinction event around 12,700YBP, 90genera of mammals weighing over became extinct. The extinction of the large carnivores and scavengers is thought to have been caused by the extinction of the megaherbivore prey upon which they depended. The cause of the extinction of the megafauna is debated but has been attributed to the impact of climatic change, competition with other species including overexploitation by newly arrived human hunters, or a combination of both. One study proposes that several extinction models should be investigated because so little is known about the biogeography of the dire wolf and its potential competitors and prey, nor how all these species interacted and responded to the environmental changes that occurred at the time of extinction. | Dire wolf | Wikipedia | 463 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
Ancient DNA and radiocarbon data indicate that local genetic populations were replaced by others within the same species or by others within the same genus. Both the dire wolf and the Beringian wolf went extinct in North America, leaving only the less carnivorous and more gracile form of the wolf to thrive, which may have outcompeted the dire wolf. One study proposes an early origin of the dire wolf lineage in the Americas which led to its reproductive isolation, such that when coyotes, dholes, gray wolves, and Xenocyon expanded into North America from Eurasia in the Late Pleistocene there could be no admixture with the dire wolf. Gray wolves and coyotes may have survived due to their ability to hybridize with other canids – such as the domestic dog – to acquire traits that resist diseases brought by taxa arriving from Eurasia. Reproductive isolation may have prevented the dire wolf from acquiring these traits. A 2023 study documented a high degree of subchondral defects in joint surfaces of dire wolf and Smilodon specimens from the La Brea Tar pits that resembled osteochondrosis dissecans. As modern dogs with this disease are inbred, the researchers suggested this would have been the case for the prehistoric species as well as they approached extinction, but cautioned that more research was needed to determine if this was also the case in specimens from other parts of the Americas.
Dire wolf remains having the youngest geological ages are dated at 9,440YBP at Brynjulfson Cave, Boone County, Missouri, 9,860YBP at Rancho La Brea, California, and 10,690YBP at La Mirada, California. Dire wolf remains have been radiocarbon dated to 8,200YBP from Whitewater Draw in Arizona, though one author has stated that radiocarbon dating of bone carbonate is unreliable. All of these dates are uncalibrated and the actual age of the remains is likely older. In South America, the most recent remains at Talara, Peru date to 9,030 ± 240 YBP (also uncalibrated), while the most recent remains of "C. nehringi" from Luján, Argentina are older than the most recent stratigraphical section of the site, dated to 10–11,000 YBP. | Dire wolf | Wikipedia | 477 | 314510 | https://en.wikipedia.org/wiki/Dire%20wolf | Biology and health sciences | Canines | Animals |
In geometry, an octagon () is an eight-sided polygon or 8-gon.
A regular octagon has Schläfli symbol {8} and can also be constructed as a quasiregular truncated square, t{4}, which alternates two types of edges. A truncated octagon, t{8} is a hexadecagon, {16}. A 3D analog of the octagon can be the rhombicuboctahedron with the triangular faces on it like the replaced edges, if one considers the octagon to be a truncated square.
Properties
The sum of all the internal angles of any octagon is 1080°. As with all polygons, the external angles total 360°.
If squares are constructed all internally or all externally on the sides of an octagon, then the midpoints of the segments connecting the centers of opposite squares form a quadrilateral that is both equidiagonal and orthodiagonal (that is, whose diagonals are equal in length and at right angles to each other).
The midpoint octagon of a reference octagon has its eight vertices at the midpoints of the sides of the reference octagon. If squares are constructed all internally or all externally on the sides of the midpoint octagon, then the midpoints of the segments connecting the centers of opposite squares themselves form the vertices of a square.
Regularity
A regular octagon is a closed figure with sides of the same length and internal angles of the same size. It has eight lines of reflective symmetry and rotational symmetry of order 8. A regular octagon is represented by the Schläfli symbol {8}.
The internal angle at each vertex of a regular octagon is 135° ( radians). The central angle is 45° ( radians).
Area
The area of a regular octagon of side length a is given by
In terms of the circumradius R, the area is
In terms of the apothem r (see also inscribed figure), the area is
These last two coefficients bracket the value of pi, the area of the unit circle.
The area can also be expressed as | Octagon | Wikipedia | 462 | 314575 | https://en.wikipedia.org/wiki/Octagon | Mathematics | Two-dimensional space | null |
where S is the span of the octagon, or the second-shortest diagonal; and a is the length of one of the sides, or bases. This is easily proven if one takes an octagon, draws a square around the outside (making sure that four of the eight sides overlap with the four sides of the square) and then takes the corner triangles (these are 45–45–90 triangles) and places them with right angles pointed inward, forming a square. The edges of this square are each the length of the base.
Given the length of a side a, the span S is
The span, then, is equal to the silver ratio times the side, a.
The area is then as above:
Expressed in terms of the span, the area is
Another simple formula for the area is
More often the span S is known, and the length of the sides, a, is to be determined, as when cutting a square piece of material into a regular octagon. From the above,
The two end lengths e on each side (the leg lengths of the triangles (green in the image) truncated from the square), as well as being may be calculated as
Circumradius and inradius
The circumradius of the regular octagon in terms of the side length a is
and the inradius is
(that is one-half the silver ratio times the side, a, or one-half the span, S)
The inradius can be calculated from the circumradius as
Diagonality
The regular octagon, in terms of the side length a, has three different types of diagonals:
Short diagonal;
Medium diagonal (also called span or height), which is twice the length of the inradius;
Long diagonal, which is twice the length of the circumradius.
The formula for each of them follows from the basic principles of geometry. Here are the formulas for their length:
Short diagonal: ;
Medium diagonal: ; (silver ratio times a)
Long diagonal: .
Construction | Octagon | Wikipedia | 418 | 314575 | https://en.wikipedia.org/wiki/Octagon | Mathematics | Two-dimensional space | null |
A regular octagon at a given circumcircle may be constructed as follows:
Draw a circle and a diameter AOE, where O is the center and A, E are points on the circumcircle.
Draw another diameter GOC, perpendicular to AOE.
(Note in passing that A,C,E,G are vertices of a square).
Draw the bisectors of the right angles GOA and EOG, making two more diameters HOD and FOB.
A,B,C,D,E,F,G,H are the vertices of the octagon.
A regular octagon can be constructed using a straightedge and a compass, as 8 = 23, a power of two:
The regular octagon can be constructed with meccano bars. Twelve bars of size 4, three bars of size 5 and two bars of size 6 are required.
Each side of a regular octagon subtends half a right angle at the centre of the circle which connects its vertices. Its area can thus be computed as the sum of eight isosceles triangles, leading to the result:
for an octagon of side a.
Standard coordinates
The coordinates for the vertices of a regular octagon centered at the origin and with side length 2 are:
(±1, ±(1+))
(±(1+), ±1).
Dissectibility
Coxeter states that every zonogon (a 2m-gon whose opposite sides are parallel and of equal length) can be dissected into m(m-1)/2 parallelograms.
In particular this is true for regular polygons with evenly many sides, in which case the parallelograms are all rhombi. For the regular octagon, m=4, and it can be divided into 6 rhombs, with one example shown below. This decomposition can be seen as 6 of 24 faces in a Petrie polygon projection plane of the tesseract. The list defines the number of solutions as eight, by the eight orientations of this one dissection. These squares and rhombs are used in the Ammann–Beenker tilings.
Skew | Octagon | Wikipedia | 457 | 314575 | https://en.wikipedia.org/wiki/Octagon | Mathematics | Two-dimensional space | null |
A skew octagon is a skew polygon with eight vertices and edges but not existing on the same plane. The interior of such an octagon is not generally defined. A skew zig-zag octagon has vertices alternating between two parallel planes.
A regular skew octagon is vertex-transitive with equal edge lengths. In three dimensions it is a zig-zag skew octagon and can be seen in the vertices and side edges of a square antiprism with the same D4d, [2+,8] symmetry, order 16.
Petrie polygons
The regular skew octagon is the Petrie polygon for these higher-dimensional regular and uniform polytopes, shown in these skew orthogonal projections of in A7, B4, and D5 Coxeter planes.
Symmetry
The regular octagon has Dih8 symmetry, order 16. There are three dihedral subgroups: Dih4, Dih2, and Dih1, and four cyclic subgroups: Z8, Z4, Z2, and Z1, the last implying no symmetry.
On the regular octagon, there are eleven distinct symmetries. John Conway labels full symmetry as r16. The dihedral symmetries are divided depending on whether they pass through vertices (d for diagonal) or edges (p for perpendiculars) Cyclic symmetries in the middle column are labeled as g for their central gyration orders. Full symmetry of the regular form is r16 and no symmetry is labeled a1.
The most common high symmetry octagons are p8, an isogonal octagon constructed by four mirrors can alternate long and short edges, and d8, an isotoxal octagon constructed with equal edge lengths, but vertices alternating two different internal angles. These two forms are duals of each other and have half the symmetry order of the regular octagon.
Each subgroup symmetry allows one or more degrees of freedom for irregular forms. Only the g8 subgroup has no degrees of freedom but can be seen as directed edges.
Use | Octagon | Wikipedia | 435 | 314575 | https://en.wikipedia.org/wiki/Octagon | Mathematics | Two-dimensional space | null |
The octagonal shape is used as a design element in architecture. The Dome of the Rock has a characteristic octagonal plan. The Tower of the Winds in Athens is another example of an octagonal structure. The octagonal plan has also been in church architecture such as St. George's Cathedral, Addis Ababa, Basilica of San Vitale (in Ravenna, Italia), Castel del Monte (Apulia, Italia), Florence Baptistery, Zum Friedefürsten Church (Germany) and a number of octagonal churches in Norway. The central space in the Aachen Cathedral, the Carolingian Palatine Chapel, has a regular octagonal floorplan. Uses of octagons in churches also include lesser design elements, such as the octagonal apse of Nidaros Cathedral.
Architects such as John Andrews have used octagonal floor layouts in buildings for functionally separating office areas from building services, such as in the Intelsat Headquarters of Washington or Callam Offices in Canberra.
Derived figures
Related polytopes
The octagon, as a truncated square, is first in a sequence of truncated hypercubes:
As an expanded square, it is also first in a sequence of expanded hypercubes: | Octagon | Wikipedia | 240 | 314575 | https://en.wikipedia.org/wiki/Octagon | Mathematics | Two-dimensional space | null |
A pebble is a clast of rock with a particle size of based on the Udden-Wentworth scale of sedimentology. Pebbles are generally considered larger than granules ( in diameter) and smaller than cobbles ( in diameter). A rock made predominantly of pebbles is termed a conglomerate. Pebble tools are among the earliest known man-made artifacts, dating from the Palaeolithic period of human history.
A beach composed chiefly of surface pebbles is commonly termed a shingle beach. This type of beach has armoring characteristics with respect to wave erosion, as well as ecological niches that provide habitat for animals and plants.
Inshore banks of shingle (large quantities of pebbles) exist in some locations, such as the entrance to the River Ore, England, where the moving banks of shingle give notable navigational challenges.
Pebbles come in various colors and textures and can have streaks, known as veins, of quartz or other minerals. Pebbles are mostly smooth but, dependent on how frequently they come in contact with the sea, they can have marks of contact with other rocks or other pebbles. Pebbles left above the high water mark may have growths of organisms such as lichen on them, signifying the lack of contact with seawater.
Location
Pebbles on Earth exist in two types of locations – on the beaches of various oceans and seas, and inland where ancient seas used to cover the land. Then, when the seas retreated, the rocks became landlocked. Here, they entered lakes and ponds, and form in rivers, travelling into estuaries where the smoothing continues in the sea.
Beach pebbles and river pebbles (also known as river rock) are distinct in their geological formation and appearance.
Manufactured Pebbles-These are made from natural stones such as marble, granite, and sandstone. Manufactured Pebbles are designed to specified sizes and forms, making them flexible for many purposes.
Beach | Pebble | Wikipedia | 378 | 314610 | https://en.wikipedia.org/wiki/Pebble | Physical sciences | Sedimentology | Earth science |
Beach pebbles form gradually over time as the ocean water washes over loose rock particles. The result is a smooth, rounded appearance. The typical size range is from 2 mm to 50 mm. The colors range from translucent white to black, and include shades of yellow, brown, red and green. Some of the more plentiful pebble beaches are along the coast of the Pacific Ocean, beginning in Canada and extending down to the tip of South America in Argentina. Other pebble beaches are in northern Europe (particularly on the beaches of the Norwegian Sea), along the coast of the U.K. and Ireland, on the shores of Australia, and around the islands of Indonesia and Japan.
Inland
Inland pebbles (river pebbles of river rock) are usually found along the shores of large rivers and lakes. These pebbles form as the flowing water washes over rock particles on the bottom and along the shores of the river. The smoothness and color of river pebbles depends on several factors, such as the composition of the soil of the river banks, the chemical characteristics of the water, and the speed of the current. Because river current is gentler than the ocean waves, river pebbles are usually not as smooth as beach pebbles. The most common colors of river rock are black, grey, green, brown and white.
Human use
Beach pebbles and river pebbles are used for a variety of purposes, both outdoors and indoors. They can be sorted by colour and size, and they can also be polished to improve the texture and colour. Outdoors, beach pebbles are often used for landscaping, construction and as decorative elements. Beach pebbles are often used to cover walkways and driveways, around pools, in and around plant containers, on patios and decks. Beach and river pebbles are also used to create water-smart gardens in areas where water is scarce. Small pebbles are also used to create living spaces and gardens on the rooftops of buildings. Indoors, pebbles can be used as bookends and paperweights. Large pebbles are also used to create "pet rocks" for children.
Mars
On Mars, slabs of pebbly conglomerate rock have been found and have been interpreted by scientists as having formed in an ancient streambed. The gravels, which were discovered by NASA's Mars rover Curiosity, range from the size of sand particles to the size of golf balls. Analysis has shown that the pebbles were deposited by a stream that flowed at walking pace and was ankle- to hip-deep.
Gallery | Pebble | Wikipedia | 499 | 314610 | https://en.wikipedia.org/wiki/Pebble | Physical sciences | Sedimentology | Earth science |
Enamel paint is paint that air-dries to a hard, usually glossy, finish, used for coating surfaces that are outdoors or otherwise subject to hard wear or variations in temperature; it should not be confused with decorated objects in "painted enamel", where vitreous enamel is applied with brushes and fired in a kiln. The name is something of a misnomer, as in reality most commercially available enamel paints are significantly softer than either vitreous enamel or stoved synthetic resins, and are totally different in composition; vitreous enamel is applied as a powder or paste and then fired at high temperature. There is no generally accepted definition or standard for use of the term "enamel paint", and not all enamel-type paints may use it.
Paint
Typically the term "enamel paint" is used to describe oil-based covering products, usually with a significant amount of gloss in them, however recently many latex or water-based paints have adopted the term as well. The term today means "hard surfaced paint" and usually is in reference to paint brands of higher quality, floor coatings of a high gloss finish, or spray paints. Most enamel paints are alkyd resin based. Some enamel paints have been made by adding varnish to oil-based paint.
Although "enamels" and "painted enamel" in art normally refer to vitreous enamel, in the 20th century some artists used commercial enamel paints in art, including Pablo Picasso (mixing it with oil paint), Hermann-Paul, Jackson Pollock, and Sidney Nolan. The Trial (1947) is one of a number of works by Nolan to use enamel paint, usually Ripolin, a commercial paint not intended for art, also Picasso's usual brand. Some "enamel paints" are now produced specifically for artists. | Enamel paint | Wikipedia | 364 | 314650 | https://en.wikipedia.org/wiki/Enamel%20paint | Technology | Artist's and drafting tools | null |
Enamels paints can also refer to nitrocellulose based paints, one of the first modern commercial paints of the 20th century. They have since been superseded by new synthetic coatings like alkyd, acrylic and vinyl, due to toxicity, safety, and conservation (tendency to age yellow) concerns. In art has been used also by Pollock with the commercial paint named Duco. The artist experimented and created with many types of commercial or house paints during his career. Other artists: "after discovering various types of industrial materials produced in the United States in the 1930s, Siqueiros' produced most of his easel works with uncommon materials which include Duco paint, a DuPont brand name for pyroxyline paint, a tough and resilient type of nitro-cellulose paint manufactured for the automotive industry". Nitro-cellulose enamels are also commonly known as modern lacquers. Enamel paint comes in a variety of hues and can be custom blended to produce a particular tint. It is also available in water-based and solvent-based formulations, with solvent-based enamel being more prevalent in industrial applications. For the greatest results, use a high-quality brush, roller, or spray gun when applying enamel paint. When dried, enamel paint forms a durable, hard-wearing surface that resists chipping, fading, and discoloration, making it a great choice for a wide range of surfaces and applications. | Enamel paint | Wikipedia | 301 | 314650 | https://en.wikipedia.org/wiki/Enamel%20paint | Technology | Artist's and drafting tools | null |
Uses and categories
Floor enamel – May be used for concrete, stairs, basements, porches, and patios.
Fast dry enamel – Can dry within 10–15 minutes of application. Ideal for refrigerators, counters, and other industrial finishes.
High-temp enamel – May be used for engines, brake calipers, exhaust pipe and BBQs.
Enamel paint is also used on wood to make it resistant to the elements via the waterproofing and rotproofing properties of enamel. Generally, treated surfaces last much longer and are much more resistant to wear than untreated surfaces.
Model building – Xtracolor and Humbrol are mainstream UK brands. Colourcoats model paint is a high quality brand with authentic accurate military colours. Testors, a US company, offers the Floquil, Pactra, Model Master and Testors brands.
Nail enamel – to color nails, it comes in many varieties for fast drying, color retention, gloss retention, etc.
Epoxy enamel, polyurethane enamel, etc. used in protective coating / industrial painting purpose in chemical and petrochemical industries for anti-corrosion purposes. | Enamel paint | Wikipedia | 233 | 314650 | https://en.wikipedia.org/wiki/Enamel%20paint | Technology | Artist's and drafting tools | null |
Clostridium is a genus of anaerobic, Gram-positive bacteria. Species of Clostridium inhabit soils and the intestinal tracts of animals, including humans. This genus includes several significant human pathogens, including the causative agents of botulism and tetanus. It also formerly included an important cause of diarrhea, Clostridioides difficile, which was reclassified into the Clostridioides genus in 2016.
History
In the late 1700s, Germany experienced several outbreaks of an illness connected to eating specific sausages. In 1817, the German neurologist Justinus Kerner detected rod-shaped cells in his investigations into this so-called sausage poisoning. In 1897, the Belgian biology professor Emile van Ermengem published his finding of an endospore-forming organism he isolated from spoiled ham. Biologists classified van Ermengem's discovery along with other known gram-positive spore formers in the genus Bacillus. This classification presented problems, however, because the isolate grew only in anaerobic conditions, but Bacillus grew well in oxygen.
Circa 1880, in the course of studying fermentation and butyric acid synthesis, a scientist surnamed Prazmowski first assigned a binomial name to Clostridium butyricum. The mechanisms of anaerobic respiration were still not yet well elucidated at that time, so taxonomy of anaerobes was still developing.
In 1924, Ida A. Bengtson separated van Ermengem's microorganisms from the Bacillus group and assigned them to the genus Clostridium. By Bengtson's classification scheme, Clostridium contained all of the anaerobic endospore-forming rod-shaped bacteria, except the genus Desulfotomaculum.
Taxonomy
As of October 2022, there are 164 validly published species in Clostridium. | Clostridium | Wikipedia | 403 | 314788 | https://en.wikipedia.org/wiki/Clostridium | Biology and health sciences | Gram-positive bacteria | Plants |
The genus, as traditionally defined, contains many organisms not closely related to its type species. The issue was originally illustrated in full detail by a rRNA phylogeny from Collins 1994, which split the traditional genus (now corresponding to a large slice of Clostridia) into twenty clusters, with cluster I containing the type species Clostridium butyricum and its close relatives. Over the years, this has resulted in many new genera being split out, with the ultimate goal of constraining Clostridium to cluster I.
"Clostridium" cluster XIVa (now Lachnospiraceae) and "Clostridium" cluster IV (now Ruminococcaceae) efficiently ferment plant polysaccharide composing dietary fiber, making them important and abundant taxa in the rumen and the human large intestine. As mentioned before, these clusters are not part of current Clostridium, and use of these terms should be avoided due to ambiguous or inconsistent usage.
Biochemistry
Species of Clostridium are obligate anaerobe and capable of producing endospores. They generally stain gram-positive, but as well as Bacillus, are often described as Gram-variable, because they show an increasing number of gram-negative cells as the culture ages.
The normal, reproducing cells of Clostridium, called the vegetative form, are rod-shaped, which gives them their name, from the Greek κλωστήρ or spindle. Clostridium endospores have a distinct bowling pin or bottle shape, distinguishing them from other bacterial endospores, which are usually ovoid in shape. The Schaeffer–Fulton stain (0.5% malachite green in water) can be used to distinguish endospores of Bacillus and Clostridium from other microorganisms.
Clostridium can be differentiated from the also endospore forming genus Bacillus by its obligate anaerobic growth, the shape of endospores and the lack of catalase. Species of Desulfotomaculum form similar endospores and can be distinguished by their requirement for sulfur.
Glycolysis and fermentation of pyruvic acid by Clostridia yield the end products butyric acid, butanol, acetone, isopropanol, and carbon dioxide. | Clostridium | Wikipedia | 506 | 314788 | https://en.wikipedia.org/wiki/Clostridium | Biology and health sciences | Gram-positive bacteria | Plants |
There is a commercially available polymerase chain reaction (PCR) test kit (Bactotype) for the detection of C. perfringens and other pathogenic bacteria.
Biology and pathogenesis
Clostridium species are readily found inhabiting soils and intestinal tracts. Clostridium species are also a normal inhabitant of the healthy lower reproductive tract of females.
The main species responsible for disease in humans are:
Clostridium botulinum can produce botulinum toxin in food or wounds and can cause botulism. This same toxin is known as Botox and is used in cosmetic surgery to paralyze facial muscles to reduce the signs of aging; it also has numerous other therapeutic uses.
Clostridium perfringens causes a wide range of symptoms, from food poisoning to cellulitis, fasciitis, necrotic enteritis and gas gangrene.
Clostridium tetani causes tetanus.
Several more pathogenic species, that were previously described in Clostridium, have been found to belong to other genera.
Clostridium difficile, now placed in Clostridioides.
Clostridium histolyticum, now placed in Hathewaya.
Clostridium sordellii, now placed in Paraclostridium, can cause a fatal infection in exceptionally rare cases after medical abortions.
Treatment
In general, the treatment of clostridial infection is high-dose penicillin G, to which the organism has remained susceptible. Clostridium welchii and Clostridium tetani respond to sulfonamides. Clostridia are also susceptible to tetracyclines, carbapenems (imipenem), metronidazole, vancomycin, and chloramphenicol. | Clostridium | Wikipedia | 381 | 314788 | https://en.wikipedia.org/wiki/Clostridium | Biology and health sciences | Gram-positive bacteria | Plants |
The vegetative cells of clostridia are heat-labile and are killed by short heating at temperatures above . The thermal destruction of Clostridium spores requires higher temperatures (above , for example in an autoclave) and longer cooking times (20 min, with a few exceptional cases of more than 50 min recorded in the literature). Clostridia and Bacilli are quite radiation-resistant, requiring doses of about 30 kGy, which is a serious obstacle to the development of shelf-stable irradiated foods for general use in the retail market. The addition of lysozyme, nitrate, nitrite and propionic acid salts inhibits clostridia in various foods.
Fructooligosaccharides (fructans) such as inulin, occurring in relatively large amounts in a number of foods such as chicory, garlic, onion, leek, artichoke, and asparagus, have a prebiotic or bifidogenic effect, selectively promoting the growth and metabolism of beneficial bacteria in the colon, such as Bifidobacteria and Lactobacilli, while inhibiting harmful ones, such as clostridia, fusobacteria, and Bacteroides. | Clostridium | Wikipedia | 262 | 314788 | https://en.wikipedia.org/wiki/Clostridium | Biology and health sciences | Gram-positive bacteria | Plants |
Use
Clostridium thermocellum can use lignocellulosic waste and generate ethanol, thus making it a possible candidate for use in production of ethanol fuel. It also has no oxygen requirement and is thermophilic, which reduces cooling cost.
Clostridium acetobutylicum was first used by Chaim Weizmann to produce acetone and biobutanol from starch in 1916 for the production of cordite (smokeless gunpowder).
Clostridium botulinum produces a potentially lethal neurotoxin used in a diluted form in the drug Botox, which is carefully injected to nerves in the face, which prevents the movement of the expressive muscles of the forehead, to delay the wrinkling effect of aging. It is also used to treat spasmodic torticollis and provides relief for around 12 to 16 weeks.
Clostridium butyricum MIYAIRI 588 strain is marketed in Japan, Korea, and China for Clostridium difficile prophylaxis due to its reported ability to interfere with the growth of the latter.
Clostridium histolyticum has been used as a source of the enzyme collagenase, which degrades animal tissue. Clostridium species excrete collagenase to eat through tissue and, thus, help the pathogen spread throughout the body. The medical profession uses collagenase for the same reason in the débridement of infected wounds. Hyaluronidase, deoxyribonuclease, lecithinase, leukocidin, protease, lipase, and hemolysin are also produced by some clostridia that cause gas gangrene.
Clostridium ljungdahlii, recently discovered in commercial chicken wastes, can produce ethanol from single-carbon sources including synthesis gas, a mixture of carbon monoxide and hydrogen, that can be generated from the partial combustion of either fossil fuels or biomass.
Clostridium butyricum converts glycerol to 1,3-propanediol.
Genes from Clostridium thermocellum have been inserted into transgenic mice to allow the production of endoglucanase. The experiment was intended to learn more about how the digestive capacity of monogastric animals could be improved. | Clostridium | Wikipedia | 494 | 314788 | https://en.wikipedia.org/wiki/Clostridium | Biology and health sciences | Gram-positive bacteria | Plants |
Nonpathogenic strains of Clostridium may help in the treatment of diseases such as cancer. Research shows that Clostridium can selectively target cancer cells. Some strains can enter and replicate within solid tumors. Clostridium could, therefore, be used to deliver therapeutic proteins to tumours. This use of Clostridium has been demonstrated in a variety of preclinical models.
Mixtures of Clostridium species, such as Clostridium beijerinckii, Clostridium butyricum, and species from other genera have been shown to produce biohydrogen from yeast waste. | Clostridium | Wikipedia | 130 | 314788 | https://en.wikipedia.org/wiki/Clostridium | Biology and health sciences | Gram-positive bacteria | Plants |
Cruise ships are large passenger ships used mainly for vacationing. Unlike ocean liners, which are used for transport, cruise ships typically embark on round-trip voyages to various ports of call, where passengers may go on tours known as "shore excursions".
Modern cruise ships tend to have less hull strength, speed, and agility compared to ocean liners. However, they have added amenities to cater to water tourists, with recent vessels being described as "balcony-laden floating condominiums".
there were 302 cruise ships operating worldwide, with a combined capacity of 664,602 passengers. Cruising has become a major part of the tourism industry, with an estimated market of $29.4 billion per year, and over 19 million passengers carried worldwide annually . The industry's rapid growth saw nine or more newly built ships catering to a North American clientele added every year since 2001, as well as others servicing European clientele until the COVID-19 pandemic in 2020 saw the entire industry all but shut down. The average age of a cruise ship in 2024 is 17.5 years. The construction market for cruise ships is dominated by three European companies and one Asian company.
Operators of cruise ships are known as cruise lines. Cruise ships are organized much like floating hotels, with a complete hospitality staff in addition to the usual ship's crew. Traditionally, the ships' restaurants organize two dinner services per day, early dining and late dining, and passengers are allocated a set dining time for the entire cruise; a recent trend is to allow diners to dine whenever they want. Besides the dining room, modern cruise ships often contain one or more casual buffet-style eateries. Most cruise ships sail the Caribbean or the Mediterranean. Others operate elsewhere in places like Alaska, the South Pacific, and the Baltic Sea. Large cruise ships have been identified as one of the major causes of overtourism.
History
Origins
Italy, a traditional focus of the Grand Tour, offered an early cruise experience on the Francesco I, flying the flag of the Kingdom of the Two Sicilies. Built in 1831, the Francesco I sailed from Naples in early June 1833, preceded by an advertising campaign. Nobles, authorities, and royal princes from all over Europe boarded the cruise ship, which sailed in just over three months to Taormina, Catania, Syracuse, Malta, Corfu, Patras, Delphi, Zante, Athens, Smyrna and Constantinople, providing passengers with excursions and guided tours. | Cruise ship | Wikipedia | 507 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
P&O first introduced passenger-cruising services in 1844, advertising sea tours to destinations such as Gibraltar, Malta and Athens, sailing from Southampton. The forerunner of modern cruise holidays, these voyages were the first of their kind. P&O Cruises is the world's oldest cruise line. The company later introduced round trips to destinations such as Alexandria and Constantinople. It underwent a period of rapid expansion in the latter half of the 19th century, commissioning larger and more luxurious ships to serve the steadily expanding market. Notable ships of the era include built in 1880, which became the first ship built with a total steel superstructure, and built in 1889.
The cruise of in the Mediterranean and the Near East from 22 January to 22 March 1891, with 241 passengers including Albert Ballin and wife themselves, is often stated to have been the first ever cruise. Christian Wilhelm Allers published an illustrated account of it as Backschisch.
The first vessel built exclusively for luxury cruising was of the German Empire, designed by Albert Ballin, general manager of the Hamburg-America Line. The ship was completed in 1900.
The practice of luxury cruising made steady inroads into the more established market for transatlantic crossings. In the competition for passengers, ocean liners – being the most famous example – added luxuries such as fine dining, luxury services, and staterooms with finer appointments. In the late-19th century, Albert Ballin, director of the Hamburg-America Line, was the first to send his transatlantic ships out on long southern cruises during the worst of the North Atlantic winter seasons. Other companies followed suit. Some of them built specialized ships designed for easy transformation between summer crossings and winter cruising.
In 1897 three luxury liners, all European-owned, offered transportation between Europe and North America. In 1906 the number had increased to seven. The British Inman Line owned , the Cunard Line had and . The White Star Line owned and . La Lorraine and La Savoie sailed for the French Compagnie Générale Transatlantique.
From luxury ocean liners to "megaship" cruising
Modern cruise ships tend to have less hull strength, speed, and agility compared to ocean liners. | Cruise ship | Wikipedia | 441 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
With the advent of large passenger jet aircraft in the 1960s, intercontinental travelers switched from ships to planes, sending the ocean liner trade into a terminal decline. Certain characteristics of older ocean liners made them unsuitable for cruising duties, such as high fuel consumption, deep draught preventing them from entering shallow ports, and cabins (often windowless) designed to maximize passenger numbers rather than comfort. In the late 1950s and 1960s, ships such as Holland America Line's (1959), the French Line's (1961), and Cunard Line's RMS (1969) were designed to serve the dual purposes of ocean liner during the northern hemisphere summer months and cruise ship in the winter, incorporating doors and baffles that could be open or closed to divide classes or open the ship to one class, wherein all passengers received roughly the same quality berthing and most of the same facilities. (Passengers in cabins in certain grades on the Queen Elizabeth 2 had access only to certain dining rooms).
Ocean liner services almost ceased in the 1970s and 1980s. The Rotterdam was put on permanent cruise service in 1968, while the France (at the time the largest passenger vessel in the world) was mothballed in 1974, sold to Norwegian Cruise Line in 1979, and after major renovations relaunched as in 1980, thus becoming the first "mega-cruise ship". The main exception was Cunard's Queen Elizabeth 2: although being put on more cruises, she maintained the regular transatlantic crossing tradition throughout the year, but with a stronger focus on leisure passengers, catering to a niche market of those who appreciated the several days at sea. International celebrities were hired to perform acts on board, along with cabarets, and with the addition of a casino and other entertainment amenities, the crossing was advertised as a vacation in itself.
The 1977–1986 television series The Love Boat helped to popularize the concept as a romantic opportunity for couples. Industry experts credit the series with increasing interest in the cruise industry, especially for those that weren't newlyweds or senior citizens, and for the resulting demand to spur investment in new ships instead of conversions. The influence was particularly notable for Princess Cruises, a line that partnered with the series and received a great deal of attention as a result. | Cruise ship | Wikipedia | 451 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Contemporary cruise ships built in the late 1980s and later, such as the which broke the size record held for decades by Norway, showed characteristics of size once reserved for ocean liners. The Sovereign-class ships were the first "megaships" to be built specifically for the mass cruising market. They also were the first series of cruise ships to include a multi-story lobby with a glass elevator and had a single deck devoted entirely to cabins with private balconies, instead of oceanview cabins. Other cruise lines soon launched ships with similar attributes, such as the , leading up to the Panamax-type , designed such that two-thirds of the oceanview staterooms have balconies. As the veranda suites were particularly lucrative for cruise lines, something which was lacking in older ocean liners, recent cruise ships have been designed to maximize such amenities and have been described as "balcony-laden floating condominiums".
Until 1975–1980, cruises offered shuffleboard, deck chairs, "drinks with umbrellas and little else for a few hundred passengers". After 1980, they offered increasing amenities. As of 2010, city-sized ships have dozens of amenities.
There have been nine or more new cruise ships added every year since 2001, including the 11 members of the aforementioned Vista class, and all at or greater. The only actual ocean liner to be completed in recent years has been Cunard Line's in 2004. Following the retirement of her running mate Queen Elizabeth 2 in November 2008, Queen Mary 2 is the only liner operating on scheduled transatlantic service, though she also sees significant service on cruise routes.
Queen Mary 2 was for a time the largest passenger ship before being surpassed by Royal Caribbean International's vessels in 2006. The Freedom-class ships were in turn overtaken by RCI's own vessels which entered service in 2009 and 2010. A distinctive feature of the Oasis-class ships is the split, atrium structure, made possible by the hull's extraordinary width, with the 6-deck high Central Park and Boardwalk outdoor areas running down the middle of the ship and verandas on all decks. | Cruise ship | Wikipedia | 427 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
In two short decades (1988–2009), the largest class cruise ships have grown a third longer (), doubled their widths (), nearly tripled the total passenger count (2,744 to 7,600), and more than tripled in volume (73,000 to 248,000 GT). Also, the "megaships" went from a single deck with verandas to all decks with verandas.
there were 302 cruise ships operating worldwide, with a combined capacity of 664,602 passengers. Cruising has become a major part of the tourism industry, with an estimated market of $29.4 billion per year, and over 19 million passengers carried worldwide annually . The industry's rapid growth saw nine or more newly built ships catering to a North American clientele added every year since 2001, as well as others servicing European clientele until the COVID-19 pandemic in 2020 saw the entire industry all but shut down. The average age of a cruise ship in 2024 is 17.5 years.
Cruise lines
Operators of cruise ships are known as cruise lines, which are companies that sell cruises to the public. Cruise lines have a dual character; they are partly in the transportation business, and partly in the leisure entertainment business, a duality that carries down into the ships themselves, which have both a crew headed by the ship's captain, and a hospitality staff headed by the equivalent of a hotel manager. Among cruise lines, some are direct descendants of the traditional passenger shipping lines (such as Cunard), while others were founded from the 1960s specifically for cruising.
Historically, the cruise ship business has been volatile. The ships are large capital investments with high operating costs. A persistent decrease in bookings can put a company in financial jeopardy. Cruise lines have sold, renovated, or renamed their ships to keep up with travel trends. Cruise lines operate their ships almost constantly. If the maintenance is unscheduled, it can result, potentially, in thousands of dissatisfied customers. | Cruise ship | Wikipedia | 410 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
A wave of failures and consolidations in the 1990s led to many cruise lines being bought by much larger holding companies and continue to operate as "brands" or subsidiaries of the holding company. Brands continue to be maintained partly because of the expectation of repeat customer loyalty, and also to offer different levels of quality and service. For instance, Carnival Corporation & plc owns both Carnival Cruise Line, whose former image were vessels that had a reputation as "party ships" for younger travelers, but have become large, modern, yet still profitable, as well as Holland America Line and Cunard Line, whose ships cultivate an image of classic elegance. In 2004, Carnival had merged Cunard's headquarters with that of Princess Cruises in Santa Clarita, California so that administrative, financial and technology services could be combined, ending Cunard's history where it had operated as a standalone company (subsidiary) regardless of parent ownership. However, Cunard did regain some independence in 2009 when its headquarters were moved to Carnival House in Southampton.
The common practice in the cruise industry in listing cruise ship transfers and orders is to list the smaller operating company, not the larger holding corporation, as the recipient cruise line of the sale, transfer, or new order. In other words, Carnival Cruise Line and Holland America Line, for example, are the cruise lines from this common industry practice point of view; whereas Carnival Corporation & plc and Royal Caribbean Group, for example, can be considered holding corporations of cruise lines. This industry practice of using the smaller operating company, not the larger holding corporation, is also followed in the list of cruise lines and in member-based reviews of cruise lines. | Cruise ship | Wikipedia | 332 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Some cruise lines have specialties; for example, Saga Cruises only allows passengers over 50 years old aboard their ships, and Star Clippers and formerly Windjammer Barefoot Cruises and Windstar Cruises only operate tall ships. Regent Seven Seas Cruises operates medium-sized vessels—smaller than the "megaships" of Carnival and Royal Caribbean—designed such that virtually all of their suites are balconies. Several specialty lines offer "expedition cruising" or only operate small ships, visiting certain destinations such as the Arctic and Antarctica, or the Galápagos Islands. , which formerly operated as part of the United States Merchant Marine during World War II before being converted to a museum ship, still gets underway several times a year for six-hour "Living History Cruises" that take the ship through Baltimore Harbor, down the Patapsco River, and into the Chesapeake Bay, and she is also the largest cruise ship operating under the American flag on the United States East Coast.
Currently the three largest cruise line holding companies and operators in the world are Carnival Corporation & plc, Royal Caribbean Group and Norwegian Cruise Line Holdings.
As an industry, the total number of cabins on all of the world's cruise ships amount to less than 2% of the world's hotel rooms.
Organization
Cruise ships are organized much like floating hotels, with a complete hospitality staff in addition to the usual ship's crew. It is not uncommon for the most luxurious ships to have more crew and staff than passengers.
Dining | Cruise ship | Wikipedia | 296 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Dining on almost all cruise ships is included in the cruise price. Traditionally, the ships' restaurants organize two dinner services per day, early dining and late dining, and passengers are allocated a set dining time for the entire cruise; a recent trend is to allow diners to dine whenever they want. Having two dinner times allows the ship to have enough time and space to accommodate all of its guests. Having two different dinner services can cause some conflicts with some of the ship's events (such as shows and performances) for the late diners, but this problem is usually fixed by having a shorter version of the event take place before late dinner. Cunard Line ships maintain the class tradition of ocean liners and have separate dining rooms for different types of suites, while Celebrity Cruises and Princess Cruises have a standard dining room and "upgrade" specialty restaurants that require pre-booking and cover charges. Many cruises schedule one or more "formal dining" nights. Guests dress "formally", however, that is defined for the ship, often suits and ties or even tuxedos for men, and formal dresses for women. The menu is more upscale than usual.
Besides the dining room, modern cruise ships often contain one or more casual buffet-style eateries, which may be open 24 hours and with menus that vary throughout the day to provide meals ranging from breakfast to late-night snacks. In recent years, cruise lines have started to include a diverse range of ethnically themed restaurants aboard each ship. Ships also feature numerous bars and nightclubs for passenger entertainment; the majority of cruise lines do not include alcoholic beverages in their fares and passengers are expected to pay for drinks as they consume them. Most cruise lines also prohibit passengers from bringing aboard and consuming their own beverages, including alcohol, while aboard. Alcohol purchased duty-free is sealed and returned to passengers when they disembark.
There is often a central galley responsible for serving all major restaurants aboard the ship, though specialty restaurants may have their own separate galleys.
As with any vessel, adequate provisioning is crucial, especially on a cruise ship serving several thousand meals at each seating. For example, a quasi "military operation" is required to load and unload 3,600 passengers and eight tons of food at the beginning and end of each cruise, for the . | Cruise ship | Wikipedia | 466 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Other on-board facilities
Modern cruise ships typically have aboard some or all of the following facilities:
Buffet restaurant
Card room
Casino – Only open when the ship is at sea to avoid conflict with local laws
Child care facilities
Cinema
Clubs
Fitness center
Hot tub
Indoor and/or outdoor swimming pool with water slides
Infirmary and morgue
Karaoke
Library
Lounges
Observation lounge
Ping pong tables
Pool tables
Shops – Only open when the ship is at sea to avoid merchandising licensing and local taxes
Spa
Teen Lounges
Theatre with Broadway-style shows
Some ships have bowling alleys, ice skating rinks, rock climbing walls, sky-diving simulators, miniature golf courses, video arcades, ziplines, surfing simulators, water slides, basketball courts, tennis courts, chain restaurants, ropes obstacle courses, and even roller coasters.
Crew
Crew are usually hired on three to eleven month contracts which may then be renewed as mutually agreed, depending on service ratings from passengers as well as the cyclical nature of the cruise line operator. Most staff work 77-hour work weeks for 10 months continuously followed by two months of vacation.
There are no paid vacations or pensions for service, non-management crew, depending on the level of the position and the type of the contract. Non-service and management crew members get paid vacation, medical, retirement options, and can participate in the company's group insurance plan.
The direct salary is low by North American standards, though restaurant staff have considerable earning potential from passenger tips. Crew members do not have any expenses while on board, because food and accommodation, medical care, and transportation for most employees, are included. Bard College at Simon's Rock professor Francisca Oyogoa states that "Crewing agencies often exploit the desperation of potential employees."
Living arrangements vary by cruise line, but mostly by shipboard position. In general two employees share a cabin with a shower, commode and a desk with a television set, while senior officers are assigned single cabins. There is a set of facilities for the crew separate from that for passengers, such as mess rooms and bars, recreation rooms, prayer rooms/mosques, and fitness center, with some larger ships even having a crew deck with a swimming pool and hot tubs.
The International Labour Organization's 2006 Maritime Labour Convention is also known as the "Seafarers' Bill of Rights". | Cruise ship | Wikipedia | 479 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Business model
Most cruise lines since the 2000s have to some extent priced the cruising experience à la carte, as passenger spending aboard generates significantly more than ticket sales. The passenger's ticket includes the stateroom accommodation, room service, unlimited meals in the main dining room (or main restaurant) and buffet, access to shows, and use of pool and gym facilities, while there is a daily gratuity charge to cover housekeeping and waiter service. However, there are extra charges for alcohol and soft drinks, official cruise photos, Internet and wi-fi access, and specialty restaurants. Cruise lines earn significantly from selling onshore excursions offered by local contractors; keeping 50% or more of what passengers spend for these tours. In addition, cruise ships earn significant commissions on sales from onshore stores that are promoted on board as "preferred" (as much as 40% of gross sales). Facilitating this practice are modern cruise terminals with establishments of duty-free shops inside a perimeter accessible only by passengers and not by locals. Ports of call have often oriented their own businesses and facilities towards meeting the needs of visiting cruise ships. In one case, Icy Strait Point in Alaska, the entire destination was created explicitly and solely for cruise ship visitors.
On "cruises to nowhere" or "nowhere voyages", some cruise ships make two- to three-night round trips without visiting any ports of call.
Travel to and from the port of departure is usually the passengers' responsibility, although purchasing a transfer pass from the cruise line for the trip between the airport and cruise terminal will guarantee that the ship will not leave until the passenger is aboard. Similarly, if the passenger books a shore excursion with the cruise line and the tour runs late, the ship is obliged to remain until the passenger returns.
Luxury cruise lines such as Regent Seven Seas Cruises and Crystal Cruises market their fares as "all-inclusive". For example, the base fare on Regent Seven Seas ships includes most alcoholic beverages on board ship and most shore excursions in ports of call, as well as all gratuities that would normally be paid to hotel staff on the ship. The fare may also include a one-night hotel stay before boarding, and the air fare to and from the cruise's origin and destination ports.
Many cruise lines have loyalty programs. Using these and by booking inexpensive tickets, some people have found it cheaper to live continuously on cruise ships instead of on land. | Cruise ship | Wikipedia | 488 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Cruise ship utilization
Cruise ships and former liners sometimes find use in applications other than those for which they were built. Due to slower speed and reduced seaworthiness, as well as being largely introduced after several major wars, cruise ships have also been used as troop transport vessels. By contrast, ocean liners were often seen as the pride of their country and used to rival liners of other nations, and have been requisitioned during both World Wars and the Falklands War to transport soldiers and serve as hospital ships.
During the 1992 Summer Olympics, eleven cruise ships docked at the Port of Barcelona for an average of 18 days, served as floating hotels to help accommodate the large influx of visitors to the Games. They were available to sponsors and hosted 11,000 guests a day, making it the second largest concentration of Olympic accommodation behind the Olympic Village. This hosting solution has been used since then in Games held in coastal cities, such as at Sydney 2000, Athens 2004, London 2012, Sochi 2014, Rio 2016 and was going to be used at Tokyo 2020.
Cruise ships have been used to accommodate displaced persons during hurricanes. For example, on 1 September 2005, the U.S. Federal Emergency Management Agency (FEMA) contracted three Carnival Cruise Lines vessels (, the former , and the ) to house Hurricane Katrina evacuees. In 2017, cruise ships were used to help transport residents from some Caribbean islands destroyed by Hurricane Irma, as well as Puerto Rico residents displaced by Hurricane Maria.
The cruise ships have also been used for evacuations. In 2010, in response to the shutdown of UK airspace due to the eruption of Iceland's Eyjafjallajökull volcano, the newly completed was used to rescue 2,000 British tourists stranded in Spain as an act of goodwill by the owners. The ship departed from Southampton for Bilbao on 21 April, and returned on 23 April. A cruise ship was kept on standby in case inhabitants of Kangaroo Island required evacuation in 2020 after a series of fires burned on the island.
Regional industries
Most cruise ships sail the Caribbean or the Mediterranean. Others operate elsewhere in places like Alaska, the South Pacific, the Baltic Sea and New England. A cruise ship that is moving from one of these regions to another will commonly operate a repositioning cruise while doing so. Expedition cruise lines, which usually operate small ships, visit certain more specialized destinations such as the Arctic and Antarctica, or the Galápagos Islands. | Cruise ship | Wikipedia | 497 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
The number of cruise tourists worldwide in 2005 was estimated at some 14 million. The main region for cruising was North America (70% of cruises), where the Caribbean islands were the most popular destinations.
The second most popular region was continental Europe (13%), where the fastest growing segment is cruises in the Baltic Sea. The most visited Baltic ports are Copenhagen, St. Petersburg, Tallinn, Stockholm and Helsinki.
The seaport of St. Petersburg, the main Baltic port of call, received 426,500 passengers during the 2009 cruise season.
According to 2010 CEMAR statistics the Mediterranean cruise market is going through a fast and fundamental change; Italy has won prime position as a destination for European cruises, and destination for the whole of the Mediterranean basin. The most visited ports in Mediterranean Sea are Barcelona (Spain), Civitavecchia (Italy), Palma (Spain) and Venice (Italy).
2013 saw the entrance of the first Chinese company into the cruise market. China's first luxury cruise ship, Henna, made her maiden voyage from Sanya Phoenix Island International Port in late January.
Caribbean cruising industry
The Caribbean cruising industry is one of the largest in the world, responsible for over $2 billion in direct revenue to the Caribbean islands in 2012. Over 45,000 people from the Caribbean are directly employed in the cruise industry. An estimated 17,457,600 cruise passengers visited the islands in the 2011–2012 cruise year (May 2011 to April 2012.) Cruise lines operating in the Caribbean include Royal Caribbean International, Princess Cruises, Carnival Cruise Line, Celebrity Cruises, Disney Cruise Line, Holland America, P&O, Cunard and Norwegian Cruise Line. There are also smaller cruise lines that cater to a more intimate feeling among their guests. The three largest cruise operators are Carnival Corporation, Royal Caribbean International, and Star Cruises/Norwegian Cruise Lines.
Many American cruise lines to the Caribbean depart out of the Port of Miami, with "nearly one-third of the cruises sailing out of Miami in recent years". Other cruise ships depart from Port Everglades (in Fort Lauderdale), Port Canaveral (approximately east of Orlando), New York, Tampa, Galveston, New Orleans, Cape Liberty, Baltimore, Jacksonville, Charleston, Norfolk, Mobile, and San Juan, Puerto Rico. Some UK cruise lines base their ships out of Barbados for the Caribbean season, operating direct charter flights out of the UK.
The busiest ports of call in the Caribbean for cruising in the 2014 year are listed below: | Cruise ship | Wikipedia | 507 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Alaskan cruising industry
2016 was the most recent year of CLIA (Cruise Lines International Association) studies conducted around the cruise industry specifically in the US and more specifically Alaska. In 2016, Alaskan cruises generated nearly 5 million passenger and crew visits, 20.3% of all passenger and crew visits in the US. (NASDAQ, 2017) Cruise lines frequently bring passengers to Glacier Bay National Park, Ketchikan, Anchorage, Skagway, and the state's capital, Juneau.
Visitor volume is represented by overall visitors entering Alaskan waters and/or airspace. Between October 2016 and September 2017 Alaska had about 2.2 million visitors; 49% of those were through the cruise industry. That 2.2 million was a 27% increase since 2009, and the volume overall has steadily increased. Visitors generally spend money when travelling, and this is measured in two distinct areas: the cruising companies themselves and the visitors. There are no current numbers for cruise specific passenger spending ashore, but the overall visitor expenditure can be measured. Tours accounted for $394 million (18%), gifts and souvenirs $427 million (20%), food $428 million (20%), transportation $258 million (12%), lodging $454 million (21%), and other $217 million (10%). The second main area of economic growth comes from what the cruising companies and their crews spend themselves. Cruise liners spend around $297 million on the items that come in their packages on board and ashore as parts of group tours: things like stagecoach rides and boat tours on smaller vessels throughout their ports of call. This money is paid to the service providers by the cruise line company. Cruise liner crew are also a revenue generator, with 27,000 crew members visiting Alaska in 2017 alone, generating about $22 million. 2017 was also a good year for job generation within Alaska: 43,300 jobs were created, bringing in $1.5 billion in labor costs, and a total income of $4.5 billion was generated. These jobs were scattered across all of Alaska. Southeast Alaska had 11,925 jobs ($455 million labor income), Southwest 1,800 jobs ($50 million labor income), South Central 20,700 jobs ($761 million Labor income), Interior 8,500 jobs ($276 million labor income), Far North 375 jobs ($13 M labor income). Labor income is shown in the graph below.
Shipyards | Cruise ship | Wikipedia | 509 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
The construction market for cruise ships is dominated by three European companies and one Asian company:
Chantiers de l’Atlantique of France.
Fincantieri of Italy with:
Ancona shipyards (located at Ancona)
Marghera shipyards (located at Marghera, Venice)
Monfalcone shipyards (located at Monfalcone, Gorizia)
Sestri Ponente shipyards (located at Genoa)
VARD Braila shipyards (located at Braila)
VARD Søviknes Shipyard (located in Norway)
VARD Tulcea shipyards (located at Tulcea)
Meyer Werft of Germany with two shipyards:
Meyer Turku at Perno shipyard in Turku, Finland
Meyer Werft of Germany.
Mitsubishi Heavy Industries of Japan.
, 54 new ships have been ordered and are due to be delivered by 2028.
As of August 2024, there are 62 ships on order until 2036, adding 154,146 berths.
Safety and security
Piracy
As most of the passengers on a cruise are affluent and have considerable ransom potential, not to mention a considerable amount of cash and jewelry on board (for example in casinos and shops), there have been several high-profile pirate attacks on cruise ships, such as on and .
As a result, cruise ships have implemented various security measures. While most merchant shipping firms have generally avoided arming crew or security guards for reasons of safety, liability and conformity with the laws of the countries where they dock, cruise ships have small arms (usually semi-automatic pistols) stored in a safe accessible only by the captain who distributes them to authorized personnel such as security or the master-at-arms. The ship's high-pressure fire hoses can be used to keep boarders at bay, and often the vessel itself can be maneuvered to ram pirate craft. A recent technology to deter pirates has been the LRAD or sonic cannon which was used in the successful defence of Seabourn Spirit.
A related risk is that of terrorism, the most notable incident being that of the 1985 hijacking of Achille Lauro, an Italian cruise ship. | Cruise ship | Wikipedia | 441 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Crime on-board
Passengers entering the cruise ship are screened by metal detectors. Explosive detection machines used include X-ray machines and explosives trace-detection portal machines (a.k.a. "puffer machines"), to prevent weapons, drugs and other contraband on board. Security has been considerably tightened since 11 September 2001, such that these measures are similar to airport security.
In addition to security checkpoints, passengers are often given a ship-specific identification card, which must be shown in order to get on or off the ship. This prevents people boarding who are not entitled to do so, and also ensures the ship's crew are aware of who is on the ship. The Cruise Ship ID cards are also used as the passenger's room key. CCTV cameras are mounted frequently throughout the ship.
In 2010, the United States Congress passed the Cruise Vessel Security and Safety Act after numerous incidents of sexual violence, passenger disappearances, physical assault, and other serious crimes. Congress said:
Passengers on cruise vessels have an inadequate appreciation of their potential vulnerability to crime while on ocean voyages, and those who may be victimized lack the information they need to understand their legal rights or to know whom to contact for help in the immediate aftermath of the crime.
Congress said both passengers and crew committed crimes. It said data on the problem was lacking because cruise lines did not make it publicly available, multiple countries were involved in investigating incidents on international waters, and crime scenes could not be secured quickly by police. It recommended that owners of cruise vessels:
install acoustic hailing and warning devices capable of working at a distance.
install more security cameras
install peep holes in passenger room doors
limit access to passenger rooms to select staff at specific times
After investigating the death of Dianne Brimble in 2002, a coroner in Australia recommended:
Federal police officers travel on ships to ensure a quick response to crime,
scanners and drug detection dogs check passengers and crew at Australian ports,
an end to overlaps between jurisdictions, and
flags of ships be disregarded for nations unable to investigate incidents thoroughly and competently.
The lobby group International Cruise Victims Association, based in Arizona, pushes for more regulation of the cruise industry, and supports victims of crimes committed on cruise ships. | Cruise ship | Wikipedia | 451 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Overboard drownings
Passengers and crew sometimes drown after going overboard in what the industry calls man-overboard incidents (MOBs). From 2000 to 2018 more than 300 people fell off cruise ships or large ferries, which is an average of about 1.5 people each month. Of those, only about 17 to 25 percent were rescued. Critics of the industry blame alcohol promotion for many passenger deaths, and poor labour conditions for crew suicides. They also point to underinvestment in the latest MOB sensors, a lack of regulation and consumer protection, and a lack of on-board counselling services for crew. The industry blames irresponsible behaviour by passengers, and says overboard sensors are unreliable and generate false alarms.
Maritime lawyer Jim Walker estimates about half of all disappearances at sea involve some factor of foul play, and that a lack of police jurisdiction on international waters allows sexual predators to go unpunished.
Stability
Modern cruise ships are tall but remain stable due to their relatively low center of mass. This is due to large open spaces and the extensive use of aluminium, high-strength steel and other lightweight materials in the upper parts, and the fact that the heaviest components—engines, propellers, fuel tanks and such—are located at the bottom of the hull. Thus, even though modern cruise ships may appear tall, proper weight distribution ensures that they are not top-heavy. Furthermore, large cruise ships tend to be very wide, which considerably increases their initial stability by increasing the metacentric height.
Although most passenger ships utilize stabilizers to reduce rolling in heavy weather, they are only used for crew and passenger comfort and do not contribute to the overall intact stability of the vessel. The ships must fulfill all stability requirements even with the stabilizer fins retracted.
According to the Washington Post, a recent study by economic consultant G.P. Wild – commissioned by the cruise industry's trade group and released in March 2019 – argued that cruises are getting safer over time. The study claims that, even as capacity increased 55 percent between 2009 and 2018, the number of overall "operational incidents" declined 37 percent and the rate of man-overboard cases dropped 35 percent.
Disease
Norovirus
Norovirus is a virus that commonly causes gastroenteritis, and is also a cause of gastroenteritis on cruise ships. It is typically transmitted from person to person. Symptoms usually last between 1 and 3 days and generally resolve without treatment or long term consequences. The incubation period of the virus averages about 24 hours. | Cruise ship | Wikipedia | 506 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Norovirus outbreaks are often perceived to be associated with cruise ships. According to the United States CDC, the factors that cause norovirus to be associated with cruise ships include the closer tracking and faster reporting of illnesses on cruise ships compared to those on land; the closer living quarters that increases the amount of interpersonal contact; as well as the turnover of passengers that may bring the viruses on board.
However, the estimated likelihood of contracting gastroenteritis from any cause on an average 7-day cruise is less than 1%. In 2009, during which more than 13 million people took a cruise, there were nine reported norovirus outbreaks on cruise ships. Outbreak investigations by the United States Centers for Disease Control and Prevention (CDC) have shown that transmission among cruise ship passengers is primarily person-to-person; potable water supplies have not been implicated. In a study published in the Journal of the American Medical Association, the CDC reported that, "Perceptions that cruise ships can be luxury breeding grounds for acute gastroenteritis outbreaks don't hold water. A recent CDC report showed that from 2008 to 2014, only 0.18% of more than 73 million cruise passengers and 0.15% of some 28 million crew members reported symptoms of the illness."
Ships docked in port undergo surprise health inspections. In 2009, ships that underwent unannounced inspections by the CDC received an average CDC Vessel Sanitation Program score of approximately 97 out of a total possible 100 points. The minimum passing inspection score is 85. Collaboration with the CDC's Vessel Sanitation Program and the development of Outbreak Prevention and Response Plans has been credited in decreasing the incidence of norovirus outbreaks on ships.
Legionnaires' disease
Other pathogens which can colonise pools and spas including those on cruise ships include Legionella, the bacterium which causes Legionnaires' disease. Legionella, and in particular the most virulent strain, Legionella pneumophila serogroup 1, can cause infections when inhaled as an aerosol or aspirated. Individuals who are immunocompromised and those with pre-existing chronic respiratory and cardiac disease are more susceptible. Legionnaires' has been infrequently associated with cruise ships. | Cruise ship | Wikipedia | 456 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Enterotoxigenic Escherichia coli (ETEC)
Enterotoxigenic Escherichia coli is a form of E. coli and the leading bacterial cause of diarrhea in the developing world, as well as the most common cause of diarrhea for travelers to those areas. Since 2008 there has been at least one reported incident each year of E. coli on international cruise ships reported to the Vessel Sanitation Program of the Centers for Disease Control, though there were none in 2015. Causes of E. coli infection include the consumption of contaminated food or water contaminated by human waste.
COVID-19
News outlets reported several cases and suspected cases of Coronavirus disease 2019 associated with cruise ships in early 2020. Authorities variously turned away ships or quarantined them; cruise operators cancelled some port visits and ultimately suspended global cruise operations. People aboard cruise ships played a role in spreading the disease in some countries.
Environmental impact
Cruise ships generate a number of waste streams that can result in discharges to the marine environment, including sewage, graywater, hazardous wastes, oily bilge water, ballast water, and solid waste. They also emit air pollutants to the air and water. These wastes, if not properly treated and disposed of, can be a significant source of pathogens, nutrients, and toxic substances with the potential to threaten human health and damage aquatic life.
Most cruise ships run (primarily) on heavy fuel oil (HFO), or "bunker fuel", which, because of its high sulphur content, results in sulphur dioxide emissions worse than those of equivalent road traffic. The international MARPOL IV-14 agreement for Sulphur Emission Control Areas requires that cruise ships must use fuel containing no more than 0.10% sulphur or make use of exhaust gas scrubbers to reduce sulfur oxide emissions to no worse than an engine running on <0.1% sulfur fuel. Cruise ships may use 60 percent of the fuel energy for propulsion, and 40 percent for hotel functions, but loads and distribution depend highly on conditions.
It has been claimed that air pollution from maritime transport, including cruise ships, is responsible for 50,000 deaths per year in Europe.
Some cruise lines, such as Cunard, are taking steps to reduce environmental impact by refraining from discharges (Queen Mary 2 has a zero-discharge policy) and reducing their carbon dioxide output every year. | Cruise ship | Wikipedia | 488 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Cruise ships require electrical power, normally provided by diesel generators, although an increasing number of new ships are fueled by liquified natural gas (LNG). When docked, ships must run their generators continuously to power on-board facilities, unless they are capable of using onshore power, where available. Some cruise ships already support the use of shore power, while others are being adapted to do so.
Overtourism
Large cruise ships have been identified as one of the major causes of overtourism in places like Venice, Barcelona, and Dubrovnik.
Critics of the industry say it overwhelms the cities' infrastructure, causing overcrowding, damaging heritage sites, and changing the character of local neighbourhoods – as residential amenities and shops are replaced by tourist cafes and souvenir stands.
Cruise tourists contribute little economically to the places they visit. In Venice, short stay day trippers – including cruise tourists – account for 73% of all visitors, yet only contribute to 18% of the tourism economy. By contrast overnight visitors contribute 50%.
In Venice, campaigners have long been calling for a ban on large cruise ships entering the historic portion of the city. In 2021, they were successful. Ships weighing over 25,000 tonnes were banned from entering the Venice Lagoon along the Giudecca Canal in an attempt to protect the fragile lagoon ecosystem and to limit the damage to the underwater foundations of the city's historic centre. At the time, UNESCO warned the city could be placed on its endangered list if ships were not diverted to another port.
In 2023, Barcelona Mayor, Ada Colau, spoke out in favour of limiting the number of cruise ships arriving in the city. Currently up to 200,000 people disembark each month in peak season, Colau's new measures could halve this. In a 2019 study by Transport and Environment, Barcelona ranked as the worst cruise port for air pollution in Europe.
From 2024, only 1,000 cruise passengers per day will be allowed to disembark in Bar Harbor, Maine, United States. The average cruise ship holds 3,000 passengers. The move came after a 2021 survey showed the majority of local residents were unhappy with large cruise ships, and felt that the town was overrun by cruise tourists.
Sunken vessels | Cruise ship | Wikipedia | 461 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
: caught fire and sank on 24 October 1961, one dead.
: caught fire and sank on 11 October 1980, with no fatalities.
: accidentally hit a rock 16 February 1986, one dead.
: sank on 21 October 1988 after accidentally colliding with the cargo ship Adige, 4 dead.
: accidentally sunk on 4 August 1991 after suffering uncontrolled flooding, no fatalities.
: caught fire and sank 30 November 1994, two dead.
: caught fire and sank on May 21, 1999, with no fatalities.
: accidentally hit a reef on 30 April 2000, no fatalities.
: sank en route to the scrapyard on October 21, 2000, with no fatalities.
: sank on 17 December 2000 due to possible sabotage, with no fatalities.
: accidentally hit a reef and capsized on 6 April 2007, two dead.
: accidentally sunk on 23 November 2007 after hitting an iceberg, no fatalities.
: sank accidentally on 13 January 2012 after hitting some rocks, 32 dead. The wreck was salvaged three years after the incident and then towed to the port of Genoa, where it was scrapped.
: capsized and sank in a storm on June 1, 2015, killing 442 people.
: a river cruise ship, sank on 29 May 2019 after accidentally colliding with the river cruise ship Viking Sigyn, 28 dead. | Cruise ship | Wikipedia | 270 | 314855 | https://en.wikipedia.org/wiki/Cruise%20ship | Technology | Naval transport | null |
Oryx ( ) is a genus consisting of four large antelope species called oryxes. Their pelage is pale with contrasting dark markings in the face and on the legs, and their long horns are almost straight. The exception is the scimitar oryx, which lacks dark markings on the legs, only has faint dark markings on the head, has an ochre neck, and has horns that are clearly decurved.
The Arabian oryx was only saved from extinction through a captive-breeding program and reintroduction to the wild. The scimitar oryx, which was listed as extinct in the wild, also relied on a captive-breeding program for its survival.
Etymology
The term "oryx" comes from the Greek word ὄρυξ, óryx, for a type of antelope. The Greek plural form is óryges, although "oryxes" has been established in English. Herodotus mentions a type of gazelle in Libya called ὄρυς, orus, probably related to the verb ὀρύσσω, orussō, or ὀρύττω, oruttō, meaning "to dig". White oryxes are known to dig holes in the sand.
Species
Arabian oryx
The Arabian oryx (Oryx leucoryx, Arabic: المها), became extinct in the wild in 1972 in the Arabian Peninsula. It was reintroduced in 1982 in Oman, but poaching has reduced its numbers there. One of the largest populations of Arabian oryxes exists on Sir Bani Yas Island in the United Arab Emirates. Additional populations have been reintroduced in Qatar, Bahrain, Israel, Jordan, and Saudi Arabia. As of 2011, the total wild population is over 1,000, and 6,000–7,000 are being held in captivity. In 2011, the IUCN downgraded its threat category from extinct in the wild to vulnerable, the first species to have changed back in this way. | Oryx | Wikipedia | 410 | 314907 | https://en.wikipedia.org/wiki/Oryx | Biology and health sciences | Bovidae | Animals |
Scimitar oryx
The scimitar oryx, also called the scimitar-horned oryx (Oryx dammah), of North Africa used to be listed as extinct in the wild, but it is now declared as endangered. Unconfirmed surviving populations have been reported in central Niger and Chad, and a semi-wild population currently inhabiting a fenced nature reserve in Tunisia is being expanded for reintroduction to the wild in that country. Several thousand are held in captivity around the world.
East African oryx and gemsbok
The East African oryx (Oryx beisa) inhabits eastern Africa and the closely related gemsbok (Oryx gazella) inhabits southern Africa. The gemsbok is monotypic and the East African oryx has two subspecies; the common beisa oryx (O. b. beisa) and the fringe-eared oryx (O. b. callotis). In the past, both were considered subspecies of the gemsbok. The East African oryx is an endangered species, whereas the gemsbok is not.
Gemsbok were introduced in New Mexico by the Department of Game and Fish in the late 1960s and early 1970s as an experiment in offering a unique hunting opportunity to New Mexico residents. Between 1969 and 1973, 95 oryx were released onto White Sands Missile Range. White Sands Missile Range, located between the cities of Albuquerque, NM and El Paso, TX, is a 3,200 square mile US Army facility which also hosts White Sands National Park. Researchers believed that the population would never grow beyond 500 to 600 and would remain within the Tularosa Basin. However, the animals proved to be extremely opportunistic, and quickly spread into the San Andres Mountains to the north and west of Tularosa Basin. | Oryx | Wikipedia | 369 | 314907 | https://en.wikipedia.org/wiki/Oryx | Biology and health sciences | Bovidae | Animals |
At one time, numbers of oryx in New Mexico were estimated to be around 6,000 (original release numbers were less than 100). Today, numbers have been held around the 2,000 mark through managed hunting efforts. The success of the oryx in New Mexico is due in part to the abundance of food. In Africa, they eat grasses, forbs, and melons. In New Mexico, they feed on desert grasses, yucca, buffalo gourds, and mesquite bean pods. They are especially adapted to desert life and can go a long time without drinking water. This area also lacks a way to control the population. Lions and other natural predators cull the population in Africa, with only 10% of calves reaching one year of age. In New Mexico, predators like coyotes and mountain lions are not effective at controlling numbers, allowing the oryx to reproduce without restriction.
Classification
Family Bovidae
Subfamily Hippotraginae
Genus Oryx
Scimitar oryx, O. dammah
Gemsbok, O. gazella
East African oryx, O. beisa (formerly in O. gazella)
Common beisa oryx, O. b. beisa
Fringe-eared oryx, O. b. callotis
Arabian oryx, O. leucoryx
Ecology
All oryx species prefer near-desert conditions and can survive without water for long periods. They live in herds of up to 600 animals. Newborn calves are able to run with the herd immediately after birth. Both males and females possess permanent horns. The horns are narrow and straight except in the scimitar oryx, where they curve backwards like a scimitar. The horns can be lethal: oryxes have been known to kill lions with them, and they are thus sometimes called sabre antelopes (not to be confused with the sable antelope). The horns also make the animals a prized game trophy, which has led to the near-extinction of the two northern species.
As an introduced species
Between 1969 and 1977, the New Mexico Department of Game and Fish in the US intentionally released 95 gemsbok into its state's White Sands Missile Range and that population is now estimated between 3,000 and 6,000 animals. Within the state of New Mexico, oryxes are classified as "big game" and can be hunted. | Oryx | Wikipedia | 481 | 314907 | https://en.wikipedia.org/wiki/Oryx | Biology and health sciences | Bovidae | Animals |
Oryxes in popular culture
The oryx is the national animal of Namibia, the State of Qatar, and the company Qatar Airways has an oryx as its logo.
The main boss of the MMO game Realm of the Mad God is Oryx the Mad God, named after the creator of the original sprite sheets, Oryx. His four direct subordinates also bear the names of four South African species of oryx.
Oryxes appear briefly, along with many other species of animal, in the Talk Talk music video It's My Life.
In the video game Tom Clancy's Rainbow Six Siege, a playable defending operator nicknamed Oryx was introduced in Year 5 Season 1. His ability is called "Remah Dash," where he can charge to break holes in walls and knock down enemies.
Oryx is a nickname for a character in Margaret Atwood's book Oryx and Crake.
Oryx is also the main antagonist’s name in the video game Destiny: The Taken King, a god who seeks vengeance on the player, known as a Guardian, after they killed his son Crota. He is killed by the player in the raid "King’s Fall". He is portrayed as "Oryx, the Taken King".
The Oryx is mentioned in Pliny's Natural History, in which he writes, "There is a wild beast, named by the Egyptians Oryx, which, when the star [Sirius] rises, is said to stand opposite to it, to look steadfastly at it, and then to sneeze, as if it were worshiping it."
In the 1994 film and 2019 remake of The Lion King and The Lion King II: Simba's Pride, the two species of oryxes in Hell's Gate National Park are the East African oryx and gemsbok. | Oryx | Wikipedia | 378 | 314907 | https://en.wikipedia.org/wiki/Oryx | Biology and health sciences | Bovidae | Animals |
Myxozoa (etymology: Greek: μύξα myxa "slime" or "mucus" + thematic vowel o + ζῷον zoon "animal") is a subphylum of aquatic cnidarian animals – all obligate parasites. It contains the smallest animals ever known to have lived. Over 2,180 species have been described and some estimates have suggested at least 30,000 undiscovered species. Many have a two-host lifecycle, involving a fish and an annelid worm or a bryozoan. The average size of a myxosporean spore usually ranges from 10 μm to 20 μm, whereas that of a malacosporean (a subclade of the Myxozoa) spore can be up to 2 mm. Myxozoans can live in both freshwater and marine habitats.
Myxozoans are highly derived cnidarians that have undergone dramatic evolution from a free swimming, self-sufficient jellyfish-like creature into their current form of obligate parasites composed of very few cells. As myxozoans evolved into microscopic parasites, they lost many genes responsible for multicellular development, coordination, cell–cell communication, and even, in some cases, aerobic respiration. The genomes of some myxozoans are now among the smallest genomes of any known animal species.
Life cycle and pathology
Myxozoans are endoparasitic animals exhibiting complex life cycles that, in most of the documented cases, involve an intermediate host, usually a fish, but in rare cases amphibians, reptiles, birds, and mammals; and a definitive host, usually an annelid or an ectoproct. | Myxozoa | Wikipedia | 357 | 314911 | https://en.wikipedia.org/wiki/Myxozoa | Biology and health sciences | Cnidarians | Animals |
Only about 100 life cycles have been resolved and it is suspected that there may be some exclusively terrestrial. The mechanism of infection occurs through valve spores that have many forms, but their main morphology is the same: one or two sporoplasts, which are the real infectious agent, surrounded by a layer of flattened cells called valve cells, which can secrete a layer protective coating and form float appendages. Integrated into the layer of valve cells are two to four specialized capsulogenic cells (in a few cases, one or even 15), each carrying a polar capsule containing coiled polar filaments, an extrudable organelle used for recognition, contact and infiltration. Myxospores are ingested by annelids, in which the polar filaments extrude to anchor the spore to the gut epithelium. Opening of the shell valves allows the sporoplasms to penetrate into the epithelium. Subsequently, the parasite undergoes reproduction and development in the gut tissue, and finally produces usually eight actinosporean spore stages (actinospores) within a pansporocyst. After mature actinospores are released from their hosts they float in the water column. Upon contact with skin or gills of fish, sporoplasms penetrate through the epithelium, followed by development of the myxosporean stage. Myxosporean trophozoites are characterized by cell-in-cell state, where the secondary (daughter) cells develop in the mother (primary) cells. The presporogonic stages multiply, migrate via nervous or circulatory systems, and develop into sporogonic stages. At the final site of infection, they produce mature spores within mono- or di-sporic pseudoplasmodia, or poly-sporic plasmodia. | Myxozoa | Wikipedia | 388 | 314911 | https://en.wikipedia.org/wiki/Myxozoa | Biology and health sciences | Cnidarians | Animals |
Relationships between myxosporeans and their hosts are often highly evolved and do not usually result in severe diseases of the natural host. Infection in fish hosts can be extremely long-lasting, potentially persisting for the lifetime of the host. However, an increasing number of myxosporeans have become pathogens with significant impact to the commercial fish industry, largely as a result of aquaculture bringing new species into contact with myxosporeans to which they had not been previously exposed, and to which they are highly susceptible. The economic impact of such parasites can be severe, especially where prevalence rates are high; they may also have a severe impact on wild fish stocks.
The diseases caused by myxosporeas in cultured fish with the most significant economic impact worldwide are proliferative kidney disease (PKD) caused by the malacosporean T. bryosalmonae, and whirling disease, caused by a myxosporean M. cerebralis; both diseases affect salmon. Enteromyxosis is caused by E. leei in cultured marine sparids, while proliferative gill disease (or “hamburger disease”) is caused by H. ictaluri in catfish and S. renicola infections occur in common carp.
Anatomy
Myxozoans are very small animals, typically 10–300 μm in length.
Like other cnidarians they possess cnidocysts, which were referred to as "polar capsules" before the discovery that myxozoans are cnidarians. These cnidocysts fire tubules as in other cnidarians; some inject substances into the host. However, the tubules lack hooks or barbs, and in some species are more elastic than in other cnidarians. | Myxozoa | Wikipedia | 364 | 314911 | https://en.wikipedia.org/wiki/Myxozoa | Biology and health sciences | Cnidarians | Animals |
Myxozoans have secondarily lost epithelial structures, a nervous system, gut, and cilia. Most lack muscles, though these are retained in some members of malacosporea. Those who have lost their muscles move around inside the host using other forms of locomotion, such as the use of filopodia, spore valve contractions, amoeboid movements, and rapidly creating and reabsorbing folds on the cell membrane. Myxozoans do not undergo embryogenesis during development and have lost true gametes. Instead, they reproduce via multicellular spores. These spores contain the polar capsules, which are not typically present in somatic cells. Centrioles are not involved in the nuclear division of myxozoans. Cell division by binary fission is rare, and cells divide instead via endogeny.
In 2020, the myxozoan Henneguya salminicola was found to lack a mitochondrial genome, and thus be incapable of aerobic respiration; it was the first animal to be positively identified as such. Its actual metabolism is currently unknown.
Phylogenetics
Myxozoans were originally considered to be protozoans, and were included among other non-motile forms in the group Sporozoa. As their distinct nature became clear through 18S ribosomal DNA (rDNA) sequencing, they were relocated in the metazoa. Detailed classification within the metazoa was however long hindered by conflicting rDNA evidence: although 18S rDNA suggested an affinity with Cnidaria, other rDNA sampled, and the HOX genes of two species, were more similar to those of the Bilateria.
The discovery that Buddenbrockia plumatellae, a worm-like parasite of bryozoans up to 2 mm in length, is a myxozoan initially appeared to strengthen the case for a bilaterian origin, as the body plan is superficially similar. Nevertheless, closer examination reveals that Buddenbrockia longitudinal symmetry is not twofold, but fourfold, casting doubt on this hypothesis. | Myxozoa | Wikipedia | 434 | 314911 | https://en.wikipedia.org/wiki/Myxozoa | Biology and health sciences | Cnidarians | Animals |
Further testing resolved the genetic conundrum by sourcing the first three previously identified discrepant HOX genes (Myx1-3) to the bryozoan Cristatella mucedo and the fourth (Myx4) to northern pike, the respective hosts of the two corresponding Myxozoa samples. This explained the confusion: the original experiments had used samples contaminated by tissue from host organisms, leading to false positives for a position among the Bilateria. More careful cloning of 50 coding genes from Buddenbrockia firmly established the clade as severely modified members of the phylum Cnidaria, with medusozoans as their closest relatives. Similarities between myxozoan polar capsules and cnidarian nematocysts had been drawn for a long time, but were generally assumed to be the result of convergent evolution.
Taxonomists now recognize the outdated subgroup Actinosporea as a life-cycle phase of Myxosporea.
Molecular clocks suggest that myxozoans and their closest relatives, the polypodiozoa, shared their last common ancestor with medusazoans about 600 million years ago, during the Ediacaran period.
Taxonomy
Myxozoan taxonomy has undergone great and important changes in its levels of generic, family and suborder classification. Fiala et al. (2015) proposed a new classification based on spores. | Myxozoa | Wikipedia | 293 | 314911 | https://en.wikipedia.org/wiki/Myxozoa | Biology and health sciences | Cnidarians | Animals |
An aquatic animal is any animal, whether vertebrate or invertebrate, that lives in a body of water for all or most of its lifetime. Aquatic animals generally conduct gas exchange in water by extracting dissolved oxygen via specialised respiratory organs called gills, through the skin or across enteral mucosae, although some are evolved from terrestrial ancestors that re-adapted to aquatic environments (e.g. marine reptiles and marine mammals), in which case they actually use lungs to breathe air and are essentially holding their breath when living in water. Some species of gastropod mollusc, such as the eastern emerald sea slug, are even capable of kleptoplastic photosynthesis via endosymbiosis with ingested yellow-green algae.
Almost all aquatic animals reproduce in water, either oviparously or viviparously, and many species routinely migrate between different water bodies during their life cycle. Some animals have fully aquatic life stages (typically as eggs and larvae), while as adults they become terrestrial or semi-aquatic after undergoing metamorphosis. Such examples include amphibians such as frogs, many flying insects such as mosquitoes, mayflies, dragonflies, damselflies and caddisflies, as well as some species of cephalopod molluscs such as the algae octopus (whose larvae are completely planktonic, but adults are highly terrestrial).
Aquatic animals are a diverse polyphyletic group based purely on the natural environments they inhabit, and many morphological and behavioral similarities among them are the result of convergent evolution. They are distinct from terrestrial and semi-aquatic animals, who can survive away from water bodies, while aquatic animals often die of dehydration or hypoxia after prolonged removal out of water due to either gill failure or compressive asphyxia by their own body weight (as in the case of whale beaching). Along with aquatic plants, algae and microbes, aquatic animals form the food webs of various marine, brackish and freshwater aquatic ecosystems.
Description
The term aquatic can be applied to animals that live in either fresh water or salt water. However, the adjective marine is most commonly used for animals that live in saltwater or sometimes brackish water, i.e. in oceans, shallow seas, estuaries, etc. | Aquatic animal | Wikipedia | 470 | 314928 | https://en.wikipedia.org/wiki/Aquatic%20animal | Biology and health sciences | General classifications | Animals |
Aquatic animals can be separated into four main groups according to their positions within the water column.
Neustons ("floaters"), more specifically the zooneustons, inhabit the surface ecosystem and use buoyancy to stay at the water surface, sometimes with appendages hanging from the underside for foraging (e.g. Portuguese man o' war, chondrophores and the buoy barnacle). They only move around via passive locomotion, meaning they have vagility but no motility.
Planktons ("drifters"), more specifically the metazoan zooplanktons, are suspended within the water column with no motility (most aquatic larvae) or limited motility (e.g. jellyfish, salps, larvaceans, and escape responses of copepods), causing them to be mostly carried by the water currents.
Nektons ("swimmers") have active motility that are strong enough to propel and overcome the influence of water currents. These are the aquatic animals most familiar to the common knowledge, as their movements are obvious on the macroscopic scale and the cultivation and harvesting of their biomass is most important to humans as seafoods. Nektons often have powerful tails, paddle/fan-shaped appendages with large wetted surfaces (e.g. fins, flippers or webbed feet) and/or jet propulsion (in the case of cephalopods) to achieve aquatic locomotion. | Aquatic animal | Wikipedia | 307 | 314928 | https://en.wikipedia.org/wiki/Aquatic%20animal | Biology and health sciences | General classifications | Animals |
Benthos ("bottom dwellers") inhabit the benthic zone at the floor of water bodies, which include both shallow sea (coastal, littoral and neritic) and deep sea communities. These animals include sessile organisms (e.g. sponges, sea anemones, corals, sea pens, sea lilies and sea squirts, some of which are reef-builders crucial to the biodiversity of marine ecosystems), sedentary filter feeders (e.g. bivalve molluscs) and ambush predators (e.g. flatfishes and bobbit worms, who often burrow or camouflage within the marine sediment), and more actively moving bottom feeders who swim (e.g. demersal fishes) and crawl around (e.g. decapod crustaceans, marine chelicerates, octopus, most non-bivalvian molluscs, echinoderms etc.). Many benthic animals are algivores, detrivores and scavengers who are important basal consumers and intermediate recyclers in the marine nitrogen cycle. | Aquatic animal | Wikipedia | 233 | 314928 | https://en.wikipedia.org/wiki/Aquatic%20animal | Biology and health sciences | General classifications | Animals |
Aquatic animals (especially freshwater animals) are often of special concern to conservationists because of the fragility of their environments. Aquatic animals are subject to pressure from overfishing/hunting, destructive fishing, water pollution, acidification, climate change and competition from invasive species. Many aquatic ecosystems are at risk of habitat destruction/fragmentation, which puts aquatic animals at risk as well. Aquatic animals play an important role in the world. The biodiversity of aquatic animals provide food, energy, and even jobs.
Freshwater aquatic animals
Fresh water creates a hypotonic environment for aquatic organisms. This is problematic for organisms with pervious skins and gills, whose cell membranes may rupture if excess water is not excreted. Some protists accomplish this using contractile vacuoles, while freshwater fish excrete excess water via the kidney. Although most aquatic organisms have a limited ability to regulate their osmotic balance and therefore can only live within a narrow range of salinity, diadromous fish have the ability to migrate between fresh and saline water bodies. During these migrations they undergo changes to adapt to the surroundings of the changed salinities; these processes are hormonally controlled. The European eel (Anguilla anguilla) uses the hormone prolactin, while in salmon (Salmo salar) the hormone cortisol plays a key role during this process.
Freshwater molluscs include freshwater snails and freshwater bivalves. Freshwater crustaceans include freshwater shrimps, crabs, crayfish,freshwater pirahnas and copepods. | Aquatic animal | Wikipedia | 319 | 314928 | https://en.wikipedia.org/wiki/Aquatic%20animal | Biology and health sciences | General classifications | Animals |
Air-breathing aquatic animals
In addition to water-breathing animals (e.g. fish, most molluscs, etc.), the term "aquatic animal" can be applied to air-breathing tetrapods who have evolved for aquatic life. The most proliferative extant group are the marine mammals, such as Cetacea (whales, dolphins and porpoises, with some freshwater species) and Sirenia (dugongs and manatees), who are too evolved for aquatic life to survive on land at all (where they will die of beaching), as well as the highly aquatically adapted but land-dwelling pinnipeds (true seals, eared seals and the walrus). The term "aquatic mammal" is also applied to riparian mammals like the river otter (Lontra canadensis) and beavers (family Castoridae), although they are technically semiaquatic or amphibious. Unlike the more common gill-bearing aquatic animals, these air-breathing animals have lungs (which are homologous to the swim bladders in bony fish) and need to surface periodically to change breaths, but their ranges are not restricted by oxygen saturation in water, although salinity changes can still affect their physiology to an extent.
There are also reptilian animals that are highly evolved for life in water, although most extant aquatic reptiles, including crocodilians, turtles, water snakes and the marine iguana, are technically semi-aquatic rather than fully aquatic, and most of them only inhabit freshwater ecosystems. Marine reptiles were once a dominant group of ocean predators that altered the marine fauna during the Mesozoic, although most of them died out during the Cretaceous-Paleogene extinction event and now only the sea turtles (the only remaining descendants of the Mesozoic marine reptiles) and sea snakes (which only evolved during the Cenozoic) remain fully aquatic in saltwater ecosystems. | Aquatic animal | Wikipedia | 398 | 314928 | https://en.wikipedia.org/wiki/Aquatic%20animal | Biology and health sciences | General classifications | Animals |
Amphibians, while still requiring access to water to inhabit, are separated into their own ecological classification. The majority of amphibians — except the order Gymnophiona (caecilians), which are mainly terrestrial burrowers — have a fully aquatic larval form known as tadpoles, but those from the order Anura (frogs and toads) and some of the order Urodela (salamanders) will metamorphosize into lung-bearing and sometimes skin-breathing terrestrial adults, and most of them may return to the water to breed. Axolotl, a Mexican salamander that retains its larval external gills into adulthood, is the only extant amphibian that remains fully aquatic throughout the entire life cycle.
Certain amphibious fish also evolved to breathe air to survive oxygen-deprived waters, such as lungfishes, mudskippers, labyrinth fishes, bichirs, arapaima and walking catfish. Their abilities to breathe atmospheric oxygen are achieved via skin-breathing, enteral respiration, or specialized gill organs such as the labyrinth organ and even primitive lungs (lungfish and bichirs).
Most molluscs have gills, while some freshwater gastropods (e.g. Planorbidae) have evolved pallial lungs and some amphibious species (e.g. Ampullariidae) have both. Many species of octopus have cutaneous respiration that allows them to survive out of water at the intertidal zones, with at least one species (Abdopus aculeatus) being routinely terrestrial hunting crabs among the tidal pools of rocky shores.
Importance
Environmental
Aquatic animals play an important role for the environment as indicator species, as they are particularly sensitive to deterioration in water quality and climate change. Biodiversity of aquatic animals is also an important factor for the sustainability of aquatic ecosystems as it reflects the food web status and the carrying capacity of the local habitats. Many migratory aquatic animals, predominantly forage fish (such as sardines) and euryhaline fish (such as salmon), are keystone species that accumulate and transfer biomass between marine, freshwater and even to terrestrial ecosystems.
Importance to humans | Aquatic animal | Wikipedia | 438 | 314928 | https://en.wikipedia.org/wiki/Aquatic%20animal | Biology and health sciences | General classifications | Animals |
As a food source
Aquatic animals are important to humans as a source of food (i.e. seafood) and as raw material for fodders (e.g. feeder fish and fish meal), pharmaceuticals (e.g. fish oil, krill oil, cytarabine and bryostatin) and various industrial chemicals (e.g. chitin and bioplastics, formerly also whale oil). The harvesting of aquatic animals, especially finfish, shellfish and inkfish, provides direct and indirect employment to the livelihood of over 500 million people in developing countries, and both the fishing industry and aquaculture make up a major component of the primary sector of the economy.
The United Nations Food and Agriculture Organization estimates that global consumption of aquatic animals in 2022 was 185 million tonnes (live weight equivalent), an increase of 4 percent from 2020. The value of the 2022 global trade was estimated at USD 452 billion, comprising USD 157 billion for wild fisheries and USD 296 billion for aquaculture. Of the total 185 million tonnes of aquatic animals produced in 2022, about 164.6 million tonnes (89%) were destined for human consumption, equivalent to an estimated 20.7 kg per capita. The remaining 20.8 million tonnes were destined for non-food uses, to produce mainly fishmeal and fish oil. In 2022, China remained the major producer (36% of the total), followed by India (8%), Indonesia (7%), Vietnam (5%) and Peru (3%).
Total fish production in 2016 reached an all-time high of 171 million tonnes, of which 88% was utilized for direct human consumption, resulting in a record-high per capita consumption of . Since 1961 the annual global growth in fish consumption has been twice as high as population growth. While annual growth of aquaculture has declined in recent years, significant double-digit growth is still recorded in some countries, particularly in Africa and Asia. Overfishing and destructive fishing practices fuelled by commercial incentives have reduced fish stocks beyond sustainable levels in many world regions, causing the fishery industry to maladaptively fishing down the food web. It was estimated in 2014 that global fisheries were adding US$270 billion a year to global GDP, but by full implementation of sustainable fishing, that figure could rise by as much as US$50 billion. UN Food and Agriculture Organization projects world production of aquatic animals to reach 205 million tonnes by 2032. | Aquatic animal | Wikipedia | 502 | 314928 | https://en.wikipedia.org/wiki/Aquatic%20animal | Biology and health sciences | General classifications | Animals |
Where sex-disaggregated data are available, approximately 24 percent of the total workforce were women; of these, 53 percent were employed in the sector on a full-time basis, a great improvement since 1995, when only 32 percent of women were employed full time.
Aquatic animal are highly perishable and several chemical and biological changes take place immediately after death; this can result in spoilage and food safety risks if good handling and preservation practices are not applied all along the supply chain. These practices are based on temperature reduction (chilling and freezing), heat treatment (canning, boiling and smoking), reduction of available water (drying, salting and smoking) and changing of the storage environment (vacuum packing, modified atmosphere packaging and refrigeration). Aquatic animal products also require special facilities such as cold storage and refrigerated transport, and rapid delivery to consumers.
Recreational fishing
In addition to commercial and subsistence fishing, recreational fishing is a popular pastime in both developed and developing countries, and the manufacturing, retail and service sectors associated with recreational fishing have together conglomerated into a multibillion-dollar industry. In 2014 alone, around 11 million saltwater sportfishing participants the United States generated USD$58 billion of retail revenue (comparatively, commercial fishing generated USD$141 billion that same year). In 2021, the total revenue of recreational fishing industry in the United States overtook those of Lockheed Martin, Intel, Chrysler and Google; and together with personnel salary (about USD$39.5 billion) and various tolls and fees collected by fisheries management agencies (about USD$17 billion), contributed almost USD$129 billion to the GDP of the United States, roughly 1% of the national GDP and more than the economic sum of 17 U.S. states. | Aquatic animal | Wikipedia | 361 | 314928 | https://en.wikipedia.org/wiki/Aquatic%20animal | Biology and health sciences | General classifications | Animals |
Yellowjacket or yellowjacket is the common name in North America for predatory social wasps of the genera Vespula and Dolichovespula. Members of these genera are known simply as "wasps" in other English-speaking countries. Most of these are black and yellow like the eastern yellowjacket (Vespula maculifrons) and the aerial yellowjacket (Dolichovespula arenaria); some are black and white like the bald-faced hornet (Dolichovespula maculata). Some have an abdomen with a red background color instead of black. They can be identified by their distinctive markings, their occurrence only in colonies, and a characteristic, rapid, side-to-side flight pattern prior to landing. All females are capable of stinging. Yellowjackets are important predators of pest insects.
Identification
Yellowjackets may be confused with other wasps, such as hornets and paper wasps such as Polistes dominula. A typical yellowjacket worker is about long, with alternating bands on the abdomen; the queen is larger, about long (the different patterns on their abdomens help separate various species).
Yellowjackets are sometimes mistakenly called "bees" (as in "meat bees"), given that they are similar in size and general coloration to honey bees. In contrast to honey bees, yellowjackets have yellow or white markings, are not covered with tan-brown dense hair on their bodies, and do not have the flattened, hairy pollen-carrying hind legs characteristic of honey bees (although they are capable of pollination). | Yellowjacket | Wikipedia | 322 | 314968 | https://en.wikipedia.org/wiki/Yellowjacket | Biology and health sciences | Hymenoptera | Animals |
Yellowjackets have lance-like stingers with small barbs, and typically sting repeatedly, though occasionally a stinger becomes lodged and pulls free of the wasp's body; the venom, like most bee and wasp venoms, is primarily dangerous to only those humans who are allergic or are stung many times. All species have yellow or white on their faces. Their mouthparts are well-developed with strong mandibles for capturing and chewing insects, with probosces for sucking nectar, fruit, and other juices. Yellowjackets build nests in trees, shrubs, or in protected places such as inside man-made structures, or in soil cavities, tree stumps, mouse burrows, etc. They build them from wood fiber they chew into a paper-like pulp. Many other insects exhibit protective mimicry of aggressive, stinging yellowjackets; in addition to numerous bees and wasps (Müllerian mimicry), the list includes some flies, moths, and beetles (Batesian mimicry).
Yellowjackets' closest relatives, the hornets, closely resemble them but have larger heads, seen especially in the large distance from the eyes to the back of the head.
Life cycle and habits
Yellowjackets are social hunters living in colonies containing workers, queens, and males (drones). Colonies are annual with only inseminated queens overwintering. Fertilized queens are found in protected places such as in hollow logs, stumps, under bark, leaf litter, soil cavities, and man-made structures. Queens emerge during the warm days of late spring or early summer, select a nest site, and build a small paper nest in which they lay eggs. After eggs hatch from the 30 to 50 brood cells, the queen feeds the young larvae for about 18 to 20 days. Larvae pupate, then emerge later as small, infertile females called workers. Workers in the colony take over caring for the larvae, feeding them with chewed-up meat or fruit. By midsummer, the first adult workers emerge and assume the tasks of nest expansion, foraging for food, care of the queen and larvae, and colony defense. | Yellowjacket | Wikipedia | 434 | 314968 | https://en.wikipedia.org/wiki/Yellowjacket | Biology and health sciences | Hymenoptera | Animals |
From this time until her death in the autumn, the queen remains inside the nest, laying eggs. The colony then expands rapidly, reaching a maximum size of 4,000–5,000 workers and a nest of 10,000–15,000 cells in late summer. The species V. squamosa, in the southern part of its range, may build much larger perennial colonies populated by dozens of queens, tens of thousands of workers, and hundreds of thousands of cells. At peak size, reproductive cells are built with new males and queens produced. Adult reproductives remain in the nest fed by the workers. New queens build up fat reserves to overwinter. Adult reproductives leave the parent colony to mate. After mating, males quickly die, while fertilized queens seek protected places to overwinter. Parent colony workers dwindle, usually leaving the nest to die, as does the founding queen. Abandoned nests rapidly decompose and disintegrate during the winter. They can persist as long as they are kept dry, but are rarely used again. In the spring, the cycle is repeated; weather in the spring is the most important factor in colony establishment.
The adult yellowjacket diet consists primarily of sugars and carbohydrates, such as fruits, flower nectar, and tree sap. Larvae feed on proteins derived from insects, meats, and fish. Workers collect, chew, and condition such foods before feeding them to the larvae. Many of the insects collected by the workers are considered pest species, making the yellowjacket beneficial to agriculture. Larvae, in return, secrete a sugary substance for workers to eat; this exchange is a form of trophallaxis. As insect sources of food diminish in late summer, larvae produce less for workers to eat. Foraging workers pursue sources of sugar outside the nest including ripe fruits and human garbage. | Yellowjacket | Wikipedia | 384 | 314968 | https://en.wikipedia.org/wiki/Yellowjacket | Biology and health sciences | Hymenoptera | Animals |
Notable species
Two of the European yellowjacket species, the German wasp (Vespula germanica), and the common wasp (Vespula vulgaris) were originally native to Europe, but are now established as invasives in southern Africa, New Zealand, eastern Australia, and South America.
The North American yellowjacket (Vespula alascensis), eastern yellowjacket (Vespula maculifrons), western yellowjacket (Vespula pensylvanica), and prairie yellowjacket (Vespula atropilosa) are native to North America.
Southern yellowjacket (Vespula squamosa), a species that is sometimes free-living and sometimes a social parasite
Bald-faced hornets (Dolichovespula maculata) belong among the yellowjackets rather than the true hornets. They are not usually called "yellowjackets" because of their ivory-on-black coloration.
Aerial yellowjacket (Dolichovespula arenaria)
Tree wasp (Dolichovespula sylvestris)
Nest
Dolichovespula species such as the aerial yellowjacket, D. arenaria, and the bald-faced hornet, tend to create exposed aerial nests. This feature is shared with some true hornets, which has led to some naming confusion.
Vespula species, in contrast, build concealed nests, usually underground.
Yellowjacket nests usually last for only one season, dying off in winter. The nest is started by a single queen, called the "foundress". Typically, a nest can reach the size of a basketball by the end of a season. In parts of Australia, New Zealand, the Pacific Islands, and southern coastal areas of the United States, the winters are mild enough to allow nest overwintering. Nests that survive multiple seasons become massive and often possess multiple egg-laying queens.
In the United States | Yellowjacket | Wikipedia | 390 | 314968 | https://en.wikipedia.org/wiki/Yellowjacket | Biology and health sciences | Hymenoptera | Animals |
The German yellowjacket (V. germanica) first appeared in Ohio in 1975, and has now become the dominant species over the eastern yellowjacket. It is bold and aggressive and can sting repeatedly and painfully. It will mark aggressors and pursue them. It is often confused with Polistes dominula, another invasive species in the United States, due to their very similar pattern. The German yellowjacket builds its nests in cavities—not necessarily underground—with the peak worker population in temperate areas between 1000 and 3000 individuals between May and August. Each colony produces several thousand new reproductives after this point through November.
The eastern yellowjacket builds its nests underground, also with the peak worker population between 1000 and 3000 individuals, similar to the German yellowjacket. Nests are built entirely of wood fiber and are completely enclosed except for a small entrance at the bottom. The color of the paper is highly dependent on the source of the wood fibers used. The nests contain multiple, horizontal tiers of combs within. Larvae hang within the combs.
In the southeastern United States, where southern yellowjacket (Vespula squamosa) nests may persist through the winter, colony sizes of this species may reach 100,000 adult wasps. The same kind of nest expansion has occurred in Hawaii with the invasive western yellowjacket (V. pensylvanica).
In popular culture
The yellowjacket's most visible place in US sporting culture is as a mascot, most famously with the Georgia Tech Yellow Jackets, represented by the mascot Buzz. Other college and university examples include Allen University, the American International College, Baldwin-Wallace University, Black Hills State University, Cedarville University, Defiance College, Graceland University, Howard Payne University, LeTourneau University, Montana State University Billings, Northern Vermont University-Lyndon, Randolph-Macon College, University of Rochester, University of Wisconsin–Superior, West Virginia State University, and Waynesburg University.
Though not specified by the team, the mascot of the Columbus Blue Jackets, named "Stinger," closely resembles a yellowjacket. In the years since its original yellow incarnation, the mascot's color has been changed to light green, seemingly combining the real insect's yellow and the team's blue.
In the United Kingdom the rugby union team Wasps RFC traditionally used a yellowjacket as their club emblem. | Yellowjacket | Wikipedia | 485 | 314968 | https://en.wikipedia.org/wiki/Yellowjacket | Biology and health sciences | Hymenoptera | Animals |
The Marvel Comics character Yellowjacket, who is based on the insect, is one of the various identities adopted by Hank Pym, who is most commonly known as Ant-Man. In addition to being able to fly, emit bio-electrictry inspired by a yellowjacket's sting, and shrink down to insect size, Yellowjacket can also control the insect and uses them to aid him in various ways.
The television series, Yellowjackets, features a girls’ soccer team which gets stranded in the wilderness and resorts to extreme measures to survive. Their mascot is a Yellowjacket, and the theme song features images of the insect as well.
Note that yellowjacket is often spelled as two words (yellow jacket) in popular culture and even in some dictionaries. The proper entomological spelling, according to the Entomological Society of America, is as a single word (yellowjacket). | Yellowjacket | Wikipedia | 188 | 314968 | https://en.wikipedia.org/wiki/Yellowjacket | Biology and health sciences | Hymenoptera | Animals |
The ricefishes are a family (Adrianichthyidae) of small ray-finned fish that are found in fresh and brackish waters from India to Japan and out into the Malay Archipelago, most notably Sulawesi (where the Lake Poso and Lore Lindu species are known as buntingi). The common name ricefish derives from the fact that some species are found in rice paddies. This family consists of about 37 species in two genera (some recognize a third, Xenopoecilus). Several species are rare and threatened, and some 2–4 may already be extinct.
Description
Most of these species are quite small, making them of interest for aquaria. Adrianichthys reach lengths of depending on the exact species involved, while the largest Oryzias reaches up to . Most Oryzias species are less than a half this length, with the smallest being up to only long. They have a number of distinctive features, including an unusual structure to the jaw, and the presence of an additional bone in the tail.
The Japanese rice fish (O. latipes), also known as the medaka, is a popular model organism used in research in developmental biology. This species has traveled into space, where they have the distinction of being the first vertebrate to mate and produce healthy young in space.
Genetic study of the family suggests that it originally evolved on Sulawesi and spread from there to the Asian mainland; the supposed genus Xenopoecilus are apparently unrelated, morphologically divergent species of Oryzias.
Taxonomy
The ricefish were formerly classified within the order Cyprinodontiformes but in the 1980s workers showed that they were a monophyletic grouping, mainly based on the characters on the bones of the gill arches and the hyoid apparatus, within the Beloniformes as the family Adrianichthyidae, this family making up one of the three suborders of the Beloniformes, the Adrianichthyoidei. Since then some workers have placed them in the Cyprinodontiformes but more recently molecular studies have supported their placement in the Beloniformes.
History
Ricefish are believed to have been kept as aquarium fishes since the 17th century. The Japanese ricefish was one of the first species to be kept and it has been bred into a golden color, from their original white coloring. | Ricefish | Wikipedia | 488 | 315245 | https://en.wikipedia.org/wiki/Ricefish | Biology and health sciences | Acanthomorpha | Animals |
Reproduction
As with most fish, ricefish typically spawn their eggs, which are fertilised externally. However, some species, including the Japanese ricefish, are known to fertilise the eggs internally, carrying them inside the body as the embryo develops. The female then lays the eggs just before they hatch. Several other species carry their eggs attached to the body between their pelvic fins. | Ricefish | Wikipedia | 81 | 315245 | https://en.wikipedia.org/wiki/Ricefish | Biology and health sciences | Acanthomorpha | Animals |
A blade is the sharp, cutting portion of a tool, weapon, or machine, specifically designed to puncture, chop, slice, or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are intended to cut. This includes early examples made from flaked stones like flint or obsidian, evolving through the ages into metal forms like copper, bronze, and iron, and culminating in modern versions made from steel or ceramics. Serving as one of humanity's oldest tools, blades continue to have wide-ranging applications, including in combat, cooking, and various other everyday and specialized tasks.
Blades function by concentrating force at the cutting edge. Design variations, such as serrated edges found on bread knives and saws, serve to enhance this force concentration, adapting blades for specific functions and materials. Blades thus hold a significant place both historically and in contemporary society, reflecting an evolution in material technology and utility.
Uses
During food preparation, knives are mainly used for slicing, chopping, and piercing.
In combat, a blade may be used to slash or puncture, and may also be thrown or otherwise propelled. The function is to sever a nerve, muscle or tendon fibers, or blood vessel to disable or kill the adversary. Severing a major blood vessel typically leads to death due to exsanguination.
Blades may be used to scrape, moving the blade sideways across a surface, as in an ink eraser, rather than along or through a surface. For construction equipment such as a grader, the ground-working implement is also referred to as the blade, typically with a replaceable cutting edge.
Physics
A simple blade intended for cutting has two faces that meet at an edge. Ideally, this edge would have no roundness but in practice, all edges can be seen to be rounded to some degree under magnification either optically or with an electron microscope. Force is applied to the blade, either from the handle or pressing on the back of the blade. The handle or back of the blade has a large area compared to the fine edge. This concentration of applied force onto the small edge area increases the pressure exerted by the edge. It is this high pressure that allows a blade to cut through a material by breaking the bonds between the molecules, crystals, fibers, etc. in the material. This necessitates the blade being strong enough to resist breaking before the other material gives way.
Geometry | Blade | Wikipedia | 494 | 315320 | https://en.wikipedia.org/wiki/Blade | Technology | Rigid components | null |
The angle at which the faces meet is important as a larger angle will make for a duller blade while making the edge stronger. A stronger edge is less likely to dull from fracture or have the edge roll out of shape.
The shape of the blade is also important. A thicker blade will be heavier and stronger and stiffer than a thinner one of similar design while also making it experience more drag while slicing or piercing. A filleting knife will be thin enough to be very flexible while a carving knife will be thicker and stiffer; a dagger will be thin so it can pierce, while a camping knife will be thicker so it can be stronger and more durable. A strongly curved edge, like a talwar, will allow the user to draw the edge of the blade against an opponent even while close to the opponent where a straight sword would be more difficult to pull in the same fashion. The curved edge of an axe means that only a small length of the edge will initially strike the tree, concentrating force as does a thinner edge, whereas a straight edge could potentially land with the full length of its edge against a flat section of the tree. A splitting maul has a convex section to avoid getting stuck in the wood where chopping axes can be flat or even concave. A khopesh, falchion, or kukri is angled and/or weighted at the distal end so that force is concentrated at the faster moving, heavier part of the blade maximizing cutting power and making it largely unsuitable for thrusting, whereas a rapier is thin and tapered allowing it to pierce and be moved with more agility while reducing its chopping power compared to a similarly sized sword. | Blade | Wikipedia | 340 | 315320 | https://en.wikipedia.org/wiki/Blade | Technology | Rigid components | null |
A serrated edge, such as on a saw or a bread knife, concentrates force onto the tips of the serrations which increases pressure as well as allowing soft or fibrous material (like wood, rope, bread, and vegetables) to expand into the spaces between serrations. Whereas pushing any knife, even a bread knife, down onto a bread loaf will just squash the loaf as bread has a low elastic modulus (is soft) but high yield strain (loosely, can be stretched or squashed by a large proportion without breaking), drawing serrations across the loaf with little downward force will allow each serration to simultaneously cut the bread with much less deformation of the loaf. Similarly, pushing on a rope tends to squash the rope while drawing serrations across it sheers the rope fibers. Drawing a smooth blade is less effective as the blade is parallel to the direction draw but the serrations of a serrated blade are at an angle to the fibers. Serrations on knives are often symmetric allowing the blade to cut on both the forward and reverse strokes of a cut, a notable exception being Veff serrations which are designed to maximize cutting power while moving the blade away from the user. Saw blade serrations, for both wood and metal, are typically asymmetrical so that they cut while moving in only one direction. (Saws act by abrading a material into dust along a narrow channel, the kerf, whereas knives and similar act by forcing the material apart. This means that saws result in a loss of material and the serrations of a saw also serve to carry metal swarf and sawdust out of the cut channel.)
Fullers are longitudinal channels either forged into the blade or later machined/milled out of the blade though the latter process is less desirable. This loss of material necessarily weakens the blade but serves to make the blade lighter without sacrificing stiffness. The same principle is applied in the manufacture of beams such as I-beams. Fullers are only of significant utility in swords. In most knives there is so little material removed by the fuller that it makes little difference to the weight of the blade and they are largely cosmetic. | Blade | Wikipedia | 446 | 315320 | https://en.wikipedia.org/wiki/Blade | Technology | Rigid components | null |
Materials
Typically blades are made from a material that is about as hard, though usually harder, than the material to be cut. Insufficiently hard blades will be unable to cut a material or will wear away quickly as hardness is related to a material's ability to resist abrasion. However, blades must also be tough enough to resist the dynamic load of impact and as a general rule the harder a blade the less tough (the more brittle) a material. For example, a steel axehead is much harder than the wood it is intended to cut and is sufficiently tough to resist the impact resulting when swung against a tree while a ceramic kitchen knife, harder than steel, is very brittle (has low toughness) and can easily shatter if dropped onto the floor or twisted while inside the food it is cutting or carelessly stored under other kitchen utensils. This creates a tension between the intended use of the blade, the material it is to be made from, and any manufacturing processes (such as heat treatment in the case of steel blades that will affect a blade's hardness and toughness). A balance must be found between the sharpness and how well it can last. Methods that can circumvent this include differential hardening. This method yields an edge that can hold its sharpness as well as a body that is tough.
Non-metals | Blade | Wikipedia | 273 | 315320 | https://en.wikipedia.org/wiki/Blade | Technology | Rigid components | null |
Prehistorically, and in less technologically advanced cultures even into modern times, tool and weapon blades have been made from wood, bone, and stone. Most woods are exceptionally poor at holding edges and bone and stone suffer from brittleness making them suffer from fracture when striking or struck. In modern times stone, in the form of obsidian, is used in some medical scalpels as it is capable of being formed into an exceedingly fine edge. Ceramic knives are non-metallic and non-magnetic. As non-metals do not corrode they remain rust and corrosion free but they suffer from similar faults as stone and bone, being rather brittle and almost entirely inflexible. They are harder than metal knives and so more difficult to sharpen, and some ceramic knives may be as hard or harder than some sharpening stones. For example, synthetic sapphire is harder than natural sharpening stones and is as hard as alumina sharpening stones. Zirconium dioxide is also harder than garnet sharpening stones and is nearly as hard as alumina. Both require diamond stones or silicon carbide stones to sharpen and care has to be taken to avoid chipping the blade. As such ceramic knives are seldom used outside of a kitchen and they are still quite uncommon. Plastic knives are difficult to make sharp and poorly retain an edge. They are largely used as low cost, disposable utensils or as children's utensils or in environments such as air travel where metal blades are prohibited. They are often serrated to compensate for their general lack of sharpness but, as evidenced by the fact they can cut food, they are still capable of inflicting injury. Plastic blades of designs other than disposable cutlery are prohibited or restricted in some jurisdictions as they are undetectable by metal detectors.
Metals
Native copper was used to make blades by ancient civilizations due to its availability. Copper's comparative softness causes it to deform easily; it does not hold an edge well and is poorly suited for working stone. Bronze is superior in this regard, and was taken up by later civilizations. Both bronze and copper can be work hardened by hitting the metal with a hammer. With technological advancement in smelting, iron came to be used in the manufacturing of blades. Steel, a range of alloys made from iron, has become the metal of choice for the modern age. | Blade | Wikipedia | 487 | 315320 | https://en.wikipedia.org/wiki/Blade | Technology | Rigid components | null |
Various alloys of steel can be made which offer a wide range of physical and chemical properties desirable for blades. For example, surgical scalpels are often made of stainless steel so that they remain free of rust and largely chemically inert; tool steels are hard and impact resistant (and often expensive as retaining toughness and hardness requires expensive alloying materials, and, being hard, they are difficult to make into their finished shape) and some are designed to resist changes to their physical properties at high temperatures. Steels can be further heat treated to optimize their toughness, which is important for impact blades, or their hardness, which allows them to retain an edge well with use (although harder metals require more effort to sharpen).
Combined materials and heat-treatments
It is possible to combine different materials, or different heat treatments, to produce desirable qualities in a blade. For example, the finest Japanese swords were routinely made of up to seven sections of metals and even poorer quality swords were often made of two. These would include soft irons that could absorb the energy of impact without fracturing but which would bend and poorly retain an edge, and hard steels more liable to shatter on impact but which retained an edge well. The combination provided a sword that would resist impact while remaining sharp, even though the edge could chip if abused. Pattern welding involved forging together twisted bars of soft (bendable) low carbon and hard (brittle) higher carbon iron. This was done because furnaces of the time were typically able to produce only one grade or the other, and neither was well suited for more than a very limited use blade. The ability of modern steelmakers to produce very high-quality steels of various compositions has largely relegated this technique to either historical recreations or to artistic works. Acid etching and polishing blades made of different grades of steel can be used to produce decorative or artistic effects.
Japanese sword makers developed the technique of differential hardening by covering their sword blades in different thicknesses of clay before quenching. Thinner clay allowed the heated metal to cool faster, particularly along the edge. Faster cooling resulted in a finer crystal structure, resulting in a blade with a hard edge but a more flexible body. European sword makers produced similar results using differential tempering.
Dulling
Blades dull with use and abuse. This is particularly true of acute blades and those made of soft materials. Dulling usually occurs due to contact between the blade and a hard substance such as ceramic, stone, bone, glass, or metal. | Blade | Wikipedia | 509 | 315320 | https://en.wikipedia.org/wiki/Blade | Technology | Rigid components | null |
The more acute the blade, the more easily it will dull. As the blade near the edge is thinner, there is little material to remove before the edge is worn away to a thicker section. Thin edges can also roll over when force is applied it them, forming a section like the bottom part of a letter "J". For this reason, straight edge razors are frequently stropped to straighten the edge.
Drawing a blade across any material tends to abrade both the blade, usually making it duller, and the cut material. Though softer than glass or many types of stone used in the kitchen, steel edges can still scratch these surfaces. The resulting scratch is full of very fine particles of ground glass or stone which will very quickly abrade the blade's edge and so dull it.
In times when swords were regularly used in warfare, they required frequent sharpening because of dulling from contact with rigid armor, mail, metal rimmed shields, or other swords, for example. Particularly, hitting the edge of another sword by accident or in an emergency could chip away metal and even cause cracks through the blade. Soft-cored blades are more resistant to fracturing on impact.
Nail pulls
Folding pocket knives often have a groove cut in the side of the blade near the spine. This is called a nail pull and allows the fingernail to be inserted to swing the blade out of the holder.
Knife patterns
Some of the most common shapes are listed below.
S1 A straight back blade, also called standard or normal, has a curving edge and a straight back. A dull back lets the wielder use fingers to concentrate force; it also makes the knife heavy and strong for its size. The curve concentrates force on a smaller area, making cutting easier. This knife can chop as well as pick and slice. This is also the best single-edged blade shape for thrusting, as the edge cuts a swath that the entire width of the knife can pass through without the spine having to push aside any material on its path, as a sheepsfoot or drop-point knife would.
S2 A trailing-point knife has a back edge that curves upward to end above the spine. This lets a lightweight knife have a larger curve on its edge and indeed the whole of the knife may be curved. Such a knife is optimized for slicing or slashing. Trailing point blades provide a larger cutting area, or belly, and are common on skinning knives. | Blade | Wikipedia | 499 | 315320 | https://en.wikipedia.org/wiki/Blade | Technology | Rigid components | null |
S3 A drop point blade has a convex curve of the back towards the point. It handles much like the clip-point, though with a stronger point typically less suitable for piercing. Swiss army pocket knives often have drop-points on their larger blades.
S4 A clip-point blade is like a normal blade with the back "clipped". This clip can be either straight or concave. The back edge of the clip may have a false edge that could be sharpened to make a second edge. The sharp tip is useful as a pick, or for cutting in tight places. If the false edge is sharpened it increases the knife's effectiveness in piercing. As well, having the tip closer to the center of the blade allows greater control in piercing. The Bowie knife has a clip point blade and clip-points are common on pocket knives and other folding knives.
S5 A blade has a straight edge and a straight dull back that curves towards the edge at the end. It gives the most control because the dull back edge is made to be held by fingers. Sheepsfoot blades were originally made to trim the hooves of sheep; their shape bears no similarity to the foot of a sheep.
S6 A Wharncliffe blade is similar in profile to a sheep's foot but the curve of the back edge starts closer to the handle and is more gradual. Its blade is much thicker than a knife of comparable size. Wharncliffes were used by sailors, as the shape of the tip prevented accidental penetration of the work or the user's hand with the sudden motion of a ship.
S7 A spey point blade (once used for neutering livestock) has a single, sharp, straight edge that curves strongly upwards at the end to meet a short, dull, straight point from the dull back. With the curved end of the blade being closer to perpendicular to the blade's axis than other knives and lacking a point, making penetration unlikely, spey blades are common on Trapper style pocketknives for skinning fur-bearing animals.
C1 Leaf blade with a distinctive recurved "waist" adding some curved "belly" to the knife facilitating slicing as well as shifting weight towards the tip meaning that it is commonly used for throwing knives as well as improving chopping ability. | Blade | Wikipedia | 466 | 315320 | https://en.wikipedia.org/wiki/Blade | Technology | Rigid components | null |
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