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The European hare has a wide range across Europe and western Asia and has been introduced to a number of other countries around the globe, often as a game species. In general it is considered moderately abundant in its native range, but declines in populations have been noted in many areas since the 1960s. These have been associated with the intensification of agricultural practices. The hare is an adaptable species and can move into new habitats, but it thrives best when there is an availability of a wide variety of weeds and other herbs to supplement its main diet of grasses. The hare is considered a pest in some areas; it is more likely to damage crops and young trees in winter when there are not enough alternative foodstuffs available.
The International Union for Conservation of Nature has evaluated the European hare's conservation status as being of least concern. However, at low population densities, hares are vulnerable to local extinctions as the available gene pool declines, making inbreeding more likely. This is the case in northern Spain and in Greece, where the restocking by hares brought from outside the region has been identified as a threat to regional gene pools. To counteract this, a captive breeding program has been implemented in Spain, and the relocation of some individuals from one location to another has increased genetic variety. The Bern Convention lists the hare under Appendix III as a protected species. Several countries, including Norway, Germany, Austria and Switzerland, have placed the species on their Red Lists as "near threatened" or "threatened". | European hare | Wikipedia | 307 | 322239 | https://en.wikipedia.org/wiki/European%20hare | Biology and health sciences | Lagomorphs | Animals |
Ecological succession is the process of change in the species that make up an ecological community over time.
The process of succession occurs either after the initial colonization of a newly created habitat, or after a disturbance substantially alters a pre-existing habitat. Succession that begins in new habitats, uninfluenced by pre-existing communities, is called primary succession, whereas succession that follows disruption of a pre-existing community is called secondary succession. Primary succession may happen after a lava flow or the emergence of a new island from the ocean. Surtsey, a volcanic island off the southern coast of Iceland, is an important example of a place where primary succession has been observed. On the other hand, secondary succession happens after disturbance of a community, such as from a fire, severe windthrow, or logging.
Succession was among the first theories advanced in ecology. Ecological succession was first documented in the Indiana Dunes of Northwest Indiana and remains an important ecological topic of study. Over time, the understanding of succession has changed from a linear progression to a stable climax state, to a more complex, cyclical model that de-emphasizes the idea of organisms having fixed roles or relationships.
History
Precursors of the idea of ecological succession go back to the beginning of the 19th century. As early as 1742 French naturalist Buffon noted that poplars precede oaks and beeches in the natural evolution of a forest. Buffon was later forced by the theological committee at the University of Paris to recant many of his ideas because they contradicted the biblical narrative of Creation.
Swiss geologist Jean-André Deluc and the later French naturalist Adolphe Dureau de la Malle were the first to make use of the word succession concerning the vegetation development after forest clear-cutting. In 1859 Henry David Thoreau wrote an address called "The Succession of Forest Trees" in which he described succession in an oak-pine forest. "It has long been known to observers that squirrels bury nuts in the ground, but I am not aware that any one has thus accounted for the regular succession of forests." The Austrian botanist Anton Kerner published a study about the succession of plants in the Danube river basin in 1863. | Ecological succession | Wikipedia | 438 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Ragnar Hult's 1885 study on the stages of forest development in Blekinge noted that grassland becomes heath before the heath develops into forest. Birch dominated the early stages of forest development, then pine (on dry soil) and spruce (on wet soil). If the birch is replaced by oak it eventually develops to beechwood. Swamps proceed from moss to sedges to moor vegetation followed by birch and finally spruce.
H. C. Cowles
Between 1899 and 1910, Henry Chandler Cowles, at the University of Chicago, developed a more formal concept of succession. Inspired by studies of Danish dunes by Eugen Warming, Cowles studied vegetation development on sand dunes on the shores of Lake Michigan (the Indiana Dunes). He recognized that vegetation on dunes of different ages might be interpreted as different stages of a general trend of vegetation development on dunes (an approach to the study of vegetation change later termed space-for-time substitution, or chronosequence studies). He first published this work as a paper in the Botanical Gazette in 1899 ("The ecological relations of the vegetation of the sand dunes of Lake Michigan"). In this classic publication and subsequent papers, he formulated the idea of primary succession and the notion of a sere—a repeatable sequence of community changes specific to particular environmental circumstances.
Gleason and Clements
From about 1900 to 1960, however, understanding of succession was dominated by the theories of Frederic Clements, a contemporary of Cowles, who held that seres were highly predictable and deterministic and converged on a climatically determined stable climax community regardless of starting conditions. Clements explicitly analogized the successional development of ecological communities with ontogenetic development of individual organisms, and his model is often referred to as the pseudo-organismic theory of community ecology. Clements and his followers developed a complex taxonomy of communities and successional pathways.
Henry Gleason offered a contrasting framework as early as the 1920s. The Gleasonian model was more complex and much less deterministic than the Clementsian. It differs most fundamentally from the Clementsian view in suggesting a much greater role of chance factors and in denying the existence of coherent, sharply bounded community types. Gleason argued that species distributions responded individualistically to environmental factors, and communities were best regarded as artifacts of the juxtaposition of species distributions. Gleason's ideas, first published in 1926, were largely ignored until the late 1950s. | Ecological succession | Wikipedia | 495 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Two quotes illustrate the contrasting views of Clements and Gleason. Clements wrote in 1916:
while Gleason, in his 1926 paper, said:
Gleason's ideas were, in fact, more consistent with Cowles' original thinking about succession. About Clements' distinction between primary succession and secondary succession, Cowles wrote (1911):
Eugene Odum
In 1969, Eugene Odum published The Strategy of Ecosystem Development, a paper that was highly influential to conservation and environmental restoration. Odum argued that ecological succession was an orderly progression toward a climax state where “maximum biomass and symbiotic function between organisms are maintained per unit energy flow." Odum highlighted how succession was not merely a change in the species composition of an ecosystem, but also created change in more complex attributes of the ecosystem, such as structure and nutrient cycling.
Modern era
A more rigorous, data-driven testing of successional models and community theory generally began with the work of Robert Whittaker and John Curtis in the 1950s and 1960s. Succession theory has since become less monolithic and more complex. J. Connell and R. Slatyer attempted a codification of successional processes by mechanism. Among British and North American ecologists, the notion of a stable climax vegetation has been largely abandoned, and successional processes have come to be seen as much less deterministic, with important roles for historical contingency and for alternate pathways in the actual development of communities. Debates continue as to the general predictability of successional dynamics and the relative importance of equilibrial vs. non-equilibrial processes. Former Harvard professor Fakhri A. Bazzaz introduced the notion of scale into the discussion, as he considered that at local or small area scale the processes are stochastic and patchy, but taking bigger regional areas into consideration, certain tendencies can not be denied.
More recent definitions of succession highlight change as the central characteristic. New research techniques are greatly enhancing contemporary scientists' ability to study succession, which is now seen as neither entirely random nor entirely predictable.
Factors
Both consistent patterns and variability are observed in ecological succession. Theories of ecological succession identify different factors that help explain why plant communities change the way they do. | Ecological succession | Wikipedia | 452 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Diversity of possible trajectories
Ecological succession was formerly seen as an orderly progression through distinct stages, where several plant communities would replace each other in a fixed order and eventually reach a stable end point known as the climax. The climax community was sometimes referred to as the 'potential vegetation' of a site, and thought to be primarily determined by the local climate. This idea has been largely abandoned by modern ecologists in favor of nonequilibrium ideas of ecosystems dynamics. Most natural ecosystems experience disturbance at a rate that makes a "climax" community unattainable. Climate change often occurs at a rate and frequency sufficient to prevent arrival at a climax state.
The trajectory of successional change can be influenced by initial site conditions, by the type of disturbance that triggers succession, by the interactions of the species present, and by more random factors such as availability of colonists or seeds or weather conditions at the time of disturbance. Some aspects of succession are broadly predictable; others may proceed more unpredictably than in the classical view of ecological succession. Coupled with the stochastic nature of disturbance events and other long-term (e.g., climatic) changes, such dynamics make it doubtful whether the 'climax' concept ever applies or is particularly useful in considering actual vegetation.
Stochastic events
Succession is influenced partially by random chance, but it is debated how much random chance directs the trajectory of succession, as opposed to more deterministic factors. The timing of a disturbance such as a weather event may be random and unpredictable. Dispersal of propagules to a new site may also be random. However, community assembly is also determined by processes that select species non-randomly from the local species pool.
Dispersal limitation vs. environmental filtering
Succession is impacted both by the ability of seeds to disperse to new sites, and the suitability of site conditions for those seeds to grow and survive. Dispersal limitation means that even though favorable sites for a plant to live might exist, the plant's seeds may be unable to reach those sites. Environmental filtering, also called establishment limitation, implies that although seeds may be distributed to a site, those seeds may be unable to survive due to various characteristics of the site. The predicted impact of these two factors varies under different models of ecological succession. | Ecological succession | Wikipedia | 456 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Feedback loops
Ecological succession is driven by feedbacks between plants and their environment. As plants grow following a disturbance, they change their environment, for example by creating shade, attracting seed dispersers, contributing organic matter to the soil, changing the availability of soil nutrients, creating microhabitats, and buffering temperature and moisture fluctuations. This creates opportunities for different plants to grow, which causes directional change in the ecosystem. The development of some ecosystem attributes, such as soil properties and nutrient cycles, are both influenced by community properties, and, in turn, influence further successional development. This feed-back process may occur over centuries or millennia. Plants may facilitate the establishment of other plants by creating suitable conditions for them to grow, for example by providing shade or allowing for soil formation. Plants may also competitively exclude or otherwise prevent the growth of other plants.
Patterns
Though the idea of a fixed, predictable process of succession with a single well-defined climax is an overly simplified model, several predictions made by the classical model are accurate. Species diversity, overall plant biomass, plant lifespans, the importance of decomposer organisms, and overall stability all increase as a community approaches a climax state, while the rate at which soil nutrients are consumed, rate of biogeochemical cycling, and rate of net primary productivity all decrease as a community approaches a climax state.
Communities in early succession will be dominated by fast-growing, well-dispersed species (opportunist, fugitive, or r-selected life-histories). These are also called pioneer species. As succession proceeds, these species will tend to be replaced by more competitive (k-selected) species.
Some of these trends do not apply in all cases. For example, species diversity almost necessarily increases during early succession as new species arrive, but may decline in later succession as competition eliminates opportunistic species and leads to dominance by locally superior competitors. Net Primary Productivity, biomass, and trophic properties all show variable patterns over succession, depending on the particular system and site.
Disruptions
Two important perturbation factors today are human actions and climatic change. Additions to available species pools through range expansions and introductions can also continually reshape communities.
Types
Primary succession | Ecological succession | Wikipedia | 450 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Successional dynamics beginning with colonization of an area that has not been previously occupied by an ecological community are referred to as primary succession. This includes newly exposed rock or sand surfaces, lava flows, and newly exposed glacial tills. The stages of primary succession include pioneer microorganisms, plants (lichens and mosses), grassy stage, smaller shrubs, and trees. Animals begin to return when there is food there for them to eat. When it is a fully functioning ecosystem, it has reached the climax community stage.
Secondary succession
Secondary succession follows severe disturbance or removal of a preexisting community that has remnants of the previous ecosystem. Secondary succession is strongly influenced by pre-disturbance conditions such as soil development, seed banks, remaining organic matter, and residual living organisms. Because of residual fertility and preexisting organisms, community change in early stages of secondary succession can be relatively rapid.
Secondary succession is much more commonly observed and studied than primary succession. Particularly common types of secondary succession include responses to natural disturbances such as fire, flood, and severe winds, and to human-caused disturbances such as logging and agriculture. In secondary succession, the soils and organisms need to be left unharmed so there is a way for the new material to rebuild.
As an example, in a fragmented old field habitat created in eastern Kansas, woody plants "colonized more rapidly (per unit area) on large and nearby patches".
Secondary succession can quickly change a landscape. In the 1900s, Acadia National Park had a wildfire that destroyed much of the landscape. Originally evergreen trees grew in the landscape. After the fire, the area took at least a year to grow shrubs. Eventually, deciduous trees started to grow instead of evergreens.
Secondary succession has been occurring in Shenandoah National Park following the 1995 flood of the Moorman's and Rapidan rivers, which destroyed plant and animal life.
Seasonal and cyclic dynamics
Unlike secondary succession, these types of vegetation change are not dependent on disturbance but are periodic changes arising from fluctuating species interactions or recurring events. These models modify the climax concept towards one of dynamic states.
Causes of plant succession | Ecological succession | Wikipedia | 430 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Autogenic succession can be brought by changes in the soil caused by the organisms there. These changes include accumulation of organic matter in litter or humic layer, alteration of soil nutrients, or change in the pH of soil due to the plants growing there. The structure of the plants themselves can also alter the community. For example, when larger species like trees mature, they produce shade on to the developing forest floor that tends to exclude light-requiring species. Shade-tolerant species will invade the area.
Allogenic succession is caused by external environmental influences and not by the vegetation. For example, soil changes due to erosion, leaching or the deposition of silt and clays can alter the nutrient content and water relationships in the ecosystems. Animals also play an important role in allogenic changes as they are pollinators, seed dispersers and herbivores. They can also increase nutrient content of the soil in certain areas, or shift soil about (as termites, ants, and moles do) creating patches in the habitat. This may create regeneration sites that favor certain species.
Climatic factors may be very important, but on a much longer time-scale than any other. Changes in temperature and rainfall patterns will promote changes in communities. As the climate warmed at the end of each ice age, great successional changes took place. The tundra vegetation and bare glacial till deposits underwent succession to mixed deciduous forest. The greenhouse effect resulting in increase in temperature is likely to bring profound Allogenic changes in the next century. Geological and climatic catastrophes such as volcanic eruptions, earthquakes, avalanches, meteors, floods, fires, and high wind also bring allogenic changes.
Mechanisms
In 1916, Frederic Clements published a descriptive theory of succession and advanced it as a general ecological concept. His theory of succession had a powerful influence on ecological thought. Clements' concept is usually termed classical ecological theory.
According to Clements, succession is a process involving several phases:
Nudation: Succession begins with the development of a bare site, called Nudation (disturbance).
Migration: refers to arrival of propagules.
Ecesis: involves establishment and initial growth of vegetation.
Competition: as vegetation becomes well established, grows, and spreads, various species begin to compete for space, light and nutrients.
Reaction: during this phase autogenic changes such as the buildup of humus affect the habitat, and one plant community replaces another.
Stabilization: a supposedly stable climax community forms.
Seral communities | Ecological succession | Wikipedia | 494 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
A seral community is an intermediate stage found in an ecosystem advancing towards its climax community. In many cases more than one seral stage evolves until climax conditions are attained. A prisere is a collection of seres making up the development of an area from non-vegetated surfaces to a climax community. Depending on the substratum and climate, different seres are found.
Changes in animal life
Succession theory was developed primarily by botanists. The study of succession applied to whole ecosystems initiated in the writings of Ramon Margalef, while Eugene Odum's publication of The Strategy of Ecosystem Development is considered its formal starting point.
Animal life also exhibits changes with changing communities. In the lichen stage, fauna is sparse. It comprises a few mites, ants, and spiders living in cracks and crevices. The fauna undergoes a qualitative increase during the herb grass stage. The animals found during this stage include nematodes, insect larvae, ants, spiders, mites, etc. The animal population increases and diversifies with the development of the forest climax community. The fauna consists of invertebrates like slugs, snails, worms, millipedes, centipedes, ants, bugs; and vertebrates such as squirrels, foxes, mice, moles, snakes, various birds, salamanders and frogs.
A review of succession research by Hodkinson et al. (2002) documented what was likely first noted by Darwin during his voyage on the H.M.S. Beagle:
These naturalists note that prior to the establishment of autotrophs, there is a foodweb formed by heterotrophs built on allochthonous inputs of dead organic matter (necromass). Work on volcanic systems such as Kasatochi Volcano in the Aleutians by Sikes and Slowik (2010) supports this idea.
Microsuccession | Ecological succession | Wikipedia | 389 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Succession of micro-organisms including fungi and bacteria occurring within a microhabitat is known as microsuccession or serule. In artificial bacterial meta-communities of motile strains on-chip it has been shown that ecological succession is based on a trade-off between colonization and competition abilities. To exploit locations or explore the landscape? Escherichia coli is a fugitive species, whereas Pseudomonas aeruginosa is a slower colonizer but superior competitor. Like in plants, microbial succession can occur in newly available habitats (primary succession) such as surfaces of plant leaves, recently exposed rock surfaces (i.e., glacial till) or animal infant guts, and also on disturbed communities (secondary succession) like those growing in recently dead trees, decaying fruits, or animal droppings. Microbial communities may also change due to products secreted by the bacteria present. Changes of pH in a habitat could provide ideal conditions for a new species to inhabit the area. In some cases the new species may outcompete the present ones for nutrients leading to the primary species demise. Changes can also occur by microbial succession with variations in water availability and temperature. Theories of macroecology have only recently been applied to microbiology and so much remains to be understood about this growing field. A recent study of microbial succession evaluated the balances between stochastic and deterministic processes in the bacterial colonization of a salt marsh chronosequence. The results of this study show that, much like in macro succession, early colonization (primary succession) is mostly influenced by stochasticity while secondary succession of these bacterial communities was more strongly influenced by deterministic factors.
Climax concept
According to classical ecological theory, succession stops when the sere has arrived at an equilibrium or steady state with the physical and biotic environment. Barring major disturbances, it will persist indefinitely. This end point of succession is called climax.
Climax community
The final or stable community in a sere is the climax community or climatic vegetation. It is self-perpetuating and in equilibrium with the physical habitat. There is no net annual accumulation of organic matter in a climax community. The annual production and use of energy is balanced in such a community.
Characteristics | Ecological succession | Wikipedia | 454 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
The vegetation is tolerant of environmental conditions.
It has a wide diversity of species, a well-drained spatial structure, and complex food chains.
The climax ecosystem is balanced. There is equilibrium between gross primary production and total respiration, between energy used from sunlight and energy released by decomposition, between uptake of nutrients from the soil and the return of nutrient by litter fall to the soil.
Individuals in the climax stage are replaced by others of the same kind. Thus the species composition maintains equilibrium.
It is an index of the climate of the area. The life or growth forms indicate the climatic type.
Types of climax | Ecological succession | Wikipedia | 122 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Climatic Climax If there is only a single climax and the development of climax community is controlled by the climate of the region, it is termed as climatic climax. For example, development of Maple-beech climax community over moist soil. Climatic climax is theoretical and develops where physical conditions of the substrate are not so extreme as to modify the effects of the prevailing regional climate.
Edaphic Climax When there are more than one climax communities in the region, modified by local conditions of the substrate such as soil moisture, soil nutrients, topography, slope exposure, fire, and animal activity, it is called edaphic climax. Succession ends in an edaphic climax where topography, soil, water, fire, or other disturbances are such that a climatic climax cannot develop.
Catastrophic Climax Climax vegetation vulnerable to a catastrophic event such as a wildfire. For example, in California, chaparral vegetation is the final vegetation. The wildfire removes the mature vegetation and decomposers. A rapid development of herbaceous vegetation follows until the shrub dominance is re-established. This is known as catastrophic climax.
Disclimax When a stable community, which is not the climatic or edaphic climax for the given site, is maintained by man or his domestic animals, it is designated as Disclimax (disturbance climax) or anthropogenic subclimax (man-generated). For example, overgrazing by stock may produce a desert community of bushes and cacti where the local climate actually would allow grassland to maintain itself.
Subclimax The prolonged stage in succession just preceding the climatic climax is subclimax.
Preclimax and Postclimax In certain areas different climax communities develop under similar climatic conditions. If the community has life forms lower than those in the expected climatic climax, it is called preclimax; a community that has life forms higher than those in the expected climatic climax is postclimax. Preclimax strips develop in less moist and hotter areas, whereas Postclimax strands develop in more moist and cooler areas than that of surrounding climate.
Theories
There are three schools of interpretations explaining the climax concept: | Ecological succession | Wikipedia | 435 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Monoclimax or Climatic Climax Theory was advanced by Clements (1916) and recognizes only one climax whose characteristics are determined solely by climate (climatic climax). The processes of succession and modification of environment overcome the effects of differences in topography, parent material of the soil, and other factors. The whole area would be covered with uniform plant community. Communities other than the climax are related to it, and are recognized as subclimax, postclimax and disclimax.
Polyclimax Theory was advanced by Tansley (1935). It proposes that the climax vegetation of a region consists of more than one vegetation climaxes controlled by soil moisture, soil nutrients, topography, slope exposure, fire, and animal activity.
Climax Pattern Theory was proposed by Whittaker (1953). The climax pattern theory recognizes a variety of climaxes governed by responses of species populations to biotic and abiotic conditions. According to this theory the total environment of the ecosystem determines the composition, species structure, and balance of a climax community. The environment includes the species' responses to moisture, temperature, and nutrients, their biotic relationships, availability of flora and fauna to colonize the area, chance dispersal of seeds and animals, soils, climate, and disturbance such as fire and wind. The nature of climax vegetation will change as the environment changes. The climax community represents a pattern of populations that corresponds to and changes with the pattern of environment. The central and most widespread community is the climatic climax.
The theory of alternative stable states suggests there is not one end point but many which transition between each other over ecological time.
Succession by habitat type
Forest succession | Ecological succession | Wikipedia | 332 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Forests, being an ecological system, are subject to the species succession process. There are "opportunistic" or "pioneer" species that produce great quantities of seed that are disseminated by the wind, and therefore can colonize big empty extensions. They are capable of germinating and growing in direct sunlight. Once they have produced a closed canopy, the lack of direct sun radiation at the soil makes it difficult for their own seedlings to develop. It is then the opportunity for shade-tolerant species to become established under the protection of the pioneers. When the pioneers die, the shade-tolerant species replace them. These species are capable of growing beneath the canopy, and therefore, in the absence of disturbances, will stay. For this reason it is then said the stand has reached its climax. When a disturbance occurs, the opportunity for the pioneers opens up again, provided they are present or within a reasonable range.
An example of pioneer species, in forests of northeastern North America are Betula papyrifera (White birch) and Prunus serotina (Black cherry), that are particularly well-adapted to exploit large gaps in forest canopies, but are intolerant of shade and are eventually replaced by other shade-tolerant species in the absence of disturbances that create such gaps. In the tropics, well known pioneer forest species can be found among the genera Cecropia, Ochroma and Trema.
Things in nature are not black and white, and there are intermediate stages. It is therefore normal that between the two extremes of light and shade there is a gradient, and there are species that may act as pioneer or tolerant, depending on the circumstances. It is of paramount importance to know the tolerance of species in order to practice an effective silviculture.
Wetland succession
Since many types of wetland environments exist, succession may follow a wide array of trajectories and patterns in wetlands. Under the classical model, the process of secondary succession holds that a wetland progresses over time from an initial state of open water with few plants, to a forested climax state where decayed organic matter has built up over time, forming peat. However, many wetlands are maintained by regular disturbance or natural processes at an equilibrium state that does not resemble the predicted forested "climax." The idea that ponds and wetlands gradually fill in to become dry land has been criticized and called into question due to lack of evidence. | Ecological succession | Wikipedia | 492 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Wetland succession is a uniquely complex, non-linear process shaped by hydrology. Hydrological factors often work against linear processes that predict a succession to a "climax" state. The energy carried by moving water may create a continuous source of disturbance. For example, in coastal wetlands, the tides moving in and out continuously acts upon the ecological community. Fire may also maintain an equilibrium state in a wetland by burning off vegetation, thus interrupting the accumulation of peat.
Water entering and leaving the wetland follows patterns that are broadly cyclical but erratic. For example, seasonal flooding and drying may occur with yearly changes in precipitation, causing seasonal changes in the wetland community that maintain it at a stable state. However, unusually heavy rain or unusually severe drought may cause the wetland to enter a positive feedback loop where it begins to change in a linear direction. Since wetlands are sensitive to changes in the natural processes that maintain them, human activities, invasive species, and climate change could initiate long-term changes in wetland ecosystems.
Grassland succession
For a long time, grasslands were thought to be early stages of succession, dominated by weedy species and with little conservation value. However, comparing grasslands that form after recovery from long-term disruptions like agricultural tillage with ancient or "old-growth" grasslands has shown that grasslands are not inherently early-successional communities. Rather, grasslands undergo a centuries-long process of succession, and a grassland that is tilled up for agriculture or otherwise destroyed is estimated to take a minimum of 100 years, and potentially on average 1,400 years, to recover to its previous level of biodiversity. However, planting a high diversity of late-successional grassland species in a disturbed environment can accelerate the recovery of the soil's ability to sequester carbon, resulting in twice as much carbon storage as a naturally recovering grassland over the same period of time. | Ecological succession | Wikipedia | 372 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
Many grassland ecosystems are maintained by disturbance, such as fire and grazing by large animals, or else the process of succession will change them to forest or shrubland. In fact, it is debated whether fire should be considered disturbance at all for the North American prairie ecosystems, since it maintains, rather than disrupts, an equilibrium state. Many late-successional grassland species have adaptations that allow them to store nutrients underground and re-sprout rapidly after "aboveground" disturbances like fire or grazing. Disturbance events that severely disrupt or destroy the soil, such as tilling, eliminate these late-successional species, reverting the grassland to an early successional stage dominated by pioneers, whereas fire and grazing benefit late-successional species. Both too much and too little disturbance can damage the biodiversity of disturbance-dependent ecosystems like grasslands.
In North American semi-arid grasslands, the introduction of livestock ranching and absence of fire was observed to cause a transition away from grasses to woody vegetation, particularly mesquite. However, the means by which ecological succession under frequent disturbance results in ecosystems of the sort seen in remnant prairies is poorly understood. | Ecological succession | Wikipedia | 231 | 322376 | https://en.wikipedia.org/wiki/Ecological%20succession | Biology and health sciences | Ecology | Biology |
An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also be a nidus (starting point) for clot formation (thrombosis) and embolization. As an aneurysm increases in size, the risk of rupture, which leads to uncontrolled bleeding, increases. Although they may occur in any blood vessel, particularly lethal examples include aneurysms of the circle of Willis in the brain, aortic aneurysms affecting the thoracic aorta, and abdominal aortic aneurysms. Aneurysms can arise in the heart itself following a heart attack, including both ventricular and atrial septal aneurysms. There are congenital atrial septal aneurysms, a rare heart defect.
Etymology
The word is from Greek: ἀνεύρυσμα, aneurysma, "dilation", from ἀνευρύνειν, aneurynein, "to dilate".
Classification
Aneurysms are classified by type, morphology, or location.
True and false aneurysms
A true aneurysm is one that involves all three layers of the wall of an artery (intima, media and adventitia). True aneurysms include atherosclerotic, syphilitic, and congenital aneurysms, as well as ventricular aneurysms that follow transmural myocardial infarctions (aneurysms that involve all layers of the attenuated wall of the heart are also considered true aneurysms).
A false aneurysm, or pseudoaneurysm, is a collection of blood leaking completely out of an artery or vein but confined next to the vessel by the surrounding tissue. This blood-filled cavity will eventually either thrombose (clot) enough to seal the leak or rupture out of the surrounding tissue.
Pseudoaneurysms can be caused by trauma that punctures the artery, such as knife and bullet wounds, as a result of percutaneous surgical procedures such as coronary angiography or arterial grafting, or use of an artery for injection.
Morphology | Aneurysm | Wikipedia | 499 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Aneurysms can also be classified by their macroscopic shapes and sizes and are described as either saccular or fusiform. The shape of an aneurysm is not specific for a specific disease. The size of the base or neck is useful in determining the chance of for example endovascular coiling.
Saccular aneurysms, or "berry" aneurysms, are spherical in shape and involve only a portion of the vessel wall; they usually range from in diameter, and are often filled, either partially or fully, by a thrombus.Saccular aneurysms have a "neck" that connects the aneurysm to its main ("parent") artery, a larger, rounded area, called the dome.
Fusiform aneurysms ("spindle-shaped" aneurysms) are variable in both their diameter and length; their diameters can extend up to . They often involve large portions of the ascending and transverse aortic arch, the abdominal aorta, or, less frequently, the iliac arteries.
Location
Aneurysms can also be classified by their location:
Arterial and venous, with arterial being more common.
The heart, including coronary artery aneurysms, ventricular aneurysms, aneurysm of sinus of Valsalva, and aneurysms following cardiac surgery.
The aorta, namely aortic aneurysms including thoracic aortic aneurysms and abdominal aortic aneurysms.
The brain, including cerebral aneurysms, berry aneurysms, and Charcot–Bouchard aneurysms.
The legs, including the popliteal arteries.
The kidney, including renal artery aneurysms and intraparenchymal aneurysms.
Capillary aneurysms are flesh-colored solitary lesions, resembling an intradermal nevus, which may suddenly grow larger and darker and become blue-black or black as a result of thrombosis.
The large vessels such as external and internal jugular veins
Cerebral aneurysms, also known as intracranial or brain aneurysms, occur most commonly in the anterior cerebral artery, which is part of the circle of Willis. This can cause severe strokes leading to death. The next most common sites of cerebral aneurysm occurrence are in the internal carotid artery.
Size | Aneurysm | Wikipedia | 504 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Abdominal aortic aneurysms are commonly divided according to their size and symptomatology. An aneurysm is usually defined as an outer aortic diameter over 3 cm (normal diameter of the aorta is around 2 cm), or more than 50% of normal diameter that of a healthy individual of the same sex and age. If the outer diameter exceeds 5.5 cm, the aneurysm is considered to be large.
The common iliac artery is classified as:
Signs and symptoms
Aneurysm presentation may range from life-threatening complications of hypovolemic shock to being found incidentally on X-ray. Symptoms will differ by the site of the aneurysm and can include:
Cerebral aneurysm
Symptoms can occur when the aneurysm pushes on a structure in the brain. Symptoms will depend on whether an aneurysm has ruptured or not. There may be no symptoms present at all until the aneurysm ruptures. For an aneurysm that has not ruptured the following symptoms can occur:
Fatigue
Loss of perception
Loss of balance
Speech problems
Double vision
For a ruptured aneurysm, symptoms of a subarachnoid hemorrhage may present:
Severe headaches
Loss of vision
Double vision
Neck pain or stiffness
Pain above or behind the eyes
Abdominal aneurysm
Abdominal aortic aneurysm involves a regional dilation of the aorta and is diagnosed using ultrasonography, computed tomography, or magnetic resonance imaging. A segment of the aorta that is found to be greater than 50% larger than that of a healthy individual of the same sex and age is considered aneurysmal. Abdominal aneurysms are usually asymptomatic but in rare cases can cause lower back pain or lower limb ischemia.
Renal (kidney) aneurysm
Flank pain and tenderness
Hypertension
Haematuria
Signs of hypovolemic shock | Aneurysm | Wikipedia | 408 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Risk factors
Risk factors for an aneurysm include diabetes, obesity, hypertension, tobacco use, alcoholism, high cholesterol, copper deficiency, increasing age, and tertiary syphilis infection. Connective tissue disorders such as Loeys-Dietz syndrome, Marfan syndrome, and certain forms of Ehlers-Danlos syndrome are also associated with aneurysms. Aneurysms, dissections, and ruptures in individuals under 40 years of age are a major diagnostic criteria of the vascular form of Ehlers-Danlos syndrome (vEDS).
Specific infective causes associated with aneurysm include:
Advanced syphilis infection resulting in syphilitic aortitis and an aortic aneurysm
Tuberculosis, causing Rasmussen's aneurysms
Brain infections, causing infectious intracranial aneurysms
A minority of aneurysms are associated with genetic factors. Examples include:
Berry aneurysms of the anterior communicating artery of the circle of Willis, associated with autosomal dominant polycystic kidney disease
Familial thoracic aortic aneurysms
Cirsoid aneurysms, secondary to congenital arteriovenous malformations
Pathophysiology
Aneurysms form for a variety of interacting reasons. Multiple factors, including factors affecting a blood vessel wall and the blood through the vessel, contribute.
The pressure of blood within the expanding aneurysm may also injure the blood vessels supplying the artery itself, further weakening the vessel wall. Without treatment, these aneurysms will ultimately progress and rupture.
Infection. A mycotic aneurysm is an aneurysm that results from an infectious process that involves the arterial wall. A person with a mycotic aneurysm has a bacterial infection in the wall of an artery, resulting in the formation of an aneurysm. One of the causes of mycotic aneurysms is infective endocarditis. The most common locations include arteries in the abdomen, thigh, neck, and arm. A mycotic aneurysm can result in sepsis, or life-threatening bleeding if the aneurysm ruptures. Less than 3% of abdominal aortic aneurysms are mycotic aneurysms. | Aneurysm | Wikipedia | 484 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Syphilis. The third stage of syphilis also manifests as aneurysm of the aorta, which is due to loss of the vasa vasorum in the tunica adventitia.
Copper deficiency. A minority of aneurysms are caused by copper deficiency, which results in a decreased activity of the lysyl oxidase enzyme, affecting elastin, a key component in vessel walls. Copper deficiency results in vessel wall thinning, and thus has been noted as a cause of death in copper-deficient humans, chickens, and turkeys.
Mechanics
Aneurysmal blood vessels are prone to rupture under normal blood pressure and flow due to the special mechanical properties that make them weaker. To better understand this phenomenon, we can first look at healthy arterial vessels which exhibit (for a biomaterial in vivo). Unlike crystalline materials whose linear elastic region follows Hooke's Law under uniaxial loading, many biomaterials exhibit a J-shaped stress-strain curve which is non-linear and concave up. The blood vessel can be under large strain, or the amount of stretch the blood vessel can undergo, for a range of low applied stress before fracture, as shown by the lower part of the curve. The area under the curve up to a given strain is much lower than that for the equivalent Hookean curve, which is correlated to toughness. Toughness is defined as the amount of energy per unit volume material can absorb before rupturing. Because the amount of energy released is proportional to the amount of crack propagation, the blood vessel wall can withstand pressure and is "tough". Thus, healthy blood vessels with the mechanical properties of the J-shaped stress-strain curve have greater stability against aneurysms than materials with linear elasticity. | Aneurysm | Wikipedia | 369 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Blood vessels with aneurysms, on the other hand, are under the influence of an S-shaped stress-strain curve. As a visual aid, aneurysms can be understood as a long, cylindrical balloon. Because it's a tight balloon under pressure, it can pop at any time stress beyond a certain force threshold is applied. In the same vein, an unhealthy blood vessel has elastic instabilities that lead to rupture. Initially, for a given radius and pressure, stiffness of the material increases linearly. At a certain point, the stiffness of the arterial wall starts to decrease with increasing load. At higher strain values, the area under the curve increases, thus increasing the impact on the material that would promote crack propagation. The differences in the mechanical properties of the aneurysmal blood vessels and the healthy blood vessels stem from the compositional differences of the vessels. Compared to normal aortas, aneurysmal aortas have a much higher volume fraction of collagen and ground substance (54.8% vs. 95.6%) and a much lower volume fraction of elastin (22.7% vs. 2.4%) and smooth muscles (22.6% vs. 2.2%), which contribute to higher initial stiffness. It was also found that the ultimate tensile strength, or the strength to withstand rupture, of aneurysmal vessel wall is 50% lower than that of normal aortas. The wall strength of ruptured aneurysmal aortic wall was also found to be 54.2 N/cm2, which is much lower than that of a repaired aorta wall, 82.3 N/cm2. Due to the change in composition of the arterial wall, aneurysms overall have much lower strength to resist rupture. Predicting the risk of rupture is difficult due to the regional anisotropy the hardened blood vessels exhibit, meaning that the stress and strength values vary depending on the region and the direction of the vessel they are measured along.
Diagnosis | Aneurysm | Wikipedia | 432 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Diagnosis of a ruptured cerebral aneurysm is commonly made by finding signs of subarachnoid hemorrhage on a computed tomography (CT) scan. If the CT scan is negative but a ruptured aneurysm is still suspected based on clinical findings, a lumbar puncture can be performed to detect blood in the cerebrospinal fluid. Computed tomography angiography (CTA) is an alternative to traditional angiography and can be performed without the need for arterial catheterization. This test combines a regular CT scan with a contrast dye injected into a vein. Once the dye is injected into a vein, it travels to the cerebral arteries, and images are created using a CT scan. These images show exactly how blood flows into the brain arteries.
Treatment
Historically, the treatment of arterial aneurysms has been limited to either surgical intervention or watchful waiting in combination with control of blood pressure. At least, in the case of abdominal aortic aneurysm (AAA), the decision does not come without significant risk and cost, hence, there is a great interest in identifying more advanced decision-making approaches that are not solely based on the AAA diameter, but involve other geometrical and mechanical nuances such as local thickness and wall stress. In recent years, endovascular or minimally invasive techniques have been developed for many types of aneurysms. Aneurysm clips are used for surgical procedure i.e. clipping of aneurysms.
Intracranial
There are currently two treatment options for brain aneurysms: surgical clipping or endovascular coiling. There is currently debate in the medical literature about which treatment is most appropriate given particular situations.
Surgical clipping was introduced by Walter Dandy of the Johns Hopkins Hospital in 1937. It consists of a craniotomy to expose the aneurysm and closing the base or neck of the aneurysm with a clip. The surgical technique has been modified and improved over the years. | Aneurysm | Wikipedia | 418 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Endovascular coiling was introduced by Italian neurosurgeon Guido Guglielmi at UCLA in 1989. It consists of passing a catheter into the femoral artery in the groin, through the aorta, into the brain arteries, and finally into the aneurysm itself. Platinum coils initiate a clotting reaction within the aneurysm that, if successful, fills the aneurysm dome and prevents its rupture. A flow diverter can be used, but risks complications.
Aortic and peripheral
For aneurysms in the aorta, arms, legs, or head, the weakened section of the vessel may be replaced by a bypass graft that is sutured at the vascular stumps. Instead of sewing, the graft tube ends, made rigid and expandable by nitinol wireframe, can be easily inserted in its reduced diameter into the vascular stumps and then expanded up to the most appropriate diameter and permanently fixed there by external ligature. New devices were recently developed to substitute the external ligature by expandable ring allowing use in acute ascending aorta dissection, providing airtight (i.e. not dependent on the coagulation integrity), easy and quick anastomosis extended to the arch concavity Less invasive endovascular techniques allow covered metallic stent grafts to be inserted through the arteries of the leg and deployed across the aneurysm.
Renal
Renal aneurysms are very rare consisting of only 0.1–0.09% while rupture is even more rare. Conservative treatment with control of concomitant hypertension being the primary option with aneurysms smaller than 3 cm. If symptoms occur, or enlargement of the aneurysm, then endovascular or open repair should be considered. Pregnant women (due to high rupture risk of up to 80%) should be treated surgically. | Aneurysm | Wikipedia | 401 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Epidemiology
Incidence rates of cranial aneurysms are estimated at between 0.4% and 3.6%. Those without risk factors have expected prevalence of 2–3%. In adults, females are more likely to have aneurysms. They are most prevalent in people ages 35 – 60 but can occur in children as well. Aneurysms are rare in children with a reported prevalence of .5% to 4.6%. The most common incidence is among 50-year-olds, and there are typically no warning signs. Most aneurysms develop after the age of 40.
Pediatric aneurysms
Pediatric aneurysms have different incidences and features than adult aneurysms. Intracranial aneurysms are rare in childhood, with over 95% of all aneurysms occurring in adults.
Risk factors
Incidence rates are two to three times higher in males, while there are more large and giant aneurysms and fewer multiple aneurysms. Intracranial hemorrhages are 1.6 times more likely to be due to aneurysms than cerebral arteriovenous malformations in whites, but four times less in certain Asian populations.
Most patients, particularly infants, present with subarachnoid hemorrhage and corresponding headaches or neurological deficits. The mortality rate for pediatric aneurysms is lower than in adults.
Modeling | Aneurysm | Wikipedia | 292 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Modeling of aneurysms consists of creating a 3D model that mimics a particular aneurysm. Using patient data for the blood velocity, and blood pressure, along with the geometry of the aneurysm, researchers can apply computational fluid dynamics (CFD) to predict whether an aneurysm is benign or if it is at risk of complication. One risk is rupture. Analyzing the velocity and pressure profiles of the blood flow leads to obtaining the resulting wall shear stress on the vessel and aneurysm wall. The neck of the aneurysm is the most at risk due to the combination of a small wall thickness and high wall shear stress. When the wall shear stress reaches its limit, the aneurysm ruptures, leading to intracranial hemorrhage. Conversely, another risk of aneurysms is the creation of clots. Aneurysms create a pocket which diverts blood flow. This diverted blood flow creates a vortex inside of the aneurysm. This vortex can lead to areas inside of the aneurysm where the blood flow is stagnant, which promotes formations of clots. Blood clots can dislodge from the aneurysm, which can then lead to an embolism when the clot gets stuck and disrupts blood flow. Model analysis allows these risky aneurysms to be identified and treated. | Aneurysm | Wikipedia | 290 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
In the past, aneurysms were modeled as rigid spheres with linear inlets and outlets. As technology advances, the ability to detect and analyze aneurysms becomes easier. Researchers are able to CT scan a patient's body to create a 3D computer model that possesses the correct geometry. Aneurysms can now be modeled with their distinctive "balloon" shape. Nowadays researchers are optimizing the parameters required to accurately model a patient's aneurysm that will lead to a successful intervention. Current modeling is not able to take into account all variables though. For example, blood is considered to be a non-Newtonian fluid. Some researchers treat blood as a Newtonian fluid instead, as it sometimes has negligible effects to the analysis in large vessels. When analyzing small vessels though, such as those present in intracranial aneurysms. Similarly, sometimes it is difficult to model the varying wall thickness in small vessels, so researchers treat wall thickness as constant. Researchers make these assumptions to reduce computational time. Nonetheless, making erroneous assumptions could lead to a misdiagnosis that could put a patient's life at risk.
Notable cases | Aneurysm | Wikipedia | 238 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
U.S. Senator Joe Biden, who later became President, had two brain aneurysms in 1988. He recovered after successful surgeries to correct them.
Lucille Ball died from an aortic rupture in the abdominal area days after having undergone apparently successful heart surgery for a dissecting aortic aneurysm.
Laura Branigan died of a cerebral aneurysm.
David Cone had an aneurysm and missed most of the 1996 baseball season.
Davie Cooper died in 1995 following a subarachnoid hemorrhage whilst filming a football television series.
John Olerud had an aneurysm in 1989 and has worn a batting helmet on the field all of his career since then.
Albert Einstein died from a repaired aortic aneurysm.
Thomas Mikal Ford died from a ruptured aneurysm in his abdomen at age 52.
Charles de Gaulle died from a ruptured aneurysm within his neck.
Richard Holbrooke died from a thoracic aortic aneurysm.
Édith Piaf died from an aneurysm due to liver failure.
Stuart Sutcliffe died from an aneurysm in his brain's right hemisphere.
Raymond F. Boyce died in 1974 as a result of an aneurysm.
John Ritter died in 2003 of a misdiagnosed thoracic aortic dissection (aortic aneurysm).
Isabel Granada died of a cerebral aneurysm.
Geoffrey Thompson died of a brain aneurysm at his daughter's wedding, hosted at his theme park, Blackpool Pleasure Beach.
Edwin Rosario died of an aneurysm in 1997.
Joni Mitchell had a brain aneurysm in 2015 and survived.
Grant Imahara died from a brain aneurysm in July 2020.
Dr. Dre had a brain aneurysm in January 2021.
Jovit Baldivino died from a brain aneurysm in December 2022.
Tom Sizemore died from a brain aneurysm in March 2023. | Aneurysm | Wikipedia | 434 | 322553 | https://en.wikipedia.org/wiki/Aneurysm | Biology and health sciences | Injury | null |
Trionychidae is a family of turtles, commonly known as softshell turtles or simply softshells. The family was described by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can adapt to living in highly brackish waters. Members of this family occur in Africa, Asia, and North America, with extinct species known from Australia. Most species have traditionally been included in the genus Trionyx, but the vast majority have since been moved to other genera. Among these are the North American Apalone softshells that were placed in Trionyx until 1987.
Characteristics
Turtles of the family Trionychidae are called "softshell" because their carapaces lack horny scutes (scales), though the spiny softshell, Apalone spinifera, does have some scale-like projections, to which its common name refers. The carapace is leathery and pliable, particularly at the sides. The central part of the carapace has a layer of solid bone beneath it, as in other turtles, but this is absent at the outer edges. Some species also have dermal bones in the plastron, but these are not attached to the bones of the shell. The light and flexible shell of these turtles allows them to move more easily in open water or in muddy lake bottoms. Having a soft shell also allows them to move much faster on land than most turtles. Their feet are webbed and three-clawed, hence the family name "Trionychidae," which means "three-clawed". The carapace color of each type of softshell turtle tends to match the sand or mud color of its geographical region, assisting in their "lie in wait" feeding methodology.
These turtles have many characteristics pertaining to their aquatic lifestyle. Many must be submerged in order to swallow their food. They have elongated, soft, snorkel-like nostrils. Their necks are disproportionately long in comparison to their body sizes, enabling them to breathe surface air while their bodies remain submerged in the substrate (mud or sand) a foot or more below the surface.
Females can grow up to several feet in carapace diameter, while males stay much smaller; this is their main form of sexual dimorphism. Pelochelys cantorii, found in southeastern Asia, is the largest softshell turtle. | Trionychidae | Wikipedia | 497 | 322562 | https://en.wikipedia.org/wiki/Trionychidae | Biology and health sciences | Turtles | Animals |
Most are strict carnivores, with diets consisting mainly of fish, aquatic crustaceans, snails, amphibians, and sometimes birds and small mammals.
Softshells are able to "breathe" underwater with rhythmic movements of their mouth cavity, which contains numerous processes copiously supplied with blood, acting similarly to gill filaments in fish. This enables them to stay underwater for prolonged periods. Moreover, the Chinese softshell turtle has been shown to excrete urea while "breathing" underwater; this is an efficient solution when the animal does not have access to fresh water, e.g., in brackish-water environments.
According to Ditmars (1910): "The mandibles of many species form the outer border of powerful crushing processes—the alveolar surfaces of the jaws", which aids the ingestion of tough prey such as molluscs. These jaws make large turtles dangerous, as they are capable of amputating a person's finger, or possibly their hand.
Unlike the temperature-dependent sex determination of most turtles, Trionychids have ZZ/ZW genetic sex determination; microchromosomes play a role in determining sex.
As food
In East Asia
Softshell turtles are eaten as a delicacy in most parts of their range, particularly in East Asia. A Chinese dish stews them with chicken. According to a 1930 report by Soame Jenyns, Guangdong restaurants had them imported from Guangxi in large numbers; "eaten stewed with almonds, roast with chili sauce or fried with bamboo shoots, they [were] considered a great delicacy."
Worldwide, the most commonly consumed softshell species is the Chinese softshell Pelodiscus sinensis. As a noted Japanese biologist pointed out in 1904, the Japanese variety of this turtle, which at time was classified as Trionyx japonicus, occupied a place in Japanese cuisine as esteemed as the diamondback terrapin in the United States or the green turtle in England. The farming of this "luscious reptile", known in Japan as suppon, was already developed on an industrial scale in that country by the late 19th century. | Trionychidae | Wikipedia | 456 | 322562 | https://en.wikipedia.org/wiki/Trionychidae | Biology and health sciences | Turtles | Animals |
Due to rising demand and overhunting, the price of Pelodiscus sinensis in China skyrocketed by the mid-1990s; large-scale turtle farming in China and neighboring countries; raising this species by hundreds of millions was the response, with prices soon returning to a more affordable level. Another species, Palea steindachneri, is farmed in China, as well, but on a much smaller scale (with farm herds measured in hundreds of thousands, rather than hundreds of millions).
In the United States
In the United States, harvesting softshells (e.g. Apalone ferox) was, until recently, legal in Florida. Environmental groups have been advocating the authorities' banning or restricting the practice. The Florida Fish and Wildlife Conservation Commission responded by introducing the daily limit of 20 turtles for licensed harvesters—a level which the turtle advocates consider unsustainable, as there may be between 100 and 500 hunters statewide. While some catch was consumed locally, most was exported; the Commission estimated (2008) around 3,000 pounds of softshell turtles were exported to China each week via Tampa International Airport.
New rules, in effect as of July 20, 2009, restrict collecting any wild turtles to one turtle per person per day, completely prohibit collection of softshells (Apalone) in May through July, and prohibit trade in turtles caught from the wild. An exemption is provided for licensed turtle farms that need to catch turtles in the wild to serve as their breeding stock.
Some other US states, too, have already adopted strict limitations on wild turtle trade. In 2009, South Carolina passed a law (Bill H.3121) restricting interstate and international export of wild-caught turtles (both soft-shell and some other species) to 10 turtles per person at one time, and 20 turtles per person per year.
Taxonomy
Family Trionychidae
Palaeotrionyx (fossil) Paleotrionyx jimenezfuentesi
Subfamily Plastomeninae (fossil)
Genus Gilmoremys
Genus Hutchemys
Genus Plastomenus
Subfamily Cyclanorbinae
Genus Cyclanorbis
Genus Cycloderma
Genus Lissemys
Subfamily Trionychinae
Genus Amyda, Amyda menneri
Genus Apalone
Genus Chitra, Chitra minor
Genus Dogania
Genus Nilssonia
Genus Palea
Genus Pelochelys
Genus Pelodiscus
Genus Rafetus
Genus Trionyx
Past classification
Genus Aspideretes | Trionychidae | Wikipedia | 504 | 322562 | https://en.wikipedia.org/wiki/Trionychidae | Biology and health sciences | Turtles | Animals |
Phylogeny
The following cladogram shows the relationships among the species:
Gallery | Trionychidae | Wikipedia | 17 | 322562 | https://en.wikipedia.org/wiki/Trionychidae | Biology and health sciences | Turtles | Animals |
The leatherback sea turtle (Dermochelys coriacea), sometimes called the lute turtle, leathery turtle or simply the luth, is the largest of all living turtles and the heaviest non-crocodilian reptile, reaching lengths of up to and weights of . It is the only living species in the genus Dermochelys and family Dermochelyidae. It can easily be differentiated from other modern sea turtles by its lack of a bony shell; instead, its carapace is covered by oily flesh and flexible, leather-like skin, for which it is named. Leatherback turtles have a global range, although there are multiple distinct subpopulations. The species as a whole is considered vulnerable, and some of its subpopulations are critically endangered.
Taxonomy and evolution
Taxonomy
Dermochelys coriacea is the only species in genus Dermochelys. The genus, in turn, contains the only extant member of the family Dermochelyidae.
Domenico Agostino Vandelli named the species first in 1761 as Testudo coriacea after an animal captured at Ostia and donated to the University of Padua by Pope Clement XIII. In 1816, French zoologist Henri Blainville coined the term Dermochelys. The leatherback was then reclassified as Dermochelys coriacea. In 1843, the zoologist Leopold Fitzinger put the genus in its own family, Dermochelyidae. In 1884, the American naturalist Samuel Garman described the species as Sphargis coriacea schlegelii. The two were then united in D. coriacea, with each given subspecies status as D. c. coriacea and D. c. schlegelii. The subspecies were later labeled invalid synonyms of D. coriacea.
Both the turtle's common and scientific names come from the leathery texture and appearance of its carapace (Dermochelys coriacea literally translates to "Leathery Skin-turtle"). Older names include "leathery turtle" and "trunk turtle". The common names incorporating "lute" and "luth" compare the seven ridges that run the length of the animal's back to the seven strings on the musical instrument of the same name. But probably more accurately derived from the lute's ribbed back which is in the form of a shell. | Leatherback sea turtle | Wikipedia | 494 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Evolution
Relatives of modern leatherback turtles have existed in relatively the same form since the first true sea turtles evolved over 110 million years ago during the Cretaceous period. The dermochelyids are relatives of the family Cheloniidae, which contains the other six extant sea turtle species. However, their sister taxon is the extinct family Protostegidae that included other species that did not have a hard carapace.
Anatomy and physiology
Leatherback turtles have the most hydrodynamic body of any sea turtle, with a large, teardrop-shaped body. A large pair of front flippers powers the turtles through the water. Like other sea turtles, the leatherback has flattened forelimbs adapted for swimming in the open ocean. Claws are absent from both pairs of flippers. The leatherback's flippers are the largest in proportion to its body among extant sea turtles. Leatherback's front flippers can grow up to in large specimens, the largest flippers (even in comparison to its body) of any sea turtle.
The leatherback has several characteristics that distinguish it from other sea turtles. Its most notable feature is the lack of a bony carapace. Instead of scutes, it has thick, leathery skin with embedded minuscule osteoderms. Seven distinct ridges rise from the carapace, crossing from the cranial to caudal margin of the turtle's back. Leatherbacks are unique among reptiles in that their scales lack β-keratin. The entire turtle's dorsal surface is colored dark grey to black, with a scattering of white blotches and spots. Demonstrating countershading, the turtle's underside is lightly colored. Instead of teeth, the leatherback turtle has points on the tomium of its upper lip, with backwards spines in its throat (esophagus) to help it swallow food and to stop its prey from escaping once caught. | Leatherback sea turtle | Wikipedia | 385 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
D. coriacea adults average in curved carapace length (CCL), in total length, and in weight. In the Caribbean, the mean size of adults was reported at in weight and in CCL. Similarly, those nesting in French Guiana, weighed an average of and measured in CCL. The largest verified specimen ever found was discovered on the Pakistani beach of Sandspit and measured in CCL and in weight. A previous contender, the "Harlech turtle", was purportedly in CCL and in weight, however recent inspection of its remains housed at the National Museum Cardiff have found that its true CCL is closer to , casting doubt on the accuracy of the claimed weight, as well. On the other hand, one scientific paper has claimed that the species can weigh up to without providing more verifiable detail. The leatherback turtle is scarcely larger than any other sea turtle upon hatching, as they average in carapace length and weigh around when freshly hatched.
D. coriacea exhibits several anatomical characteristics believed to be associated with a life in cold waters, including an extensive covering of brown adipose tissue, temperature-independent swimming muscles, countercurrent heat exchangers between the large front flippers and the core body, and an extensive network of countercurrent heat exchangers surrounding the trachea.
Mechanical properties
The carapace of the leatherback sea turtle has a unique design which enables the sea turtles to withstand high hydrostatic pressures as they dive to depths of 1200 m. Unlike other sea turtles, the leatherback sea turtle has a soft, leathery skin which covers the osteoderms rather than a hard keratinous shell. The osteoderms are made up of bone-like hydroxyapatite/collagen tissue and have jagged edges, referred to as teeth. These osteoderms are connected by a configuration of interpenetrating extremities called sutures that provide flexibility to the carapace, enabling in plane and out of plane movement between osteoderms. This is important since the lungs, and thus the carapace, expand when taking in air and contract when deep diving. | Leatherback sea turtle | Wikipedia | 441 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
The sutures connect rigid elements and flexible joints in a zig-zag configuration, so there is no region where teeth can easily penetrate the carapace. There are two main failure mechanisms for the tires in tension: tooth failure corresponding to mineral-brittle failure; and interfacial failure between teeth corresponding to collagen-ductile failure. The triangular tooth geometry is able to evenly distribute load and absorb energy. This leads to a high strength in tension since this geometry takes advantage of the tensile strength of bone and the interface. Additionally, the carapace is tough because sutures prevent crack propagation. Under load, cracks interact with the sutures which can resist crack growth via crack bridging. This phenomenon was observed in sequential compression of osteoderm samples.
Physiology
Leatherbacks have been viewed as unique among extant non-avian reptiles for their ability to maintain high body temperatures using metabolically generated heat, or endothermy. Initial studies on their metabolic rates found leatherbacks had resting metabolisms around three times higher than expected for reptiles of their size. However, recent studies using reptile representatives encompassing all the size ranges leatherbacks pass through during ontogeny discovered the resting metabolic rate of a large D. coriacea is not significantly different from predicted results based on allometry.
Rather than using a high resting metabolism, leatherbacks appear to take advantage of a high activity rate. Studies on wild D. coriacea discovered individuals may spend as little as 0.1% of the day resting. This constant swimming creates muscle-derived heat. Coupled with their countercurrent heat exchangers, insulating fat covering, and large size, leatherbacks are able to maintain high temperature differentials compared to the surrounding water. Adult leatherbacks have been found with core body temperatures that were above the water in which they were swimming.
Leatherback turtles are one of the deepest-diving marine animals. Individuals have been recorded diving to depths as great as .
Typical dive durations are between 3 and 8 minutes, with dives of 30–70 minutes occurring infrequently.
They are also the fastest-moving non-avian reptiles. The 1992 edition of the Guinness Book of World Records lists the leatherback turtle moving at in the water. More typically, they swim at . | Leatherback sea turtle | Wikipedia | 463 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Distribution
The leatherback turtle is a species with a cosmopolitan global range. Of all the extant sea turtle species, D. coriacea has the widest distribution, reaching as far north as Alaska and Norway and as far south as Cape Agulhas in Africa and the southernmost tip of New Zealand. The leatherback is found in all tropical and subtropical oceans, and its range extends well into the Arctic Circle.
The three major, genetically distinct populations occur in the Atlantic, eastern Pacific, and western Pacific Oceans. While nesting beaches have been identified in the region, leatherback populations in the Indian Ocean remain generally unassessed and unevaluated.
Recent estimates of global nesting populations are that 26,000 to 43,000 females nest annually, which is a dramatic decline from the 115,000 estimated in 1980.
Atlantic subpopulation
The leatherback turtle population in the Atlantic Ocean ranges across the entire region. They range as far north as the North Sea and to the Cape of Good Hope in the south. Unlike other sea turtles, leatherback feeding areas are in colder waters, where an abundance of their jellyfish prey is found, which broadens their range. However, only a few beaches on both sides of the Atlantic provide nesting sites.
Off the Atlantic coast of Canada, leatherback turtles feed in the Gulf of Saint Lawrence near Quebec and as far north as Newfoundland and Labrador. The most significant Atlantic nesting sites are in Suriname, Guyana, French Guiana in South America, Antigua and Barbuda, and Trinidad and Tobago in the Caribbean, and Gabon in Central Africa. The beaches of Mayumba National Park in Mayumba, Gabon, host the largest nesting population on the African continent and possibly worldwide, with nearly 30,000 turtles visiting its beaches each year between October and April. Off the northeastern coast of the South American continent, a few select beaches between French Guiana and Suriname are primary nesting sites of several species of sea turtles, the majority being leatherbacks. A few hundred nest annually on the eastern coast of Florida. In Costa Rica, the beaches of Gandoca and Parismina provide nesting grounds. | Leatherback sea turtle | Wikipedia | 423 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Pacific subpopulation
Pacific leatherbacks divide into two populations. One population nests on beaches in Papua, Indonesia, and the Solomon Islands, and forages across the Pacific in the Northern Hemisphere, along the coasts of California, Oregon, and Washington in North America. The eastern Pacific population forages in the Southern Hemisphere, in waters along the western coast of South America, nesting in Mexico, Panama, El Salvador, Nicaragua, and Costa Rica, as well as eastern Australia.
The continental United States offers two major Pacific leatherback feeding areas. One well-studied area is just off the northwestern coast near the mouth of the Columbia River. The other American area is located in California. Further north, off the Pacific coast of Canada, leatherbacks visit the beaches of British Columbia.
Estimates by the WWF suggest only 2,300 adult females of the Pacific leatherback remain, making it the most endangered marine turtle subpopulation.
South China Sea subpopulation
A third possible Pacific subpopulation has been proposed, those that nest in Malaysia. This subpopulation, however, has effectively been eradicated. The beach of Rantau Abang in Terengganu, Malaysia, once had the largest nesting population in the world, hosting 10,000 nests per year. The major cause of the decline was egg consumption by humans. Conservation efforts initiated in the 1960s were ineffective because they involved excavating and incubating eggs at artificial sites which inadvertently exposed the eggs to high temperatures. It only became known in the 1980s that sea turtles undergo temperature-dependent sex determination; it is suspected that nearly all the artificially incubated hatchlings were female. In 2008, two turtles nested at Rantau Abang, and unfortunately, the eggs were infertile. Additionally, there are small nesting sites in southern Thailand where 18 turtles nested in 2021.
Indian Ocean subpopulation
While little research has been done on Dermochelys populations in the Indian Ocean, nesting populations are known from Sri Lanka and the Nicobar Islands. These turtles are proposed to form a separate, genetically distinct Indian Ocean subpopulation.
Ecology and life history | Leatherback sea turtle | Wikipedia | 428 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Habitat
Leatherback sea turtles can be found primarily in the open ocean. Scientists tracked a leatherback turtle that swam from Jen Womom beach of Tambrauw Regency in West Papua of Indonesia to the US in a foraging journey over a period of 647 days. Leatherbacks follow their jellyfish prey throughout the day, resulting in turtles "preferring" deeper water in the daytime, and shallower water at night (when the jellyfish rise up the water column). This hunting strategy often places turtles in very frigid waters. One individual was found actively hunting in waters where temperatures were as low as . Following each foraging dive, the leatherback would return to warmer () surface waters to regain body heat before continuing to dive into near freezing waters. Leatherback turtles are known to pursue prey deeper than 1000 m—beyond the physiological limits of all other diving tetrapods except for beaked whales and sperm whales.
Their favored breeding beaches are mainland sites facing the deep water, and they seem to avoid those sites protected by coral reefs.
Feeding
Adult D. coriacea turtles subsist almost entirely on jellyfish. Due to their obligate feeding nature, leatherbacks help control jellyfish populations. Leatherbacks also feed on other soft-bodied organisms, such as other cnidarians (siphonophores), tunicates (salps and pyrosomas) and cephalopods (squid). They are also believed to feed on small crustaceans (amphipods and crabs), fish (possibly symbiotes with jellies), sea urchins, snails, seagrasses, and algae.
Pacific leatherbacks migrate about across the Pacific from their nesting sites in Indonesia to eat California jellyfish. During these long traveling periods, Remora remora (common Remoras) will latch onto leatherbacks and display phoresis behavior or 'hitchhiking' this represents commensalism, where one species is benefiting, while the other species is not gaining or losing anything. One cause for their endangered state is plastic bags floating in the ocean. Pacific leatherback sea turtles mistake these plastic bags for jellyfish; an estimated one-third of adults have ingested plastic. Plastic enters the oceans along the west coast of urban areas, where leatherbacks forage, with Californians using upward of 19 billion plastic bags every year. Plastic bags were banned in California in 2016. | Leatherback sea turtle | Wikipedia | 490 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Several species of sea turtles commonly ingest plastic marine debris, and even small quantities of debris can kill sea turtles by obstructing their digestive tracts. Nutrient dilution, which occurs when plastics displace food in the gut, affects the nutrient gain and consequently the growth of sea turtles. Ingestion of marine debris and slowed nutrient gain leads to increased time for sexual maturation that may affect future reproductive behaviors. These turtles have the highest risk of encountering and ingesting plastic bags offshore of San Francisco Bay, the Columbia River mouth, and Puget Sound.
Lifespan
Very little is known of the species' lifespan. Some reports claim "30 years or more", while others state "50 years or more" and upper estimates exceed 100 years.
In 2020, researchers from CSIRO, Australia's National Science Agency, developed a method to calculate the natural lifespan of vertebrate animals by leveraging genetic markers and known lifespans of various species. From the genomic sequencing of DNA samples taken from five different marine turtle species, the natural lifespan of the Leatherback turtle was calculated at 90.4 years.
Death and decomposition
Dead leatherbacks that wash ashore are microecosystems while decomposing. In 1996, a drowned carcass held sarcophagid and calliphorid flies after being picked open by a pair of Coragyps atratus vultures. Infestation by carrion-eating beetles of the families Scarabaeidae, Carabidae, and Tenebrionidae soon followed. After days of decomposition, beetles from the families Histeridae and Staphylinidae and anthomyiid flies invaded the corpse, as well. Organisms from more than a dozen families took part in consuming the carcass.
Life history | Leatherback sea turtle | Wikipedia | 361 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Predation
Leatherback turtles face many predators in their early lives. Eggs may be preyed on by a diversity of coastal predators, including ghost crabs, monitor lizards, raccoons, coatis, dogs, coyotes, genets, mongooses, and shorebirds ranging from small plovers to large gulls. Many of the same predators feed on baby turtles as they try to get to the ocean, as well as frigatebirds and varied raptors. Once in the ocean, young leatherbacks face predation from cephalopods, requiem sharks, and various large fish. Despite their lack of a hard shell, the huge adults face fewer serious predators, though they are occasionally overwhelmed and preyed on by very large marine predators such as killer whales, great white sharks, and tiger sharks. Nesting females have been preyed upon by jaguars in the American tropics. Nesting females in Papua New Guinea are also attacked by saltwater crocodiles.
The adult leatherback has been observed aggressively defending itself at sea from predators. A medium-sized adult was observed chasing a shark that had attempted to bite it and then turned its aggression and attacked the boat containing the humans observing the prior interaction. Dermochelys juveniles spend more of their time in tropical waters than do adults.
Adults are prone to long-distance migration. Migration occurs between the cold waters where mature leatherbacks feed, to the tropical and subtropical beaches in the regions where they hatch. In the Atlantic, females tagged in French Guiana have been recaptured on the other side of the ocean in Morocco and Spain.
Mating
Mating takes place at sea. Males never leave the water once they enter it, unlike females, which nest on land. After encountering a female (which possibly exudes a pheromone to signal her reproductive status), the male uses head movements, nuzzling, biting, or flipper movements to determine her receptiveness. Males can mate every year but the females mate every two to three years. Fertilization is internal, and multiple males usually mate with a single female. This polyandry does not provide the offspring with any special advantages.
Female leatherbacks are known to nest up to 10 times in a single nesting season giving them the shortest internesting interval of all sea turtles.
Offspring | Leatherback sea turtle | Wikipedia | 458 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
While other sea turtle species almost always return to their hatching beach, leatherbacks may choose another beach within the region. They choose beaches with soft sand because their softer shells and plastrons are easily damaged by hard rocks. Nesting beaches also have shallower approach angles from the sea. This is a vulnerability for the turtles because such beaches easily erode. They nest at night when the risk of predation and heat stress is lowest. As leatherback turtles spend the vast majority of their lives in the ocean, their eyes are not well adapted to night vision on land. The typical nesting environment includes a dark forested area adjacent to the beach. The contrast between this dark forest and the brighter, moonlit ocean provides directionality for the females. They nest towards the dark and then return to the ocean and the light. The mean time it takes to complete a nesting event from landing to departure is 108.1 minutes.
Females excavate a nest above the high-tide line with their flippers. One female may lay as many as nine clutches in one breeding season. About nine days pass between nesting events. Average clutch size is around 110 eggs, 85% of which are viable. After laying, the female carefully back-fills the nest, disguising it from predators with a scattering of sand. With the average clutch size being around 110, around 50 percent of the eggs do not even develop into hatchlings. This only causes more concern for the species, because it makes management much harder to determine.
Development of offspring
Cleavage of the cell begins within hours of fertilization, but development is suspended during the gastrulation period of movements and infoldings of embryonic cells, while the eggs are being laid. Development then resumes, but embryos remain extremely susceptible to movement-induced mortality until the membranes fully develop after incubating for 20 to 25 days. The structural differentiation of body and organs (organogenesis) soon follows. The eggs hatch in about 60 to 70 days. As with other reptiles, the nest's ambient temperature determines the sex of the hatchings. After nightfall, the hatchings dig to the surface and walk to the sea. The morphology of offspring has been found to vary with nest incubation temperatures. Higher temperatures resulted in lower mass, smaller appendages, narrower carapace widths, and shorter flipper lengths while lower temperatures resulted in greater mass, wider appendage widths, wider carapace widths, and longer flipper lengths. | Leatherback sea turtle | Wikipedia | 502 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Leatherback nesting seasons vary by location; it occurs from February to July in Parismina, Costa Rica. Farther east in French Guiana, nesting is from March to August. Atlantic leatherbacks nest between February and July from South Carolina in the United States to the United States Virgin Islands in the Caribbean and to Suriname and Guyana.
Importance to humans
People around the world still harvest sea turtle eggs. Asian exploitation of turtle nests has been cited as the most significant factor for the species' global population decline. In Southeast Asia, egg harvesting in countries such as Thailand and Malaysia has led to a near-total collapse of local nesting populations. In Malaysia, where the turtle is practically locally extinct, the eggs are considered a delicacy. In the Caribbean, some cultures consider the eggs to be aphrodisiacs.
They are also a major jellyfish predator, which helps keep populations in check. This bears importance to humans, as jellyfish diets consist largely of larval fish, the adults of which are commercially fished by humans.
Cultural significance
The turtle is known to be of cultural significance to tribes all over the world. The Seri people, from the Mexican state of Sonora, find the leatherback sea turtle culturally significant because it is one of their five main creators. The Seri people devote ceremonies and fiestas to the turtle when one is caught and then released back into the environment. The Seri people have noticed the drastic decline in turtle populations over the years and created a conservation movement to help this. The group, made up of both youth and elders from the tribe, is called Grupo Tortuguero Comaac. They use both traditional ecological knowledge and Western technology to help manage the turtle populations and protect the turtle's natural environment.
In the Malaysian state of Terengganu, the turtle is the state's main animal and is usually seen in tourism ads.
On the South Island of New Zealand's Banks Peninsula the leatherback turtle has great spiritual significance to the Koukourārata hapū of te Rūnanga o Ngāi Tahu, as well as wider significance in Te Ao Māori and to the peoples of greater Polynesia according to the protocols of each rohe. In 2021, a leatherback sea turtle was laid to rest by New Zealand's Department of Conservation in a hilltop cave on the Peninsula's Horomaka Island dug by hapū and in accordance with their rohe's ley lines, according to New Zealand's state broadcaster, Radio New Zealand. | Leatherback sea turtle | Wikipedia | 503 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Conservation
Leatherback turtles have few natural predators once they mature; they are most vulnerable to predation in their early life stages. Birds, small mammals, and other opportunists dig up the nests of turtles and consume eggs. Shorebirds and crustaceans prey on the hatchlings scrambling for the sea. Once they enter the water, they become prey to predatory fish and cephalopods.
Leatherbacks have slightly fewer human-related threats than other sea turtle species, however, turtle-fishery interactions may play a larger role than previously recognized. Their flesh contains too much oil and fat to be considered palatable, reducing the demand. However, human activity still endangers leatherback turtles in direct and indirect ways. Directly, a few are caught for their meat by subsistence fisheries. Nests are raided by humans in places such as Southeast Asia. In the state of Florida, there have been 603 leatherback strandings between 1980 and 2014. Almost one-quarter (23.5%) of leatherback strandings are due to vessel-strike injuries, which is the highest cause of strandings.
Light pollution is a serious threat to sea turtle hatchlings which have a strong attraction to light. Human-generated light from streetlights and buildings causes hatchlings to become disoriented, crawling toward the light and away from the beach. Hatchlings are attracted to light because the lightest area on a natural beach is the horizon over the ocean, the darkest area is the dunes or forest. On Florida's Atlantic coast, some beaches with high turtle nesting density have lost thousands of hatchlings due to artificial light. | Leatherback sea turtle | Wikipedia | 326 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Many human activities indirectly harm Dermochelys populations. As a pelagic species, D. coriacea is occasionally caught as bycatch. Entanglement in lobster pot ropes is another hazard the animals face. As the largest living sea turtles, turtle excluder devices can be ineffective with mature adults. In the eastern Pacific alone, a reported average of 1,500 mature females were accidentally caught annually in the 1990s. Pollution, both chemical and physical, can also be fatal. Many turtles die from malabsorption and intestinal blockage following the ingestion of balloons and plastic bags which resemble their jellyfish prey. Chemical pollution also has an adverse effect on Dermochelys. A high level of phthalates has been measured in their eggs' yolks. Leatherback sea turtles ranging from 1885 to 2007 were autopsied for the existence of plastic in the gastrointestinal tract. It was discovered that 34% of the cases had plastic blockage.
Due to their diet consisting of gelatinous zooplankton, the leatherback sea turtle consumes high amounts of salt. Different life stages of dead individuals from the western Atlantic Ocean were used to test the concentrations of various contaminants found in the salt glands and red blood cells. These contaminants include arsenic, cadmium, lead, mercury, and selenium. The contaminants were found in higher concentrations in the blood compared to the salt gland secretions. The length of the curve in the carapace of a turtle had a direct correlation with cadmium and mercury concentrations. Salt glands and red blood cells are potentially susceptible to high levels of contaminants being found in the oceans.
Global initiatives
D. coriacea is listed on CITES Appendix I, which makes export/import of this species (including parts) illegal. It has been listed as an EDGE species by the Zoological Society of London.
The species is listed in the IUCN Red List of Threatened Species as VU (Vulnerable), and additionally with the following infraspecific taxa assessments:
East Pacific Ocean subpopulation: CR (Critically Endangered)
Northeast Indian Ocean subpopulation: DD (Data Deficient)
Northwest Atlantic Ocean subpopulation: EN (Endangered)
Southeast Atlantic Ocean subpopulation: DD (Data Deficient)
Southwest Atlantic Ocean subpopulation CR (Critically Endangered)
Southwest Indian Ocean subpopulation CR (Critically Endangered)
West Pacific Ocean subpopulation CR (Critically Endangered) | Leatherback sea turtle | Wikipedia | 502 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Conserving Pacific and Eastern Atlantic populations were included among the top-ten issues in turtle conservation in the first State of the World's Sea Turtles report published in 2006. The report noted significant declines in the Mexican, Costa Rican, and Malaysian populations. The eastern Atlantic nesting population was threatened by increased fishing pressures from eastern South American countries.
The Leatherback Trust was founded specifically to conserve sea turtles, specifically its namesake. The foundation established a sanctuary in Costa Rica, the Parque Marino Las Baulas.
National and local initiatives
The leatherback sea turtle is subject to different conservation laws in various countries.
The United States listed it as an endangered species on 2 June 1970. The passing of the Endangered Species Act of 1973 ratified its status. In 2012, the National Oceanic and Atmospheric Administration designated 41,914 square miles of Pacific Ocean along California, Oregon, and Washington as "critical habitat". In Canada, the Species at Risk Act made it illegal to exploit the species in Canadian waters. The Committee on the Status of Endangered Wildlife in Canada classified it as endangered. Ireland and Wales initiated a joint leatherback conservation effort between Swansea University and University College Cork. Funded by the European Regional Development Fund, the Irish Sea Leatherback Turtle Project focuses on research such as tagging and satellite tracking of individuals.
Earthwatch Institute, a global nonprofit that teams volunteer with scientists to conduct important environmental research, launched a program called "Trinidad's Leatherback Sea Turtles". This program strives to help save the world's largest turtle from extinction in Matura Beach, Trinidad, as volunteers work side by side with leading scientists and a local conservation group, Nature Seekers. This tropical island off the coast of Venezuela is known for its vibrant ethnic diversity and rich cultural events. It is also the site of one of the most important nesting beaches for endangered leatherback turtles, enormous reptiles that can weigh a ton and dive deeper than many whales. Each year, more than 2,000 female leatherbacks haul themselves onto Matura Beach to lay their eggs. With leatherback populations declining more quickly than any other large animal in modern history, each turtle is precious. On this research project, Dennis Sammy of Nature Seekers and Scott Eckert of Wider Caribbean Sea Turtle Conservation Network work alongside a team of volunteers to help prevent the extinction of leatherback sea turtles. | Leatherback sea turtle | Wikipedia | 467 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Several Caribbean countries started conservation programs, such as the St. Kitts Sea Turtle Monitoring Network, focused on using ecotourism to highlight the leatherback's plight. On the Atlantic coast of Costa Rica, the village of Parismina has one such initiative. Parismina is an isolated sandbar where a large number of leatherbacks lay eggs, but poachers abound. Since 1998, the village has been assisting turtles with a hatchery program. The Parismina Social Club is a charitable organization backed by American tourists and expatriates, which collects donations to fund beach patrols. In Dominica, patrollers from DomSeTCo protect leatherback nesting sites from poachers.
Mayumba National Park in Gabon, Central Africa, was created to protect Africa's most important nesting beach. More than 30,000 turtles nest on Mayumba's beaches between September and April each year.
In mid-2007, the Malaysian Fisheries Department revealed a plan to clone leatherback turtles to replenish the country's rapidly declining population. Some conservation biologists, however, are skeptical of the proposed plan because cloning has only succeeded on mammals such as dogs, sheep, cats, and cattle, and uncertainties persist about cloned animals' health and lifespans. Leatherbacks used to nest in the thousands on Malaysian beaches, including those at Terengganu, where more than 3,000 females nested in the late 1960s. The last official count of nesting leatherback females on that beach was recorded to be a mere two females in 1993.
In Brazil, reproduction of the leatherback turtle is being assisted by the Brazilian Institute of Environment and Renewable Natural Resources' projeto TAMAR (TAMAR project), which works to protect nests and prevent accidental kills by fishing boats. The last official count of nesting leatherback females in Brazil yielded only seven females. In January 2010, one female at Pontal do Paraná laid hundreds of eggs. Since leatherback sea turtles had been reported to nest only at Espírito Santo's shore, but never in the state of Paraná, this unusual act brought much attention to the area, biologists have been protecting the nests and checking their eggs' temperature, although it might be that none of the eggs are fertile.
Australia's Environment Protection and Biodiversity Conservation Act 1999 lists D. coriacea as vulnerable, while Queensland's Nature Conservation Act 1992 lists it as endangered. | Leatherback sea turtle | Wikipedia | 489 | 322578 | https://en.wikipedia.org/wiki/Leatherback%20sea%20turtle | Biology and health sciences | Turtles | Animals |
Agamidae is a family containing 64 genera, 582 species of iguanian lizards indigenous to Africa, Asia, Australia, and a few in Southern Europe. Many species are commonly called dragons or dragon lizards.
Overview
Phylogenetically, they may be sister to the Iguanidae, and have a similar appearance. Agamids usually have well-developed, strong legs. Their tails cannot be shed and regenerated like those of geckos (and several other families such as skinks), though a certain amount of regeneration is observed in some. Many agamid species are capable of limited change of their colours to regulate their body temperature. In some species, males are more brightly coloured than females, and colours play a part in signaling and reproductive behaviours. Although agamids generally inhabit warm environments, ranging from hot deserts to tropical rainforests, at least one species, the mountain dragon, is found in cooler regions. They are particularly diverse in Australia.
This group of lizards includes some more popularly known, such as the domesticated bearded dragon, Chinese water dragon, and Uromastyx species.
One of the key distinguishing features of the agamids is their teeth, which are borne on the outer rim of their mouths (acrodonts), rather than on the inner side of their jaws (pleurodonts). This feature is shared with the chameleons and the tuatara, but is otherwise unusual among lizards. Agamid lizards are generally diurnal, with good vision, and include a number of arboreal species, in addition to ground- and rock-dwellers. Most need to bask in the sun to maintain elevated body temperatures, meaning they are heliothermic. They generally feed on insects and other arthropods (such as spiders), although for some larger species, their diet may include small reptiles or mammals, nestling birds, and flowers or other vegetable matter. | Agamidae | Wikipedia | 393 | 322604 | https://en.wikipedia.org/wiki/Agamidae | Biology and health sciences | Iguania | Animals |
Reproduction
The great majority of agamid species are oviparous. The eggs are mostly found in damp soil or rotting logs to retain enough moisture during the incubation period. The clutch size varies from four to 10 eggs for most species, and incubation period lasts around 6–8 weeks. Specifically in the Leiolepidinae subfamily of agamids, all species use a burrowing system that reaches moist soil, where eggs are deposited in late spring/early summer or at the beginning of the dry season. The Leiolepidinae burrow system is also used for daily or seasonal retreats, as it allows them to regulate their body temperature or act as a refuge from predators.
Systematics and distribution
Very few studies of Agamidae have been conducted. The first comprehensive assessment was by Moody (1980) followed by a more inclusive assessment by Frost and Etheridge (1989). Subsequent studies were based on mitochondrial DNA loci by Macey et al. (2000) and Honda et al. (2000) and also by sampling across the Agamidae by Joger (1991). Few other studies focused on clades within the family, and Agamidae have not been as well investigated as Iguanidae.
The agamids show a curious distribution. They are found over much of the Old World, including continental Africa, Australia, southern Asia, and sparsely in warmer regions of Europe. They are absent from Madagascar and the New World. The distribution is the opposite of that of the iguanids, which are found in just these areas, but absent in areas where agamids are found. A similar faunal divide is found in between the boas and pythons.
Further classification
Among Agamidae, six subfamilies are generally recognized:
Agaminae (Africa, Europe and south Asia)
Amphibolurinae (Australia and New Guinea, one species in Southeast Asia)
Draconinae (South and Southeast Asia)
Hydrosaurinae (Hydrosaurus, Papua New Guinea, the Philippines, and Indonesia)
Leiolepidinae (Leiolepis, Southeast Asia)
Uromastycinae (Saara and Uromastyx, Africa and South Asia)
These can be further split into 64 genera, as follows: | Agamidae | Wikipedia | 459 | 322604 | https://en.wikipedia.org/wiki/Agamidae | Biology and health sciences | Iguania | Animals |
Acanthocercus (15 species)
Acanthosaura (20 species)
Agama (47 species)
Agasthyagama (2 species)
Amphibolurus (4 species)
Aphaniotis (3 species)
Bronchocela (15 species)
Bufoniceps (1 species)
Calotes (29 species)
Ceratophora (6 species)
Chelosania (1 species)
Chlamydosaurus (1 species)
Complicitus (1 species)
Cophotis (2 species)
Coryphophylax (2 species)
Cristidorsa (2 species)
Cryptagama (1 species)
Ctenophorus (38 species)
Dendragama (4 species)
Diploderma (47 species)
Diporiphora (28 species)
Draco (41 species)
Gonocephalus (17 species)
Gowidon (1 species)
Harpesaurus (6 species)
Hydrosaurus (5 species)
Hypsicalotes (1 species)
Hypsilurus (18 species)
Intellagama (1 species)
Japalura (8 species)
Laodracon (1 species)
Laudakia (13 species)
Leiolepis (10 species)
Lophocalotes (2 species)
Lophognathus (2 species)
Lophosaurus (3 species)
Lyriocephalus (1 species)
Malayodracon (1 species)
Mantheyus (1 species)
Microauris (1 species)
Moloch (1 species)
Monilesaurus (4 species)
Otocryptis (2 species)
Paralaudakia (8 species)
Pelturagonia (5 species)
Phoxophrys (1 species)
Phrynocephalus (36 species)
Physignathus (1 species)
Pogona (6 species)
Psammophilus (2 species)
Pseudocalotes (23 species)
Pseudocophotis (2 species)
Pseudotrapelus (6 species)
Ptyctolaemus (3 species)
Rankinia (1 species)
Saara (3 species)
Salea (2 species)
Sarada (3 species)
Sitana (15 species)
Trapelus (13 species)
Tropicagama (1 species)
Tympanocryptis (23 species)
Uromastyx (15 species)
Xenagama (4 species) | Agamidae | Wikipedia | 503 | 322604 | https://en.wikipedia.org/wiki/Agamidae | Biology and health sciences | Iguania | Animals |
Evolutionary history
The oldest known unambiguous agamid is Protodraco from the mid-Cretaceous (early Cenomanian) aged Burmese amber of Myanmar, dating to around 99 million years ago. It is similar to primitive living Southeast Asian agamids. Gueragama from the Late Cretaceous of Brazil may also be an agamid. Jeddaherdan, a supposed agamid from the Late Cretaceous of Morocco, was later shown to be actually a young subfossil of the living genus Uromastyx.
Predator responses
Body temperature helps determine the physiological state of agamids and affects their predator responses. A positive correlation is seen between a flight response (running speed) and body temperature of various agamid species. At higher body temperatures, these lizards tend to flee quickly from predators, whereas at lower temperatures, they tend to have a reduced running speed and show an increased fight response, where they are more likely to be aggressive and attack predators.
Certain physical features of some lizards of these species, such as frilled-neck lizards, play a role in their defensive responses, as well. During the mating season, males tend to display more of their frill, and give fight responses more often. Both males and females display their frills when they are threatened by predators, and during social interactions. | Agamidae | Wikipedia | 271 | 322604 | https://en.wikipedia.org/wiki/Agamidae | Biology and health sciences | Iguania | Animals |
Basiliscus is a genus of large corytophanid lizards, commonly known as basilisks, which are endemic to southern Mexico, Central America, and northern South America. The genus contains four species, which are commonly known as the Jesus Christ lizard, or simply the Jesus lizard, due to their ability to run across water for significant distances before sinking due to the large surface area of their feet.
Taxonomy and etymology
Both the generic name, Basiliscus, and the common name, "basilisk", derive from the Greek basilískos (βασιλίσκος) meaning "little king". The specific epithet, vittatus, which is Latin for "striped", was given in Carl Linnæus' 10th edition of Systema Naturæ.
Description
Basilisks on average measure in total length (including tail). Their growth is perpetual, fast when they are young and nonlinear for mature basilisks. Their skin is shed in pieces.
Basilisks are oviparous and lay 8–18 eggs.
Running on water
Basilisks sometimes run bipedally. Basilisks have the ability to "run" on water, and because of this, they have been dubbed the "Jesus Christ lizard" in reference to the biblical passage of Jesus walking on water. On water, basilisks can run at a velocity of per second for approximately before sinking on all fours and swimming. Flaps between their toes help support basilisks, creating a larger surface and pockets of air, giving them the ability to run across water.
A similar behavior, running bipedally across water, is known from the sailfin lizards and a few species of anole lizards.
Other defense mechanisms
Basilisks can burrow into sand to hide from predators; a ring of muscles around both nostrils prevents sand from entering the nose.
Habitat and geographic range
Basilisks are abundant in the tropical rain forests of Central and South America, from southern Mexico to Ecuador and Venezuela.
Invasive species
The species Basiliscus vittatus (brown basilisk) has been introduced to Florida. It has adapted to the colder winters by burrowing into leaf litter for warmth. Current reports sight the brown basilisk as far north as Fort Pierce, on the state's East Coast, where small groups have crept up the North Fork of the Saint Lucie River. Mainly it has been seen in Boca Raton and other cities in Palm Beach County. as seen in this photo taken in West Palm Beach, Florida. | Basiliscus (lizard) | Wikipedia | 509 | 322628 | https://en.wikipedia.org/wiki/Basiliscus%20%28lizard%29 | Biology and health sciences | Iguania | Animals |
Classification
Genus Basiliscus has four extant species: | Basiliscus (lizard) | Wikipedia | 10 | 322628 | https://en.wikipedia.org/wiki/Basiliscus%20%28lizard%29 | Biology and health sciences | Iguania | Animals |
Dactyloidae are a family of lizards commonly known as anoles () and native to warmer parts of the Americas, ranging from southeastern United States to Paraguay. Instead of treating it as a family, some authorities prefer to treat it as a subfamily, Dactyloinae, of the family Iguanidae. In the past they were included in the family Polychrotidae together with Polychrus (bush anoles), but the latter genus is not closely related to the true anoles.
Anoles are small to fairly large lizards, typically green or brownish, but their color varies depending on species and many can also change it. In most species at least the male has a dewlap, an often brightly colored flap of skin that extends from the throat and is used in displays. Anoles share several characteristics with geckos, including details of the foot structure (for climbing) and the ability to voluntarily break off the tail (to escape predators), but they are only very distantly related, anoles being part of Iguania.
Anoles are active during the day and feed mostly on small animals such as insects, but some will also take fruits, flowers, and nectar. Almost all species are fiercely territorial. After mating, the female lays an egg (occasionally two); in many species she may do so every few days or weeks. The egg is typically placed on the ground, but in some species it is placed at higher levels.
Anoles are widely studied in fields such as ecology, behavior, and evolution, and some species are commonly kept in captivity as pets. Anoles can function as a biological pest control by eating insects that may harm humans or plants, but represent a serious risk to small native animals and ecosystems if introduced to regions outside their home range.
Distribution and habitat
Anoles are a very diverse and plentiful group of lizards. They are native to tropical and subtropical South America, Central America, Mexico, the offshore East Pacific Cocos, Gorgona and Malpelo Islands, the West Indies and southeastern United States. | Dactyloidae | Wikipedia | 419 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
A particularly high species richness exists in Cuba (more than 60 species), Hispaniola (more than 55), Mexico (more than 50), Central America, Colombia (more than 75), and Ecuador (at least 40). Fewer live in eastern and central South America (for example, less than 20 species are known from huge Brazil), Contiguous United States (1 native species), and the Lesser Antilles (about 25 species in total, with 1–2 species on each island). However, the Lesser Antilles are relatively rich compared to their very small land area and their species are all highly localized endemics, each only found on one or a few diminutive islands. In South America, the diversity is considerably higher west of the Andes (Tumbes-Chocó-Magdalena region) than east (Amazon basin), as well illustrated in Ecuador where about of the anole species live in the former region and in the latter.
The only species native to the contiguous United States is the Carolina (or green) anole, which ranges as far west as central Texas, and north to Oklahoma, Tennessee and Virginia. Its northern limit is likely related to cold winter temperatures. Several anole species have been introduced to the contiguous US, mostly Florida, but also other Gulf Coast states and California. The most prevalent of these introductions is the brown anole. In contrast to the contiguous United States, Puerto Rico and the Virgin Islands are home to 16 native species, all endemic. | Dactyloidae | Wikipedia | 302 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Anoles inhabit a wide range of habitats, from highlands (up to at least above sea level) to the coast, and rainforest to desert scrub. A few live in limestone karst habitats and at least two of these, the Cuban cave anole and Mexican cave anole, will enter caves, sometimes occurring as much as from the entrance. Some species live close to humans and may use fences or walls of building as perches, even inhabiting gardens or trees along roads in large cities like Miami. Most anoles are arboreal or semi-arboreal, but there are also terrestrial and semiaquatic species. They are often, especially in the Caribbean, grouped into six ecomorphs—crown giant, trunk crown, trunk, trunk ground, twig, and grass bush—that inhabit specific niches. Other less widely used groups are ground, ground bush, twig giant, saxicolous, and riparian (alternatively semi-aquatic). However, the species within each ecomorph group are not entirely alike and there are variations in the details of their niches, including both widespread generalists and more restricted specialists. The niche differentiation allows several anoles to inhabit the same locality, with up to 15 species at a single site.
Appearance and behavior
Anoles vary in size. Males generally reach a larger size than females, but in a few species it is the other way around. Adults of most anoles are between in snout-to-vent length, and between in total length, including the tail. In the smallest, the five-striped grass anole, the snout-to-vent length is about in females and males respectively, but it is a relatively long-tailed species. There are several large species that are more than in snout-to-vent length. Males of the largest, the knight anole, reach up to about in snout-to-vent length, in total length, and in weight. There are both robust and gracile species, and the head shape varies from relatively broad to elongate. | Dactyloidae | Wikipedia | 417 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
The tail of anoles varies, but mostly it is longer than the snout-to-vent length. Depending on exact species it can range from slightly shorter to about three times the snout-to-vent. The Caribbean twig ecomorph anoles, proboscis anole and "Phenacosaurus" anoles have a prehensile tail. Semi-aquatic anoles tend to have relatively tall, vertically flattened tails that aid in swimming, and their skin has certain microstructures that make it hydrophobic, resulting in a thin film of air on the skin surface when submerged and preventing water from staying on when exiting the water.
Underneath an anole's toes are pads that have several to a dozen flaps of skin (adhesive lamellae) going horizontally and covered in microscopic hairlike protrusions (setae) that allow them to cling to many different surfaces, similar to but not quite as efficient as a gecko. Despite this similarity, they are very distantly related and the adaptions are the result of convergent evolution in the two groups. The extent of these structures and clinging ability varies, being more developed in anole species that live high in the tree canopy than ones living at lower levels. In one extreme are anoles that easily can run up windows. In the opposite end of the spectrum is the bulky anole of arid coastal Venezuela and adjacent Colombia, which is the only species completely lacking the specialized toe pad structures. The relative length of the limbs vary, mainly between different species, but to some extent also between different populations of a single species. This depends on things like the preferred perch size and whether there are ground-living predators in a habitat.
Despite having relatively small eyes, their primary sense is sight, which is excellent and in color. Their pupils are round or nearly round. The Guantanamo anole and Cuban cave anole have a transparent "window" in their lower eyelid, allowing them to see even with closed eyes, but why they have this adaption is unclear. Anoles have a good directional hearing, which is able to detect frequencies between 1000 and 7000 Hz and relatively low intensity sounds like the click of a camera.
Anoles are diurnal—active during the daytime—but can also be active during bright moonlit nights and may forage near artificial lights. Many species frequently bask in the sun to increase their temperature, but others are shade-living and do not.
Colors | Dactyloidae | Wikipedia | 500 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Most anoles are brownish or green, but there are extensive variations depending on the exact species. The majority can change their color depending on things like emotions (for example, aggression or stress), activity level, levels of light and as a social signal (for example, displaying dominance), but evidence showing that they do it in response to the color of the background (camouflage) is lacking. Whether they do it in response to temperature (thermoregulation) is less clear, with studies supporting it and contradicting it. The extent and variations of this color changing ability differ widely throughout the individual species. For example, the Carolina (or green) anole can change its color from a bright, leafy green to a dull brown color, while the brown anole can only change its shade, ranging from pale gray-brown to very dark brown. Even the distinct green-to-brown change in the Carolina anole can happen in only a few minutes. The colors are the result of their skin pigment cells, the chromatophores, of which they have three main types, but the change occurs only in the melanophores. When triggered by melanophore-stimulating hormone and other hormones, the melanosomes of the melanophores partially cover the other skin pigment cells, giving the anole a darker or browner color. In most cases stress results in a darker/browner color, but in the aquatic anole, a species that is dark brown with a barred pattern and light brown stripes on the sides of its body and head, stress results in paler brown upper parts and the stripes turn pale blue-green.
Their colors during the night when sleeping often differ distinctly from their colors during the day where awake. Among these are some species that otherwise do not drastically change their colors, including certain anoles that generally are brown during the day changing to greenish or whitish when sleeping at night, and certain anoles that generally are green during the day changing to brown when sleeping at night. | Dactyloidae | Wikipedia | 410 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Disregarding color change, minor individual variations in the basic color and pattern, mostly related to sex or age, are common. In some anole species this variation is more pronounced and not only related to sex and age. An example of this is the basic color of the Cayman blue-throated anole, which varies geographically, roughly matching the main habitat at a location. In others it occurs at the same location. This includes the extensive individual variations in the Guadeloupean anole, which however also shows some geographic variations, but possibly not consistent enough (due in part to clines) to make the typically recognized subspecies valid. In the Puerto Rican giant anole, a species only able to perform minor color changes (essentially lightness/darkness), juveniles are gray-brown and adults typically green, but an uncommon morph maintains a gray-brown color into adulthood. Similarly, rare morphs of the usually green Carolina anole lack certain pigment cells, giving them a mainly turquoise-blue or yellow color.
Dewlap
Most—but not all—anole species have dewlaps, made of erectile cartilage (modified from the hyoid) and covered in skin, that extend from their throat areas. When not in use and closed it lies inconspicuously along the throat and chest. The size, shape, color and pattern of the dewlap vary extensively depending on species, and often it differs between the sexes, being smaller (in some absent) or less colorful in females. In a few species, including the Carolina, bark, Cochran's gianthead and slender anoles, it varies geographically in color depending on subspecies or morph. Very locally, distinct morphs of a single species that differ in dewlap colors (not just differences between sexes) may occur together. In addition to colors that are visible to humans, dewlaps can have ultraviolet reflectance, which is visible to anoles. The striped anole is the only species where it is asymmetrically colored, being brighter on one side than the other. In some species even juveniles have a dewlap. The West Cuban and Cuban stream anoles are the only where both sexes lack a dewlap, but it is reduced and diminutive in about a dozen other species. | Dactyloidae | Wikipedia | 467 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
The dewlap serves as a signal for attracting partners, territoriality, deterring predators and communicating condition. When several anoles live together the species almost always differ in their dewlap, indicating that it plays a role in species recognition. Studies however reveal a more complex pattern: The bark anole and short nosed anole species complex (which includes the Webster's and Cochran's gianthead anoles) are closely related and both vary in their dewlap color. In places where their ranges overlap their dewlaps often differ and there is little hybridization, but in some locations their dewlaps are alike. Where alike there can be higher levels of hybridization (indicating that they are more likely to confuse each other) or levels can be as low as regions where they differ (indicating that something else allows them to separate each other). Another example is the red-fanned stout and large-headed anoles, which are sister species that overlap in range and are very similar except for their dewlap color. They are highly aggressive to individuals of their own species, but not the other. When one species has its dewlap color modified to resemble the other, only a relatively minor or no increase in aggression occurs, indicating that they still can separate each other.
Several other Iguania genera, Draco, Otocryptis, Polychrus, Sarada and Sitana, have evolved relatively large, movable dewlaps independently of the anoles.
Sexual dimorphism | Dactyloidae | Wikipedia | 307 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
In some anoles the sexes are very similar and difficult to separated under normal viewing conditions, but most species exhibit clear sexual dimorphism, which allows one to fairly easily discern between adult males and females. In a few species the female is slightly larger than the male, but in others the sexes are about the same size. However, in most the males are larger, in some more than three times the mass of females. This size difference can result in differences in the microhabitat (for example, males using larger branches than females) and feeding (males on average eating large prey) between the sexes of a single species. Males of some species have proportionally far longer heads than females, but in others it is nearly alike. The crest along the nape, back and/or tail is larger in the males. In species with tall crests this difference can be obvious, but in small-crested species it is often inconspicuous and easily overlooked, especially when not raised. The dewlap is often larger in males; in some species only the male has a dewlap. In a few there are differences in the shape of the nose, but this is only known to be prominent in the proboscis and leaf-nosed anoles, which both have long-nosed males and more normal looking females (it is likely that something similar can be seen in smooth anole, but the female of that species is still unknown). A less obvious difference between anole sexes is the enlarged post-cloacal scales in males.
The males of many species are overall more brightly colored, while females are duller, more cryptic, and sometimes their upperparts have striped or lined patterns that serve to break up the outline of the anole. In general, the juvenile colors and pattern resemble those of the adult female. The dewlap tends to be more colorful in males, with clear differences being common among anoles of the mainland of the Americas and comparatively rarer in the Caribbean species.
Territoriality and breeding | Dactyloidae | Wikipedia | 410 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Almost all anole species are highly territorial, at least the males, but a few exceptions do exist, including the rock-living Agassiz's and Taylor's anoles where males do not defend a territory, and the grass anole where dominant males accept subordinant non-territorial males within their territory. Territorial anoles will fan their dewlap, bob their head, perform "push-ups", raise their crest and do a wide range of other behaviors to scare away potential competitors. If this does not scare off the intruder, a fight proceeds in which the two anoles attempt to bite each other. During fights some species of anoles are known to vocalize. In addition to the behaviors indicating dominance, anoles may move their head up and down in a head-nod display (not to be confused with the head-bob display where entire frontal part of body is moved through "push-ups"), which is a submissive sign. Females maintain a feeding territory. Males maintain a larger breeding territory, which overlaps with the feeding territory of one or several females. The home range is generally larger in males than in females, and larger in large anole species than in smaller. In a very small species like the Bahoruco long-snouted anole the home range can be as little is about and in a female and male, compared to a large species like the knight anole where they average about and . If removed from its territory an anole will usually be able to find its way back home in a relatively short time, but exactly how they do this is unclear. Generally being highly solitary animals, anoles will only infrequently congregate, but in colder regions individuals may rest adjacent to each other in groups during the winter.
In addition to differences in the appearance of the dewlap, the frequency of the dewlap opening/closing and the frequency and amplitude of the head bobbing differ between species, allowing them to separate each other. Territoriality is typically aimed at other individuals of the same species, but in a few cases it is also directed towards other anoles, as can be seen between the crested and Cook's anoles. Unlike most anoles with widely overlapping ranges, these two inhabit very similar niches and directly compete for resources. | Dactyloidae | Wikipedia | 472 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
The breeding period varies. In species or populations living in highly seasonal regions it is generally relatively short, typically during the wet season. It is prolonged, often even year-round, in species or populations living in regions with less distinct seasons. In some species where it is year-round the egg production is however higher during the rainy season than the dry season, and in many where it is prolonged but not year-round, it begins in the spring and ends in the fall. Males attract and court females by performing a range of behaviors, often mirroring those used to scare away competitors, including extending their dewlap and bobbing their heads. During mating the male inserts one of his hemipenes into the female's cloaca, fertilizing the egg inside the oviduct. The female may mate with multiple males, but is also able to store sperm inside her body for fertilization of eggs several months after mating. A female anole produces an egg in each ovary, meaning that when one is maturing in one of her follicles the yolk of another is forming in the other. The white shell only forms when the egg has been fertilized and females will sometimes lay infertile, unshelled yellowish eggs known as "slugs". The female lays one (occasionally two) eggs per time, which typically is placed casually on the ground among leaf-litter, under debris, logs or rocks, or in a small hole. In some species it is placed at higher levels in a bromeliad, tree hole or rock crevice. A small number of species lay their eggs together, forming a communal nest. Among these is the unusual Cuban cave anole where as many as 25 eggs may be glued together in a small cavity on the side of a cave wall. A nest that contained eggs from the bay anole and the geckos Sphaerodactylus armasi and Tarentola crombiei represents the only known multi-species communal nest for an anole and the only known communal nest involving more than one family of lizard. Although typically only laying a single egg per time (clutch), females of many anole species can lay an egg every five days to four weeks. Some only have a single clutch per year, while other species may have as many as 20 on average. Depending on species, anole eggs hatch after about 30–70 days.
Feeding | Dactyloidae | Wikipedia | 495 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Anoles are opportunistic feeders, and may attempt to eat any attractive meal that is of the right size. They primarily feed on insects like flies, grasshoppers, crickets, caterpillars, moths, butterflies, beetles and ants, and arachnids like spiders. Several species will also eat small vertebrates such as mice, small birds (including nestlings), lizards (including other anole species and Cannibalism of their own) and frogs. The slow-moving Cuban false chameleon anoles ("Chamaeleolis") are specialized snail-eaters, and a few semi-aquatic species like the Cuban stream anole may catch prey in water such as shrimp and small fish. In some species the average prey-size varies with the individual anole's size, age and sex, with juvenile anoles eating the smallest prey, adult females taking intermediate-sized prey and adult males the largest prey. In other species there are no clear differences in the preferred prey size, regardless of an individual's size and sex.
Hunting is done by sight, and they generally show a strong preference for moving prey over non-moving. Many will chase down or sneak up to a potential prey item, while others are sit-and-wait predators that pounce on prey when it gets close to the anole. Anoles have numerous small, sharp and pointed teeth that allow them to efficiently grab their prey. They are heterodonts with each tooth in the frontal half of the jaw having a single tip (unicuspid) and each in the rear half having three tips (tricuspid); one in the middle and a smaller behind and in front of it. Unusually, the Cuban false chameleon anoles have enlarged and blunt, molar-like teeth in the rear part of their jaw, allowing them to crush the shells of their snail prey.
In addition to animal prey, many anole species will take plant material, notably fruits, flowers and nectar, and overall they are best described as omnivorous. Some fruit-eating species, like the knight anole, may function as seed dispersers. Anoles have been recorded drinking sweetened water from hummingbird feeders. Anoles are vulnerable to drying out and generally need access to water for drinking, like dew or rain on leaves, although some species are less susceptible to water loss than others and are able to live in relatively arid places.
Predator avoidance and deterrence | Dactyloidae | Wikipedia | 505 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
A wide range of animals will eat anoles, such as large spiders, centipedes, predatory katydids, snakes, large frogs, lizards, birds, monkeys, bats and carnivoran mammals. At least in part of their range, snakes may be the most significant predator of anoles. For example, the Caribbean Alsophis and Borikenophis racers, and the Mexican, Central American and South American Oxybelis vine snakes feed mostly on lizards like anoles. Some reptile-eating snakes have a specialized venom that has little effect on humans, but it rapidly kills an anole. On some Caribbean Islands anoles make up as much as 40–75% of the diet of American kestrels. Large anoles may eat smaller individuals of other anole species and cannibalism—eating smaller individuals of their own species—is also widespread. There is a documented case of a small anole being captured and killed by an outside potted Venus flytrap plant. | Dactyloidae | Wikipedia | 205 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Anoles mainly detect potential enemies by sight, but their hearing range also closely matches the typical vocal range of birds. If hearing a predatory bird, like a kestrel or hawk, they increase their vigilance. When hearing a non-predatory bird little or no change happens. Most anole species will try to escape from a predator by rapidly running or climbing away, but some will move to the opposite side of a tree trunk (facing away from the would-be attacker), jump to the ground from their perch, or freeze when disturbed, hoping the adversary does not spot it. Some anole species will show their fitness by displaying their dewlap when encountering a predator; the greater the endurance of the anole, the greater the display. Conversely, when suddenly forced to share their habitat with an efficient anole predator like the northern curly-tailed lizard (for example, if it is introduced to a place where formerly not present), the anoles may decrease the amplitude of their head bobbing, making them less conspicuous, and may become slower to emerge from hiding (less willing to take a risk) after having been scared by a predator. Slow-moving anoles, like the twig ecomorphs of the Caribbean and many Dactyloa species of mainland Central and South America, are generally cryptically colored and often coordinate their movements with the wind, resembling the surrounding vegetation. A few semi-aquatic species will attempt to escape from predators by diving into water or running bipedally across it, similar to basilisks. However, the anoles lack the specialized toe fringes that helps basilisks when doing this.
Anole tails often have the ability to break off at special segments, which is known as autotomy. The tail continues to wriggle for a period after detaching, attracting the attention of the predator and commonly allowing the anole to escape. The tail is regenerated, but it takes more than two months to complete this process. About two dozen anoles, including almost all members of the latifrons species group, all in the chamaeleonidae species group and the La Palma anole, do not have the ability to autotomize the tail. | Dactyloidae | Wikipedia | 452 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
If caught or cornered, anoles will bite in self-defense. This can be relatively effective against some predators. When fighting back and biting, sometimes for as much as 20 minutes, Puerto Rican crested anoles escape from more than of all attacks by Puerto Rican racer snakes. Some species of anoles will vocalize (typically growls, chirps or squeals) when caught.
Evolution
The evolution of anoles has been widely studied, and they have been described as a "textbook example of adaptive radiation and convergent evolution". Especially the widespread convergent evolution seen in anoles living in the Greater Antilles has attracted the attention of scientists, and resulted in comparisons with the Darwin's finches of the Galápagos Islands, lemurs of Madagascar and cichlid fish in the African Great Lakes.
Ecomorphs and origin | Dactyloidae | Wikipedia | 170 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
On each major Greater Antillean Island (Cuba, Hispaniola, Puerto Rico and Jamaica), there are anole species that have adapted to specific niches and are referred to as ecomorphs: crown giant, trunk crown, trunk, trunk ground, twig and grass bush (a few additional, less widely used ecomorphs also exist). However, even within the Greater Antilles there are differences depending on island size and the amount of available habitats. The largest, Cuba and Hispaniola, have all six primary ecomorphs, while the smaller Puerto Rico and Jamaica have five and four respectively. Species living in a specific niche on each island tend to resemble each other in both appearance and behavior. For example, the Escambray twig anole of Cuba closely resembles the Puerto Rican twig and Jamaican twig anoles, as well as several species of twig ecomorphs from Hispaniola. Despite this they are not closely related and have adapted to their specific niche independently of each other. At least four of the six primary ecomorphs are of ancient origin as they have been documented in amber fossils from Hispaniola that are about 15–20 million years old (the two missing ecomorphs are crown giant and grass bush). Otherwise there are few known fossils, but early phylogenetic and immunological studies indicate that anoles originated 40–66 million years ago, first inhabitant Central or South America, and then came to the Caribbean (initially likely Cuba or Hispaniola). A more recent phylogenetic study, published in 2012, indicated that anoles originated in South America and diverged from other reptiles far earlier, about 95 million years ago. While a South American origin has been generally accepted, the very high age has been controversial and other studies published in 2011–2014 arrived at a lower age, estimating that anoles diverged from other reptiles 23–75, 53–72 or 81–83 million years ago, while a comprehensive study from 2017 estimated about 46–65 million years ago. This indicates that early anoles arrived on the Greater Antillean Islands in the Caribbean from the mainland of the Americas via rafting rather than overland via ancient (now submerged) land bridges. After arriving in the Caribbean they diversified into several new groups and one of these, the Norops lineage, later made its way back to mainland of the Americas.
Species and adaptability | Dactyloidae | Wikipedia | 492 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Species level evolution in anoles can be very slow. Martinique originally consisted of four tiny islands, which then merged into a single as a result of uplifting. Anoles lived on each of the tiny ancient islands and were isolated six to eight million years ago. Despite this long separation, they did not experience allopatric speciation, as mixed couples of the different Martinique anole populations can successfully reproduce and remain part of a single species. The Barbados anole is part of the same group, but Barbados remains a separate, isolated island. The genetic divergence between the different Martinique anole populations is similar to that between other Lesser Antillean anoles consistently recognized as separate species. Another Lesser Antillean species, the Guadeloupean anole, has several distinct populations that generally are recognized as subspecies. However, Guadeloupean anoles exhibit high individual variability and the populations widely intergrade, something that possibly has been enhanced by habitat changes by humans (allowing populations to easier come into contact with each other) and translocations of individuals. This indicates that the subspecies are invalid today. Genetic studies confirm that strong assortative mating between the different Guadeloupean anole populations does not exist, despite their distinct differences in appearance and them having separated about 650,000 years ago (confidence interval starting at 351,000 years). Hybridization between different anole species has rarely been documented. | Dactyloidae | Wikipedia | 287 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
In contrast to this, anoles can change rapidly in response to changes, which is an example of microevolution. They are one of the few known examples of "visible evolution" (i.e., where changes happen at a speed where they can be observed within a human lifetime), together with groups like stickleback fish, guppies and Peromyscus beach mice. In studies of brown anoles introduced to Florida it has been seen that they can become longer-legged in a single generation when living with the predatory, ground-living northern curly-tailed lizard (shorter-legged anoles are slower and easier to catch for the curly-tailed lizard). Over a longer period, however, their legs become shorter, which are better suited for perching on smaller branches higher off the ground, out of reach for the curly-tailed lizard. When brown anoles are introduced to small islands with low vegetation, their legs become shorter, better suited for rapidly moving among the shrunken shrubbery to catch insects and avoid predatory birds. Furthermore, in a study where brown anoles were introduced to seven small, anole-free Bahaman islands (anoles had disappeared because of Hurricane Frances), it was seen that—although all populations became shorter-legged within a few years—this was proportional to the leg-size of the founders. In other words: The few founder brown anoles introduced to one island were shorter-legged than the few introduced to another. Both populations became shorter-legged over time, but the first remained shorter-legged than the second. This is an example of the founder effect. Similarly, when brown anoles were introduced to Florida, the native Carolina (or green) anoles moved to higher perches and gained larger toe pads better suited for those perches. This adaptation occurred in just 20 generations. Anoles are also adapting to life with humans: Puerto Rican crested anoles living in cities have developed more adhesive lamellae on their toe pads than ones living in forests, reflecting the need for being able to climb very smooth surfaces like windows in the former habitat. In contrast to these fast changes, anole's adaptability to temperature changes has traditionally been considered relatively minor. Nevertheless, when Puerto Rican crested anoles in Florida (where introduced in the 1970s) were compared to the original, native population in Puerto Rico, it was discovered that the former had become adapted to colder temperatures, by about 3 °C (5.4 °F) | Dactyloidae | Wikipedia | 504 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
An even faster adaption was observed in Carolina anoles from Texas during the unusually cold winter of 2013–2014. Carolina anoles living in central Texas and further north were already adapted to relatively cold temperatures, but those of southern Texas were not. However, after the winter of 2013–2014, the cold tolerance of the southern Texan populations had increased by as much as 1.5 °C (2.7 °F) and their genomic profiles had changed to more closely resemble the more northerly living Carolina anoles | Dactyloidae | Wikipedia | 103 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Taxonomy
The name for this group of lizards originates from the Carib anoli. It was modified and used in French Creole, and then transferred to English via the genus name Anolis, coined by French zoologist François Marie Daudin in 1802.
Several family names have been used for the anoles in recent decades. Initially they were placed in Iguanidae. This family, then comprising several very different groups, was split into eight families in 1989, with anoles being part of Polychrotidae together with Polychrus (bush anoles). However, genetic studies have shown that Polychrus is closer to Hoplocercidae than the true anoles. The true anoles are closer to Corytophanidae (basilisks and relatives). The true anoles have therefore been transferred to their own family Dactyloidae, alternatively listed as subfamily Dactyloinae of family Iguanidae. The name Anolidae (Cope, 1864) has sometimes been used, but it is a junior synonym of Dactyloidae (Fitzinger, 1843).
More than 425 species of true anoles are known. New species are regularly described, including 12 in 2016 alone. Most of the recent discoveries have been from the mainland of the Americas, with fewer new anoles described from the comparatively better-known Caribbean Islands.
Genera | Dactyloidae | Wikipedia | 275 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Traditionally, all the true anoles were included in the genus Anolis and some continue to use this treatment, in which case it is the largest genus of reptile. An attempt of dividing this huge genus was already made in 1959–1960, when they were placed in two major groups, the so-called "alpha anoles" (comprising most anole subgroups) and "beta anoles" (equalling today's Norops). In the following decades other changes were recommended. This included a proposal to recognize four genera, Anolis, Chamaeleolis, Chamaelinorops and Phenacosaurus, in 1976. In 1986, it was proposed that eight should be recognized: the four from 1976, and Ctenonotus, Dactyloa, Norops and Semiurus (the last was later replaced by its senior synonym Xiphosurus). These changes were adopted by some and rejected by others, who continued placing all in Anolis. In 1998–1999, the first comprehensive molecular studies of the anoles were published, confirming the earlier suspicion that the so-called "beta anoles" are a monophyletic group, but the "alpha anoles" are not. Furthermore, the genus splits proposed in 1976 and 1986 caused problems, as the narrowly defined Anolis was not monophyletic. In 2004, a major review based on several types of data (both molecular and morphological) revealed several groups and partially confirmed the genetic results from 1998 to 1999. No major changes were proposed and all anoles were maintained in a broadly defined Anolis. Two recent studies, primarily genetic and published in 2012 and 2017, confirmed several of the groups found in earlier studies, but rejected others. They found that the anoles fall into eight primary clades. Some of these can be further subdivided: For example, Chamaeleolis (from Cuba) is one of two subclades within Xiphosurus and it is sometimes considered a valid genus (in which case Xiphosurus is restricted to Hispaniola, Puerto Rico and nearby smaller islands). In contrast, the earlier proposed genus Phenacosaurus (from the Andes and tepui highlands in northwestern South America) is now included in Dactyloa. The phylogenetic position of most species is clear, but in a few the available evidence is conflicting and/or labelled with considerable statistic uncertainty. | Dactyloidae | Wikipedia | 488 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
The relationship of Dactyloidae can be described with a cladogram. Whether the eight groups are best recognized as separate genera or only as clades within a single genus, Anolis, is disputed. A few families between Polychrotidae and Corytophanidae+Dactyloidae are not shown:
Relationship with humans
Anoles are model organisms often studied in fields such as ecology, behavior, physiology and evolution. The Carolina (or green) anole is the most-studied anole species, with the earliest dedicated studies being more than 100 years old, from the late 1800s. The Carolina anole was the first reptile where the entire genome was sequenced.
Anoles are harmless to humans, but if caught or cornered they will bite in self-defense. As typical of animals, the bite force is strongly correlated to the size of the anole. It causes little pain in the smaller anoles which usually do not break the skin. Large species have relatively strong jaws lined with small, sharp teeth, and their bite can be painful and result in a superficial wound, but it is still essentially harmless.
Some anole species are commonly kept in captivity as pets and especially the Carolina (or green) anole is often described as a good "beginner's reptile", but it too requires specialized care.
Anoles can function as a biological pest control by eating pest insects that may harm humans or plants. Anole abundances can be considerably higher in diversified agroecosystems (multiple different plant types) than high-intensity agroecosystems (typically only one or very few plant types, and regular use of agrochemicals), making the former particularly suitable for this type of pest control. However, because of their potential of becoming invasive species, releasing anoles outside their native range is strongly discouraged and often illegal, even if the species occurs elsewhere in a country (for example, it is illegal to release Carolina anoles in California, as its native range is in the Southeastern United States).
Conservation | Dactyloidae | Wikipedia | 419 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
The willingness of many anoles of living close to humans in heavily altered habitats have made them common. Some anoles can occur in very high densities, as illustrated by the Saint Vincent bush, Puerto Rican bush and spotted anoles where it has been estimated that there locally are almost 28,000 individuals per hectare (11,500 per acre) in the first species and at least 20,000–21,000 per hectare (8,000–8,500 per acre) in the last two. However, in most species the density is lower and in rare anoles it can be well below 100 individuals per hectare (40 per acre). Some are restricted to specific habitats such as primary rainforest, making them more vulnerable. In a review in 2017, it was found that more than 50 anole species had a known total range that covered or less around their type locality. , only 90 anoles, equalling less than one-quarter of the total number of recognized species, had been rated by the IUCN. Most of these are either least concern (not threatened) or data deficient (limited available data prevents an assessment), but 7 are considered vulnerable, 14 endangered and 1 critically endangered. Typical threats to these are habitat loss from both humans and extreme weather, or competition/predation by introduced species. For example, the Finca Ceres anole, a critically endangered species only known from a single unprotected location in Matanzas Province, Cuba, has suffered habitat loss both due to hurricanes and expanding agricultural land. A. amplisquamosus, a critically endangered species only known from highland forest in the Cusuco National Park region of Honduras, was common in the early 2000s, but by 2006 it had experienced a drastic decline and was only infrequently encountered. A clear explanation for this is lacking, although it may be related to habitat loss due to human development and agriculture. Similarly, A. landestoyi, which only was described in 2016 and has not been rated by the IUCN, is restricted to the Loma Charco Azul reserve in Hispaniola, but it is seriously threatened by continuing illegal habitat destruction by slash-and-burn agriculture, livestock grazing and production of wood charcoal. Certain highly localized species can be threatened by other anoles | Dactyloidae | Wikipedia | 464 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
The Cook's anole, found only in southwestern Puerto Rico and considered endangered by the Puerto Rico Department of Natural and Environmental Resources, faces habitat loss and fragmentation from human development, predation by introduced species (especially cats and rats) and direct competition from a more widespread native, the Puerto Rican crested anole. The Puerto Rican crested anole has also been introduced to Dominica where it locally is outcompeting the endemic Dominican anole, having already largely displaced the South Caribbean ecotype (traditionally subspecies Anolis o. oculatus), which possibly may require a captive breeding program to ensure its survival | Dactyloidae | Wikipedia | 123 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
Nevertheless, anoles overall do not appear to have experienced the widespread extinctions and extirpations prevalent among larger Caribbean reptiles. The Culebra Island giant anole is the only anole considered possibly extinct in recent history (other extinct anoles are prehistoric and only known from fossil remains that are millions of years old). Locals reported sighting of the Culebra Island giant anole as recent as the 1980s, but this likely involved misidentifications of young green iguanas. Others, at least the Morne Constant anole, do not grow as large today as they once did.
Species restricted to a specific habitat in relatively remote regions, infrequently visited by biologists looking for reptiles, are often virtually unknown and rarely recorded. In a review in 2017, it was found that 15 anole species only were known from their holotype. These may truly be rare and seriously threatened, as the proboscis anole, a species that only was known from a single specimen collected in 1953 until it was rediscovered in cloud forests of Ecuador in 2004. In others with few records, like the Neblina anole, this is not the case. It was initially known from six 1980s specimens from the remote Neblina highlands in Venezuela, but when the Brazilian part of these highlands were visited in 2017 it was discovered that the species was locally abundant. Some species are easily overlooked, even if common. For example, if searching for Orces' Andes anole during the night when asleep they can be fairly easy to find, but if visiting the same location during the day it can be very difficult to find any.
As introduced species
When introduced to regions outside their native range by humans, anoles may become invasive and represent a serious threat to small local animals. Such introductions may happen by mistake (for example, as "stowaways" on garden plants) or deliberately (as predators introduced to combat insects or release of pet anoles people no longer want). | Dactyloidae | Wikipedia | 402 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
In the contiguous United States, the Carolina anole has been introduced to California, the brown anole has been introduced to the Gulf Coast states and California, and the knight, Jamaican giant, bark, large-headed, Puerto Rican crested, Cuban green and Hispaniolan green anoles have been introduced to Florida. The Barbados and Morne Constant anoles have also been recorded in Florida, but do not appear to have become established. There are indications that the invasive brown anole is displacing the native Carolina anole in Florida and Texas by outcompeting it and eating its young. In the most disturbed habitats the Carolina anole may disappear entirely, but in less disturbed habitats where there is more cover (allowing young to avoid predation) it may remain fairly common, although it is forced to occur higher in trees where less visible to humans. Regardless, the Carolina anole is common and widespread overall, and it has itself been introduced to several regions outside its native range, including California, Kansas, Hawaii, Guam, Palau, the Bahamas, Cayman Islands, Anguilla, Belize, Tamaulipas in Mexico, and Japan's Okinawa and Ogasawara (Bonin) Islands. Although there are several records from Spain (both the mainland and the Canary Islands), none of these have become established. In Japan's Ogasawara Islands, the introduced Carolina anoles have caused declines in native lizards and diurnal insects, including the near-extinction of five endemic dragonfly species and the likely extinction of the Celastrina ogasawaraensis butterfly. This may be due to the ecological naïveté of the insects (before the introduction, there were no diurnal, highly arboreal lizards) and a very high anole density on these Japanese islands, as similar insect declines have not been reported from the Bahamas (which already had diurnal, arboreal lizards), or Guam, Saipan and Hawaii (where the anole density is lower). In addition to Florida, the Cuban green anole has been introduced to the Dominican Republic, São Paulo (Brazil) and Tenerife (Spain). In Florida and the Dominican Republic it competes with native anoles (Carolina anole and Hispaniolan green anole, respectively) and it is feared that something similar may happen in São Paulo. The same pattern can be seen in Dominica where the introduced Puerto Rican crested anole locally has displaced the endemic Dominican anole | Dactyloidae | Wikipedia | 501 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
The brown anole and Graham's anole have both been introduced to Bermuda where they threaten the very rare Bermuda rock lizard. This problem has not been reported for the Leach's and Barbados anoles, the other species introduced to Bermuda. In the Cayman Islands the endemic Cayman blue-throated anole has moved to higher perched in places where the introduced brown anole is present (similar to the Carolina anole in places where brown anoles are present). Outside the Americas, the brown anole has been introduced to Hawaii, Tenerife, Singapore and Taiwan, and it is able to change ant communities on the last of these islands | Dactyloidae | Wikipedia | 130 | 322654 | https://en.wikipedia.org/wiki/Dactyloidae | Biology and health sciences | Iguania | Animals |
The Iguanidae is a family of lizards composed of the iguanas, chuckwallas, and their prehistoric relatives, including the widespread green iguana.
Taxonomy
Iguanidae is thought to be the sister group to the collared lizards (family Crotaphytidae); the two groups likely diverged during the Late Cretaceous, as that is when Pristiguana and Pariguana, the two earliest fossil genera, are known from. The subfamily Iguaninae, which contains all modern genera, likely originated in the earliest Paleocene, at about 62 million years ago. The most basal extant genus, Dipsosaurus, diverged from the rest of Iguaninae during the late Eocene, about 38 million years ago, with Brachylophus following a few million years later at about 35 million years ago, presumably after its dispersal event to the Pacific. All other modern iguana genera formed in the Neogene period.
A phylogenetic tree of Iguaninae is shown here:
Description
Iguanas and iguana-type species are diverse in terms of size, appearance, and habitat. They typically flourish in tropical, warm climates, such as regions of South America and islands in the Caribbean and in the Pacific. Iguanas typically possess dorsal spines across their back, a dewlap on the neck, sharp claws, a long whip-like tail, and a stocky, squat build. Most iguanas are arboreal, living in trees, but some species tend to be more terrestrial, which means they prefer the ground. Iguanas are typically herbivores and their diets vary based on what plant life is available within their habitat. Iguanas across many species remain oviparious, and exhibit little to no parental care when their eggs hatch. They do, however, display nest-guarding behavior. Like all extant non-avian reptiles, they are poikilothermic, and also rely on regular periods of basking under the sun to thermoregulate. | Iguanidae | Wikipedia | 414 | 322664 | https://en.wikipedia.org/wiki/Iguanidae | Biology and health sciences | Iguania | Animals |
Distribution
All but one of modern iguana genera are native to the Americas, ranging from the deserts of the Southwestern United States through Mexico, Central America, and the Caribbean, to throughout South America down to northernmost Argentina. Some iguanas like I. iguana have spread from their native regions of Central and South America into many Pacific Islands, and even to Fiji, Japan, and Hawai'i, due to the exotic pet trade and illegal introductions into the ecosystems. Other iguanas, like the Galapagos pink iguana (C. marthae) are endemic only to specific regions on the Galapagos islands. The Grand Cayman blue iguana, C. lewisi, is endemic only to the Grand Cayman island, limited to a small wildlife reserve. The only non-American iguana species are the members of the genus Brachylophus and the extinct Lapitiguana, which are found on Fiji and formerly Tonga; their distribution is thought to be the result of the longest overwater dispersal event ever recorded for a vertebrate species, with them rafting over 8000 km across the Pacific from the Americas to the Fiji and Tonga.
Extant genera
Fossils
Cretaceous Pristiguana brasiliensis and Pariguana lancensis are later excluded from the family.
Classification
Several classification schemes have been used to define the structure of this family. The "historical" classification recognized all New World iguanians, plus Brachylophus and the Madagascar oplurines, as informal groups and not as formal subfamilies.
Frost and Etheridge (1989) formally recognized these informal groupings as families.
Macey et al. (1997), in their analysis of molecular data for iguanian lizards recovered a monophyletic Iguanidae and formally recognized the eight families proposed by Frost and Etheridge (1989) as subfamilies of Iguanidae.
Schulte et al. (2003) reanalyzed the morphological data of Frost and Etheridge in combination with molecular data for all major groups of Iguanidae and recovered a monophyletic Iguanidae, but the subfamilies Polychrotinae and Tropidurinae were not monophyletic.
Townsend et al. (2011), Wiens et al. (2012) and Pyron et al. (2013), in the most comprehensive phylogenies published to date, recognized most groups at family level, resulting in a narrower definition of Iguanidae. | Iguanidae | Wikipedia | 510 | 322664 | https://en.wikipedia.org/wiki/Iguanidae | Biology and health sciences | Iguania | Animals |
Historical classification
Family Iguanidae
Informal grouping anoloids: anoles, leiosaurs, Polychrus
Informal grouping basiliscines: casquehead lizards
Informal grouping crotaphytines: collared and leopard lizards
Informal grouping iguanines: marine, Fijian, Galapagos land, spinytail, rock, desert, green, and chuckwalla iguanas
Informal grouping morunasaurs: wood lizards, clubtails
Informal grouping oplurines: Madagascan iguanids
Informal grouping sceloporines: earless, spiny, tree, side-blotched and horned lizards
Informal grouping tropidurines: curly-tailed lizards, South American swifts, neotropical ground lizards
Frost et al. (1989) classification of iguanas
Family Corytophanidae
Family Crotaphytidae
Family Hoplocercidae
Family Iguanidae
Genus Amblyrhynchus – marine iguana
Genus Brachylophus – Fijian/Tongan iguanas
Genus Cachryx – spinytail iguanas
Genus Conolophus – Galápagos land iguanas
Genus Ctenosaura – spinytail iguanas
Genus Cyclura – West Indian rock iguanas
Genus Dipsosaurus – desert iguana
Genus Iguana – green and Lesser Antillean iguanas
Genus Sauromalus – chuckwallas
Genus Armandisaurus (extinct chuckwalla)
Genus Lapitiguana (extinct giant Fijian iguana)
Genus Pumilia (extinct Palm Springs iguana)
Genus Pristiguana (Cretaceous Brazilian iguana)
Family Opluridae
Family Phrynosomatidae
Family Polychridae
Family Tropiduridae | Iguanidae | Wikipedia | 357 | 322664 | https://en.wikipedia.org/wiki/Iguanidae | Biology and health sciences | Iguania | Animals |
Macey et al. (1997) classification of Iguanidae
Family Iguanidae
Subfamily Corytophaninae: casquehead lizards
Subfamily Crotaphytinae: collared and leopard lizards
Subfamily Hoplocercinae: wood lizards, clubtails
Subfamily Iguaninae: marine, Fijian, Galapagos land, spinytail, rock, desert, green, and chuckwalla iguanas
Subfamily Oplurinae: Madagascan iguanids
Subfamily Phrynosomatinae: earless, spiny, tree, side-blotched and horned lizards
Subfamily Polychrotinae: anoles, leiosaurs, Polychrus
Subfamily Tropidurinae: curly-tailed lizards, neotropical ground lizards, South American swifts
Schulte et al. (2003) classification of Iguanidae
Here families and subfamilies are proposed as clade names, but may be recognized under the traditional Linnean nomenclature.
Iguanidae
Corytophaninae: casquehead lizards
Crotaphytinae: collared and leopard lizards
Hoplocercinae: wood lizards, clubtails
Iguaninae: marine, Fijian, Galapagos land, spinytail, rock, desert, green, and chuckwalla iguanas
Oplurinae: Madagascan iguanids
Phrynosomatinae: earless, spiny, tree, side-blotched and horned lizards
Polychrotinae: anoles, leiosaurs, Polychrus
subclade of Polychrotinae Anolis: anoles
subclade of Polychrotinae Leiosaurini: leiosaurs
subclade of Leiosaurini Leiosaurae:
subclade of Leiosaurini Anisolepae:
subclade of Polychrotinae Polychrus
Tropidurinae: curly-tailed lizards, neotropical ground lizards, South American swifts
subclade of Tropidurinae Leiocephalus: curly-tailed lizards
subclade of Tropidurinae Liolaemini: South American swifts
subclade of Tropidurinae Tropidurini: neotropical ground lizards
Townsend et al. (2011), Wiens et al. (2012) and Pyron et al. (2013) classification of Iguanidae | Iguanidae | Wikipedia | 485 | 322664 | https://en.wikipedia.org/wiki/Iguanidae | Biology and health sciences | Iguania | Animals |
Family Corytophanidae
Family Crotaphytidae
Family Dactyloidae
Family Hoplocercidae
Family Iguanidae
Family Leiocephalidae
Family Leiosauridae
Family Liolaemidae
Family Opluridae
Family Phrynosomatidae
Family Polychrotidae
Family Tropiduridae | Iguanidae | Wikipedia | 64 | 322664 | https://en.wikipedia.org/wiki/Iguanidae | Biology and health sciences | Iguania | Animals |
Dibamidae or blind skinks is a family of lizards characterized by their elongated cylindrical body and an apparent lack of limbs. Female dibamids are entirely limbless and the males retain small flap-like hind limbs, which they use to grip their partner during mating. They have a rigidly fused skull, lack pterygoid teeth and external ears. Their eyes are greatly reduced, and covered with a scale.
They are small insectivorous lizards, with long, slender bodies, adapted for burrowing into the soil. They usually lay one egg with a hard, calcified shell, rather than the leathery shells typical of many other reptile groups.
The family Dibamidae has two genera, Dibamus with 23 species native to Southeast Asia, Indonesia, the Philippines, and western New Guinea and the monotypic Anelytropsis native to Mexico. Recent phylogenetic analyses place the dibamids as the sister clade to all the other lizards and snakes or classify them as sharing a common ancestor with the infraorder Gekkota, with Dibamidae and Gekkota forming the sister clade to all other squamates. Hoeckosaurus from the Oligocene of Mongolia represents the only fossil record of the group.
Characteristics
General appearance
Dibamids are burrower lizards characterized by their elongated bodies with blunt head and tail, and an apparent lack of limbs. Relatively small, blind skinks can reach a maximum length of 250 mm (9.8 in) from head to tail and the snout vent length (SVL) is variable between both genus Anelytropsis and Dibamus. In Anelytropsis, the tail is longer than in Dibamus and represents between 34 and the 38% of the snout vent length which can range from 77 to 180 mm (3 to 7 in). In Dibamus, the tail corresponds to 9 to 25% of the SVL that varies from 52 to 203 mm (2 to 8 in). | Dibamidae | Wikipedia | 405 | 322730 | https://en.wikipedia.org/wiki/Dibamidae | Biology and health sciences | Lizards and other Squamata | Animals |
Usually dibamids are dark colored, from brown to dark purple, with little to no variation along their body and frequently lack elaborate patterns. It is common to find a color gradation from the darker back towards a lighter ventral side. Scales are shiny and smooth and very similar and overlapping along with some variation in number and shape in the head and anal regions where males usually have additional scales to cover anal pores. Scale row counts varies between both genera; Anelytropsis has 19 to 25 rows whereas Dibamus has 18 to 33. In both groups osteoderms are absent.
General characteristics of the soft tissue includes a tongue that is covered in lamellae except in the tip, heavily modified ears without external openings or middle ear cavity or eustachian tubes, and highly reduced eyes that are covered by a scale and lack internal structure, particularly in Dibamus.
Limbs
Dibamids are lizards with highly reduced limbs but they are not completely limbless. Males and females have rudimentary poorly developed hind limbs containing a femur, tibia and fibula in males, and distal cartilage cap. These elements are more developed on Dibamus than in Anelytropsis. Female Dibamus lack the tibia and the fibula.
Skull
The skull is approximately 5 – 7 mm in length with reduced kinesis and a more rigid skull for burrowing. The combination of fossorial habits and small size, contributes to the development of a skull configuration that is frequently found in other groups of burrowers and miniaturized species. Among those characteristics are the closure of the supratemporal fenestra and the post-temporal fenestra, the relative large braincase, tubular or scroll-like palatines and modified jaw suspension mechanism with the quadrate articulating with the lateral wall of the braincase. | Dibamidae | Wikipedia | 378 | 322730 | https://en.wikipedia.org/wiki/Dibamidae | Biology and health sciences | Lizards and other Squamata | Animals |
Other characteristics of the skull of blind skinks include the absence of a parietal foramen, a well developed secondary palate formed by three different bones, the maxillae, vomers and palatines which are expanded ventromedially to form a scroll, and the lack of palatal teeth. Nasal and frontal bones are paired and contact each other in a W-shape suture with no overlap between the two bones, and several bones are lost (lacrimal, postorbital and jugal) or highly reduced (supratemporal and squamosal). The main cranial differences, besides sizes, between Anelytropsis and Dibamus is the presence of epipterygoid and postfrontal in the Central American genus.
The mandible of Dibamidae bears less than 10 teeth and is composed of only three bones, the dentary, the coronoid and the compound bone. A remnant of the splenial bone is only present in one species of Dibamus, Dibamus novaeguineae.
Classification
The family Dibamidae contains two genera, Anelytropsis and Dibamus, and the close relationship of the genera was based on two morphological characteristics that are unique to these groups, the secondary palate and the lamellae covering the tongue, and additional cranial characteristics that can be shared with other groups of lizards.
The anatomical characteristics that dibamids share with other squamates contributed to the formulation of different taxonomic hypothesis. Dibamids, and particularly Dibamus was considered to be part of geckos and precisely the family of legless geckos; snakes, considering the organization of the skull and jaw muscles; or was proposed to be closely related to a group of fossorial skinks with elongated bodies and reduced limbs.
Phylogeny
Relationships among Dibamidae | Dibamidae | Wikipedia | 390 | 322730 | https://en.wikipedia.org/wiki/Dibamidae | Biology and health sciences | Lizards and other Squamata | Animals |
The relationships within Dibamidae have only be assessed until recently in a phylogenetic analysis that included DNA sequences from seven nuclear genes and one mitochondrial gene for 8 species, seven species of Dibamus and the one species of Anelytropsis. This analysis shows that there are two major clades within Dibamidae, one that includes the one species form the genus Anelytropsis, Analytropsis papillous, and the species of Dibamus that are distributed along continental Southeast Asia (Dibamus greeri, Dibamus montanus, and Dibamus bourreti). The other clade includes species that are currently distributed in the peninsular Southeast Asia and Islands (Dibamus tiomanensis, Dibamus novaeguineae, Dibamus seramensis, and Dibamus celebensis). These clades diverged 72 million years ago. Anelytropsis diverged from all mainland Dibamus at approximately 69.2 million years ago.
Dibamidae and its relationship with Squamata
The relationship of Dibamidae with other Squamata (lizards and snakes) has a long history of phylogenetic studies in which the morphological characteristics are used to determine those relationships. Those analyses found close relationships between Dibamidae and all other lizards with elongated bodies, limb reduction and usually, a fossorial habit like amphisbaenians, snakes or fossorial skinks. In morphology based phylogenies, dibamids are sister taxa to amphisbaenians and the clade that includes amphisbaenians and Dibamidae is sister to all snakes. The close relationships of this groups are the result of convergent evolution among these groups since some of the morphological traits have evolved independently in different groups.
More recent phylogenies using DNA sequences of nuclear and mitochondrial genes include a large taxonomic sample of squamates and place dibamids as the sister group to all other lizards and snakes, or with Gekkota as the sister group to all other squamates. Phylogenetic evidence supports dibamids being the most basal squamates, being sister to all other lizards and snakes, and indicates that they diverged during the late Triassic, around 210 million years ago.
Biodiversity
There are two recognized genera within the family, Anelytropsis and Dibamus. According to The Reptile Database, Anelytropsis is monotypic and Dibamus includes 23 species:
Anelytropsis | Dibamidae | Wikipedia | 511 | 322730 | https://en.wikipedia.org/wiki/Dibamidae | Biology and health sciences | Lizards and other Squamata | Animals |
Anelytropsis papillosus
Dibamus
Dibamus alfredi
Dibamus bogadeki
Dibamus booliati
Dibamus bourreti
Dibamus celebensis
Dibamus dalaiensis
Dibamus deharvengi
Dibamus dezwaani
Dibamus floweri
Dibamus greeri
Dibamus ingeri
Dibamus kondaoensis
Dibamus leucurus
Dibamus montanus
Dibamus nicobaricum
Dibamus novaeguineae
Dibamus seramensis
Dibamus smithi
Dibamus somsaki
Dibamus taylori
Dibamus tebal
Dibamus tiomanensis
Dibamus vorisi
For additional details, see here
An extinct monotypic genus, Hoeckosaurus was recently proposed from the description of fossil material from the early Oligocene of the Valley of Lakes in Central Mongolia.
Hoeckosaurus mongoliensis sp. nov.
Biogeography
Dibamids have a disjunct distribution with one genus living in Northern Mexico, Anelytropsis, and the other one, Dibamus, living in South East Asia. Biogeographical studies suggest that the separation between Anelytropsis and Dibamus, specifically the clade with species that are distributed in continental South East Asia, occurred approximately 69 million years ago during the late Cretaceous and the migration from Asia to North America took place during the Late Paleocene or Eocene through Beringia.
Biology
Blind skinks are insectivorous and feed on arthropods and earthworms. Blind skinks are characterized by their fossorial or burrowing habits. They can dig their own burrows, use old burrows or other openings in the ground, or dwell under the leaf litter or logs.
Species of the genus Dibamus are frequently found in primary and secondary forests in a wide range of altitudinal variation (from the sea level to approximately 1300 meters above sea level). Anelytropsis is found in drier environments and is adapted to xeric conditions of different environments in northern Mexico.
Little is known about the reproduction of this group of lizards, but the inspection of female specimens from herpetological collections indicate that dibamids lays single egg with hardened shell, and eggs are laid frequently, at least in Dibamus.
Conservation
None of the species of Dibamidae are listed as endangered species in the Convention on International Trade in Endangered Species of Wild Fauna and Flora CITES. | Dibamidae | Wikipedia | 508 | 322730 | https://en.wikipedia.org/wiki/Dibamidae | Biology and health sciences | Lizards and other Squamata | Animals |
The International Union for Conservation of Nature (IUCN) include some of the species of the genus Dibamus and the single species of Anelytropsis in the red list of endangered species, most are in the category of least concern, and two species, Dibamus kondaoensis and Dibamus tiomanensis are listed as nearly threatened and endangered respectively. | Dibamidae | Wikipedia | 74 | 322730 | https://en.wikipedia.org/wiki/Dibamidae | Biology and health sciences | Lizards and other Squamata | Animals |
The Lacertidae are the family of the wall lizards, true lizards, or sometimes simply lacertas, which are native to Afro-Eurasia. It is a diverse family with at about 360 species in 39 genera. They represent the dominant group of reptiles found in Europe.
Habitat
The European and Mediterranean species of lacertids live mainly in forest and scrub habitats. Eremias and Ophisops species replace these in the grassland and desert habitats of Asia. African species usually live in rocky, arid areas. Holaspis species are among the few arboreal lacertids, and its two species, Holaspis guentheri and Holaspis laevis, are gliders (although apparently poor ones), using their broad tail and flattened body as an aerofoil.
Description
Lacertids are small to medium-sized lizards. Most species are less than 9cm long, excluding the tail. The largest living species, Gallotia stehlini, reaches 46cm, and some extinct forms were larger still. They are primarily insectivorous. An exception is Meroles anchietae, one of the few wall lizards that regularly eat seeds – an appropriate food for a lizard of the harsh Namib Desert.
Lacertids are remarkably similar in form, with slender bodies and long tails, but have highly varied patterns and colours, even within the same species. Their scales are large on the head, which often also has osteoderms, small and granular on the back, and rectangular on the underside. Most species are sexually dimorphic, with the males and females having different patterns.
At least eight species from the Caucasus are parthenogenetic, and three species give birth to live young, including the viviparous lizard, Zootoca vivipara.
Evolutionary history
Lacertids are suspected to have originated in Europe, due to their earliest fossils being found in the region, alongside those of their sister group, the extinct Eolacertidae. Fossils possibly attributable to lacertids are known from the Paleocene of France and Belgium. The oldest definitive lacertid is known from the early Eocene (Ypresian) in Mutigny, France in the Paris Basin. Lacertids dispersed into Asia by the early Oligocene. The timing of the colonisation of Africa is uncertain, ranging from the Eocene to the Miocene.
Classification
The classification into subfamilies and tribes below follows one presented by Arnold et al., 2007, based on their phylogenetic analysis. | Lacertidae | Wikipedia | 512 | 322739 | https://en.wikipedia.org/wiki/Lacertidae | Biology and health sciences | Lizards and other Squamata | Animals |
Family Lacertidae
Subfamily Gallotiinae
Genus Gallotia (8 species)
Genus Psammodromus (8 species)
Subfamily Lacertinae
Tribe Eremiadini
Genus Acanthodactylus (45 species)
Genus Adolfus (6 species)
Genus Australolacerta (1 species)
Genus Congolacerta (2 species)
Genus Eremias (42 species)
Genus Gastropholis (4 species)
Genus Heliobolus (6 species)
Genus Holaspis (2 species)
Genus Ichnotropis (6 species)
Genus Latastia (10 species)
Genus Meroles (8 species)
Genus Mesalina (20 species)
Genus Nucras (13 species)
Genus Ophisops (11 species)
Genus Pedioplanis (16 species)
Genus Philochortus (7 species)
Genus Poromera (1 species)
Genus Pseuderemias (7 species)
Genus Tropidosaura (4 species)
Tribe Lacertini
Genus Algyroides (4 species)
Genus Anatololacerta (4 species)
Genus Apathya (2 species)
Genus Archaeolacerta (1 species)
Genus Atlantolacerta (1 species)
Genus Dalmatolacerta (1 species)
Genus Darevskia (35 species)
Genus Dinarolacerta (2 species)
Genus Hellenolacerta (1 species)
Genus Iberolacerta (8 species)
Genus Iranolacerta (2 species)
Genus Lacerta (10 species)
Genus Omanosaura (2 species)
Genus Parvilacerta (2 species)
Genus Phoenicolacerta (4 species)
Genus Podarcis (26 species)
Genus Scelarcis (1 species)
Genus Takydromus (24 species)
Genus Teira (1 species)
Genus Timon (6 species)
Genus Vhembelacerta (1 species)
Genus Zootoca (2 species)
The latest extensive phylogenetic lacertid tree was made by Baeckens et al. in 2015.
Extinct genera | Lacertidae | Wikipedia | 417 | 322739 | https://en.wikipedia.org/wiki/Lacertidae | Biology and health sciences | Lizards and other Squamata | Animals |
†Succinilacerta Baltic amber, Eocene
†Plesiolacerta Europe, Eocene-Oligocene
†Dracaenosaurus France, Oligocene
†Maioricalacerta Mallorca, Pliocene
†Quercycerta France, Eocene
†Janosikia Germany, Miocene
†Escampcerta France, Eocene
†Mediolacerta France, Germany, Oligocene
†Pseudeumeces France, Germany, Spain, Oligocene-Miocene
†Amblyolacerta France, Czech Republic, Miocene
†Ligerosaurus France, Miocene
†Miolacerta Germany, Austria, Czech Republic, Oligocene-Miocene
†Edlartetia Augé and Rage 2000 Germany, France Austria, Miocene
†Escampcerta France, Eocene
†Cernaycerta? France, Paleocene (questioned by some authors)
†Dormaalisaurus France, Belgium, Spain, Eocene | Lacertidae | Wikipedia | 192 | 322739 | https://en.wikipedia.org/wiki/Lacertidae | Biology and health sciences | Lizards and other Squamata | Animals |
Teiidae is a family of Lacertoidean lizards native to the Americas. Members of this family are generally known as whiptails or racerunners; however, tegus also belong to this family. Teiidae is sister to the Gymnopthalmidae, and both families comprise the Teiioidea. The Teiidae includes several parthenogenic species – a mode of clonal reproduction. Presently, the Teiidae consists of approximately 150 species in eighteen genera.
Morphology and behavior
Teiids can be distinguished from other lizards by the following characteristics: large rectangular scales that form distinct transverse rows ventrally and generally small granular scales dorsally, head scales that are separate from the skull bones, and teeth that are solid at the base and "glued" to the jaw bones. Additionally, all teiids have a forked, snake-like tongue. They all possess well-developed limbs.
Teiids are all terrestrial (few are semi-aquatic) and diurnal, and are primarily carnivorous or insectivorous. Most teiids forage quite actively within their ideal temperature range, quickly skirting between cover objects. Some will include a small amount of plant matter in their diet. They are oviparous, and some species lay very large clutches.
Parthenogenesis
Several species of whiptail lizards are entirely female and no males are known. These all-female species reproduce by obligate parthenogenesis (obligate, because the lizards do not involve males and cannot reproduce sexually). Like all squamate obligate parthenogenetic lineages, parthenogenetic teiids are hybrids. Two or more species rarely hybridize and the offspring are thought to occasionally be capable of reproduction without sperm. The meiotic mechanism for bypassing fertilization is an ongoing area of research.
Primarily known from lab studies of parthenogenetic Aspidoscelis neomexicanus, simulated mating behavior can increase fertility. In this behavior known as pseudocopulation, one female assumes a male-like role and the other a female-like role. Individuals can switch roles throughout their life. The claim of pseudocopulation was initially met with hesitation by some researchers, and the behavior has not been observed in all parthenogenetic varieties. Since at least some all-female lineages exhibit pseudocopulation, these lizards can be considered to reproduce unisexually (in contrast to asexually). | Teiidae | Wikipedia | 502 | 322882 | https://en.wikipedia.org/wiki/Teiidae | Biology and health sciences | Lizards and other Squamata | Animals |
Fossil record
Teiids are known to have briefly occurred in Europe during the Late Eocene based on fragmentary fossil material non-diagnostic to the genus level found in the Quercy Phosphorites Formation of France dating to the MP 17 zone.
Taxonomy
The Teiidae contains approximately 150 species divided into two subfamilies and 18 genera. This assessment includes several recent changes: three resurrected genera, five newly described genera, and the large genus Cnemidophorus split into Aspidoscelis and Cnemidophorus. In some technical literature, the Teiidae are referred to as macroteiids (in opposition to the microteiids, which are members of a sister family Gymnopthalmidae). Parthenogenetic lineages are generally referred to as species, though the concept of a species is meant loosely. Other terms include array, clone, type, or morph.
Subfamily Teiinae:
Ameiva – junglerunners (14 species)
Ameivula – (11 species)
Aspidoscelis – North American whiptail lizards (46 species)
Aurivela – (2 species)
Cnemidophorus – South American whiptail lizards (19 species)
Contomastix – (6 species)
Dicrodon – desert tegus (3 species)
Glaucomastix – (5 species)
Holcosus – (18 species)
Kentropyx – (9 species)
Medopheos – (1 species)
Pholidoscelis – (20 species)
Teius – (3 species)
Subfamily Tupinambinae:
Callopistes – false monitors (4 species)
Crocodilurus – the crocodile tegu (1 species)
Dracaena – caiman lizards (3 species)
Salvator – (3 species)
Tupinambis – tegus (8 species) | Teiidae | Wikipedia | 384 | 322882 | https://en.wikipedia.org/wiki/Teiidae | Biology and health sciences | Lizards and other Squamata | Animals |
Cordylidae is a family of small- to medium-sized lizards that occur in southern and eastern Africa. They are commonly known as girdled lizards, spinytail lizards, or girdle-tail lizards.
Cordylidae is closely related to the family Gerrhosauridae, occurring in Africa and Madagascar. These two scientific families of lizards, known as Cordyliformes or Cordyloidea, are sometimes combined into a larger concept of Cordylidae. Recent molecular analyses confirm the clade made up of Cordylidae and Gerrhosauridae (Cordyloidea) and place it in a larger clade including Xantusiidae (Cordylomorpha Vidal & Hedges, 2009).
Description and behavior
Girdled lizards are diurnal and insectivorous. They are terrestrial, mostly inhabiting crevices in rocky terrain, although at least one species digs burrows and another lives under exfoliating bark on trees. They have flattened heads and bodies, and are distinguished by a heavy armour of osteoderms and large, rectangular, scales, arranged in regular rows around the body and tail. Many species have rings of spines on the tail, that aid in wedging the animal into sheltering crevices, and also in dissuading predators.
Most species have four limbs, but those in the genus Chamaesaura are almost entirely limbless, with only tiny spikes in place of the hind limbs. The family includes both egg-laying and ovoviviparous species.
Genera | Cordylidae | Wikipedia | 313 | 322886 | https://en.wikipedia.org/wiki/Cordylidae | Biology and health sciences | Lizards and other Squamata | Animals |
A sun dog (or sundog) or mock sun, also called a parhelion (plural parhelia) in atmospheric science, is an atmospheric optical phenomenon that consists of a bright spot to one or both sides of the Sun. Two sun dogs often flank the Sun within a 22° halo.
The sun dog is a member of the family of halos caused by the refraction of sunlight by ice crystals in the atmosphere. Sun dogs typically appear as a pair of subtly colored patches of light, around 22° to the left and right of the Sun, and at the same altitude above the horizon as the Sun. They can be seen anywhere in the world during any season, but are not always obvious or bright. Sun dogs are best seen and most conspicuous when the Sun is near the horizon.
Formation and characteristics
Sun dogs are commonly caused by the refraction and scattering of light from horizontally oriented plate-shaped hexagonal ice crystals either suspended in high and cold cirrus or cirrostratus clouds, or drifting in freezing moist air at low levels as diamond dust. The crystals act as prisms, bending the light rays passing through them with a minimum deflection of 22°. As the crystals gently float downwards with their large hexagonal faces almost horizontal, sunlight is refracted horizontally, and sun dogs are seen to the left and right of the Sun. Larger plates wobble more, and thus produce taller sun dogs.
Sun dogs are red-colored at the side nearest the Sun; farther out the colors grade through oranges to blue. The colors overlap considerably and are muted, never pure or saturated. The colors of the sun dog finally merge into the white of the parhelic circle (if the latter is visible).
The same plate-shaped ice crystals that cause sun dogs are also responsible for the colorful circumzenithal arc, meaning that these two types of halo tend to co-occur. The latter is often missed by viewers, since it is located more or less directly overhead. Another halo variety often seen together with sun dogs is the 22° halo, which forms a ring at roughly the same angular distance from the sun as the sun dogs, thus appearing to interconnect them. As the Sun rises higher, the rays passing through the plate crystals are increasingly skewed from the horizontal plane, causing their angle of deviation to increase and the sun dogs to move farther from the 22° halo, while staying at the same elevation. | Sun dog | Wikipedia | 501 | 323221 | https://en.wikipedia.org/wiki/Sun%20dog | Physical sciences | Atmospheric optics | Earth science |
It is possible to predict the forms of sun dogs as would be seen on other planets and moons. Mars might have sun dogs formed by both water-ice and CO2-ice. On the giant planets—Jupiter, Saturn, Uranus, and Neptune—other crystals form clouds of ammonia, methane, and other substances that can produce halos with four or more sun dogs.
A related phenomenon, the Crown flash is also known as a "leaping Sundog".
Terminology
A somewhat common misconception among the general public is to refer to any member of the ice halo family as a "sun dog" (especially the 22° halo, being one of the most common varieties). However, sun dogs represent just one of many different types of halos. For referring to the atmospheric phenomenon in general, the term (ice crystal) halo(s) is more appropriate.
Etymology
The exact etymology of sun dog largely remains a mystery. The Oxford English Dictionary says it is "of obscure origin".
In Abram Palmer's 1882 book Folk-etymology: A Dictionary of Verbal Corruptions Or Words Perverted in Form Or Meaning, by False Derivation Or Mistaken Analogy, sun-dogs are defined:
(Dog in English as a verb can mean "hunt, track, or follow", so Dog the true [sun] has meant track the true [sun] since the 1510s.)
Alternatively, Jonas Persson suggested that out of Norse mythology and archaic names — (sun dog), (sun dog), (sun wolf) — in the Scandinavian languages, constellations of two wolves hunting the Sun and the Moon, one after and one before, may be a possible origin for the term.
Parhelion (plural parhelia) comes from (, 'beside the sun'; from (, 'beside') and (, 'sun')).
In the Anglo-Cornish dialect of Cornwall, United Kingdom, sun dogs are known as weather dogs (described as "a short segment of a rainbow seen on the horizon, foreshowing foul weather"). It is also known as a lagas in the sky which comes from the Cornish language term for the sun dog meaning 'weather's eye' (, 'eye' and , 'weather/wind'). This is in turn related to the Anglo-Cornish term cock's eye for a halo round the Sun or the Moon, also a portent of bad weather.
History
Antiquity | Sun dog | Wikipedia | 497 | 323221 | https://en.wikipedia.org/wiki/Sun%20dog | Physical sciences | Atmospheric optics | Earth science |
Aristotle (Meteorology III.2, 372a14) notes that "two mock suns rose with the sun and followed it all through the day until sunset." He says that "mock suns" are always to the side, never above or below, most commonly at sunrise or sunset, more rarely in the middle of the day.
The poet Aratus (Phaenomena, lines 880–891) mentions parhelia as part of his catalogue of Weather Signs; according to him, they can indicate rain, wind, or an approaching storm.
Artemidorus in his Oneirocritica ('On the Interpretation of Dreams') included the mock suns amongst a list of celestial deities.
A passage in Cicero's On the Republic (54–51 BC) is one of many Roman authors who refer to sun dogs and similar phenomena:
Seneca makes an incidental reference to sun dogs in the first book of his Naturales Quaestiones.
The 2nd-century Roman writer and philosopher Apuleius in his Apologia says "What is the cause of the prismatic colours of the rainbow, or of the appearance in heaven of two rival images of the sun, with sundry other phenomena treated in a monumental volume by Archimedes of Syracuse."
Fulcher of Chartres, writing in Jerusalem in the early twelfth century, notes in his Historia Hierosolymitana (1127) that on February 23, 1106
Wars of the Roses
The prelude to the Battle of Mortimer's Cross in Herefordshire, England in 1461 is supposed to have involved the appearance of a halo display with three "suns". The Yorkist commander, later Edward IV of England, convinced his initially frightened troops that it represented the three sons of the Duke of York, and Edward's troops won a decisive victory. The event was dramatized by William Shakespeare in King Henry VI, Part 3, and by Sharon Kay Penman in The Sunne In Splendour.
Early modern era
Another early clear description of sun dogs is by Jacob Hutter, who wrote in his Brotherly Faithfulness: Epistles from a Time of Persecution: | Sun dog | Wikipedia | 439 | 323221 | https://en.wikipedia.org/wiki/Sun%20dog | Physical sciences | Atmospheric optics | Earth science |
The observation most likely occurred in Auspitz (Hustopeče), Moravia on 31 October 1533. The original was written in German and is from a letter originally sent in November 1533 from Auspitz in Moravia to the Adige Valley in South Tyrol. The Kuntz Maurer and Michel Schuster mentioned in the letter left Hutter on the Thursday after the feast day of Simon and Jude, which is 28 October. The Thursday after was 30 October. It is likely that the "two rainbows with their backs turned toward each other, almost touching" involved two further halo phenomena, possibly a circumzenithal arc (prone to co-occur with sun dogs) together with a partial 46° halo or supralateral arc.
While mostly known and often quoted for being the oldest color depiction of the city of Stockholm, Vädersolstavlan (Swedish; "The Sundog Painting", literally "The Weather Sun Painting") is arguably also one of the oldest known depictions of a halo display, including a pair of sun dogs. For two hours in the morning of 20 April 1535, the skies over the city were filled with white circles and arcs crossing the sky, while additional suns (i.e., sun dogs) appeared around the sun. The phenomenon quickly resulted in rumours of an omen of God's forthcoming revenge on King Gustav Vasa (1496–1560) for having introduced Protestantism during the 1520s and for being heavy-handed with his enemies allied with the Danish king.
Hoping to end speculations, the Chancellor Olaus Petri (1493–1552), a Lutheran scholar, ordered a painting to be produced documenting the event. When confronted with the painting, the King, however, interpreted it as a conspiracy — the real sun, of course, being himself —threatened by competing fake suns, one being Olaus Petri and the other the clergyman and scholar Laurentius Andreae (1470–1552). Both were thus accused of treachery, but eventually escaped capital punishment. The original painting is lost, but a copy from the 1630s survives and can still be seen in the church Storkyrkan in central Stockholm. | Sun dog | Wikipedia | 453 | 323221 | https://en.wikipedia.org/wiki/Sun%20dog | Physical sciences | Atmospheric optics | Earth science |
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