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94-626: The mole salamanders ( genus Ambystoma ) are a group of advanced salamanders endemic to North America. The group has become famous due to the presence of the axolotl ( A. mexicanum ), widely used in research due to its paedomorphosis , and the tiger salamander ( A. tigrinum, A. mavortium ) which is the official amphibian of many US states, and often sold as a pet. Terrestrial mole salamanders are identified by having wide, protruding eyes, prominent costal grooves , and thick arms. Most have vivid patterning on dark backgrounds, with marks ranging from deep blue spots to large yellow bars depending on

188-820: A caudal fin extending from behind the head to the vent. External gills are usually lost when salamander species mature into adulthood, although the axolotl maintains this feature. This is due to their neoteny evolution, where axolotls are much more aquatic than other salamander species. Their heads are wide, and their eyes are lidless. Their limbs are underdeveloped and possess long, thin digits. Males are identified by their swollen cloacae lined with papillae, while females are noticeable for their wider bodies full of eggs. Three pairs of external gill stalks (rami) originate behind their heads and are used to move oxygenated water. The external gill rami are lined with filaments (fimbriae) to increase surface area for gas exchange. Four-gill slits lined with gill rakers are hidden underneath

282-430: A damaged limb, as well as regenerating an additional one, ending up with an extra appendage that makes them attractive to pet owners as a novelty. In metamorphosed individuals, however, the ability to regenerate is greatly diminished. The axolotl is therefore used as a model for the development of limbs in vertebrates. There are three basic requirements for regeneration of the limb: the wound epithelium, nerve signaling, and

376-413: A different family that are not closely related to the axolotl but bear a superficial resemblance. A sexually mature adult axolotl, at age 18–27 months, ranges in length from 15 to 45 cm (6 to 18 in), although a size close to 23 cm (9 in) is most common and greater than 30 cm (12 in) is rare. Axolotls possess features typical of salamander larvae, including external gills and

470-423: A different genus. The genus name Ambystoma was given by Johann Jakob von Tschudi in 1839, and is traditionally translated as "cup-mouth",. Tschudi did not provide a derivation for the name, and many thought that he intended the name Amblystoma , "blunt-mouth." Occasionally, old specimens and documents use the name Amblystoma . Writing in 1907, Leonhard Stejneger offered a derivation of Ambystoma based on

564-638: A direct contributor to their regenerative abilities. Further research has been conducted to examine their heart as a model of human single ventricle and excessive trabeculation. Axolotls were also sold as food in Mexican markets and were a staple in the Aztec diet. Axolotls may be confused with the larval stage of the closely related tiger salamander ( A. tigrinum ), which are widespread in much of North America and occasionally become paedomorphic, or with mudpuppies ( Necturus spp.), fully aquatic salamanders from

658-629: A form of DNA repair that deals with double-strand breaks. Rhyacosiredon was previously considered a separate genus within the family Ambystomatidae. However, cladistic analysis of the mole salamanders found the existence of Rhyacosiredon makes Ambystoma paraphyletic , since the species are more closely related to some Ambystoma species than those species are to others in Ambystoma . The stream-type morphology of these salamanders (which includes larvae and neotenes with short gills and thicker gular folds ) may have led to their misclassification as

752-407: A genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of

846-787: A large number of possible nuclear biotypes (genome combinations) in the unisexuals. For example, an LJJ individual would be a triploid with one A. laterale genome and two A. jeffersonianum genomes, while an LTxJTi individual would be a tetraploid with genomes from four species. Because they have hybrid genomes, unisexual salamanders are a cryptic species with morphology similar to coexisting species. For example, LLJs look like blue-spotted salamanders and LJJs look like Jefferson salamanders. Silvery salamanders LJJ ( A. platineum ), Tremblay's salamanders LLJ ( A. tremblayi ), and Kelly's Island salamanders LTxTx and LTxTi ( A. nothagenes ) were initially described as species. Species names were later dropped for all unisexual salamanders because of

940-651: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

1034-671: A leucistic specimen) were shipped from Mexico City to the Jardin des Plantes in Paris in 1863. Unaware of their neoteny, Auguste Duméril was surprised when, instead of the axolotl, he found in the vivarium a new species, similar to the salamander. This discovery was the starting point of research about neoteny. It is not certain that Ambystoma velasci specimens were not included in the original shipment. Vilem Laufberger in Prague used thyroid hormone injections to induce an axolotl to grow into

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1128-628: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

1222-419: A process called metamorphosis , in which they lose their gills and start living on land. However, the axolotl is unusual in that it has a lack of thyroid-stimulating hormone , which is needed for the thyroid to produce thyroxine in order for the axolotl to go through metamorphosis; therefore, it keeps its gills and lives in water all its life, even after it becomes an adult and is able to reproduce . Neoteny

1316-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

1410-459: A small native population, there is a large loss of genetic diversity. This lack of genetic diversity can be dangerous for the remaining population, causing an increase in inbreeding and a decrease in general fitness and adaptive potential. It ultimately raises the axolotl's risk for extinction, something that they are already in danger of. Studies have found indicators of a low interpopulation gene flow and higher rates of genetic drift. These are likely

1504-910: A survival mechanism, in aquatic environments only of mountain and hill, with little food and, in particular, with little iodine. In this way, salamanders can reproduce and survive in the form of a smaller larval stage, which is aquatic and requires a lower quality and quantity of food compared to the big adult, which is terrestrial. If the salamander larvae ingest a sufficient amount of iodine, directly or indirectly through cannibalism , they quickly begin metamorphosis and transform into bigger terrestrial adults, with higher dietary requirements. In fact, in some high mountain lakes there live dwarf forms of salmonids that are caused by deficiencies in food and, in particular, iodine, which causes cretinism and dwarfism due to hypothyroidism , as it does in humans. xenbase provides limited support (BLAST, JBrowse tracks, genome download) for Axolotls. Axolotls are only native to

1598-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

1692-662: A terrestrial adult salamander. The experiment was repeated by Englishman Julian Huxley , who was unaware the experiment had already been done, using ground thyroids. Since then, experiments have been done often with injections of iodine or various thyroid hormones used to induce metamorphosis. Many other species within the axolotl's genus are also either entirely neotenic or have neotenic populations. Sirens and Necturus are other neotenic salamanders, although unlike axolotls, they cannot be induced to metamorphose by an injection of iodine or thyroxine hormone. Neoteny has been observed in all salamander families in which it seems to be

1786-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

1880-423: A two-stroke manner that pumps air from the mouth to the lungs, and with four-stroke that reverses this pathway with compression forces. Axolotls have four pigmentation genes; when mutated, they create different color variants. The normal wild-type animal is brown or tan with gold speckles and an olive undertone. The five most common mutant colors are listed below. In addition, there is wide individual variability in

1974-472: A very unhealthily reduced appetite. Temperatures at approximately 16 °C (61 °F) to 18 °C (64 °F) are suggested for captive axolotls to ensure sufficient food intake; stress resulting from more than a day's exposure to lower temperatures may quickly lead to disease and death, and temperatures higher than 24 °C (75 °F) may lead to metabolic rate increase, also causing stress and eventually death. Chlorine , commonly added to tapwater ,

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2068-428: Is a paedomorphic salamander closely related to the tiger salamander . It is unusual among amphibians in that it reaches adulthood without undergoing metamorphosis . Instead of taking to the land, adults remain aquatic and gilled . The species was originally found in several lakes underlying what is now Mexico City , such as Lake Xochimilco and Lake Chalco . These lakes were drained by Spanish settlers after

2162-467: Is capable of the regeneration of entire lost appendages in a period of months, and, in certain cases, more vital structures, such as tail, limb, central nervous system, and tissues of the eye and heart. They can even restore less vital parts of their brains. They can also readily accept transplants from other individuals, including eyes and parts of the brain—restoring these alien organs to full functionality. In some cases, axolotls have been known to repair

2256-612: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

2350-916: Is harmful to axolotls. A single axolotl typically requires a 150-litre (40-US-gallon) tank. Axolotls spend the majority of the time at the bottom of the tank. Salts, such as Holtfreter's solution , are often added to the water to prevent infection. In captivity, axolotls eat a variety of readily available foods, including trout and salmon pellets, frozen or live bloodworms , earthworms , and waxworms . Axolotls can also eat feeder fish , but care should be taken as fish may contain parasites. Substrates are another important consideration for captive axolotls, as axolotls (like other amphibians and reptiles) tend to ingest bedding material together with food and are commonly prone to gastrointestinal obstruction and foreign body ingestion. Some common substrates used for animal enclosures can be harmful for amphibians and reptiles. Gravel (common in aquarium use) should not be used, and

2444-615: Is in contrast to hybridogenesis , where the maternal genomes are passed hemiclonally and the paternal genome is discarded every generation before the egg matures and reacquired from the sperm of another species. The nuclear DNA of the unisexuals generally comprises genomes from up to five species: the blue-spotted salamander ( A. laterale ), Jefferson salamander ( A. jeffersonianum ), small-mouthed salamander ( A. texanum ), streamside salamander ( A. barbouri ), and tiger salamander ( A. tigrinum ), denoted respectively as L, J, Tx, B, and Ti. This flexibility results in

2538-484: Is like that of most neotenic species—a high-altitude body of water surrounded by a risky terrestrial environment. These conditions are thought to favor neoteny . However, a terrestrial population of Mexican tiger salamanders occupies and breeds in the axolotl's habitat. The axolotl is carnivorous, consuming small prey such as mollusks, worms, insects, other arthropods, and small fish in the wild. Axolotls locate food by smell, and will "snap" at any potential meal, sucking

2632-408: Is more commonly used. In animals with functioning thyroid glands, iodine in the form of iodide is selectively gathered into the colloid of the thyroid. Inside the colloid, iodide is reduced to elemental iodine (I 2 ), which reacts with the tyrosyl residues of thyroglobulin . Two iodinated tyrosyl residues are conjugated together. When they are cleaved from the thyroglobulin chain, thyroid hormone

2726-471: Is mostly explained by a large fraction of repetitive sequences , but such repeated elements also contribute to increased median intron sizes (22,759 bp) which are 13, 16 and 25 times that observed in human (1,750 bp), mouse (1,469 bp) and Tibetan frog (906 bp), respectively. Most amphibians begin their lives as aquatic animals which are unable to live on dry land, often being dubbed as tadpoles . To reach adulthood , they go through

2820-496: Is obtained. In the absence of induced metamorphosis, larval axolotls start absorbing iodide into their thyroid glands at 30 days postfertilization. Larval axolotls do produce thyroid hormone from iodide, but the amount appears highly variable. Adult axolotls do not produce thyroid hormone unless metamorphism is triggered. An axolotl undergoing metamorphosis experiences a number of physiological changes that help them adapt to life on land. These include increased muscle tone in limbs,

2914-479: Is recommended that any sand consists of smooth particles with a grain size of under 1mm. One guide to axolotl care for laboratories notes that bowel obstructions are a common cause of death, and recommends that no items with a diameter below 3 cm (or approximately the size of the animal's head) should be available to the animal. There is some evidence that axolotls might seek out appropriately-sized gravel for use as gastroliths based on experiments conducted at

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3008-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

3102-436: Is the axolotl . They cannot produce thyroxine , so their only means of metamorphosis is mainly through the outside injection of it. This usually shortens the lifespan of the salamander. The presence of neotenic populations near those with large larvae has made it difficult to identify mole salamander species. The tiger salamander complex was previously considered a single species ranging from Canada to Mexico, falling under

3196-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

3290-466: Is the term for reaching sexual maturity without undergoing metamorphosis. The genes responsible for neoteny in laboratory animals may have been identified; however, they are not linked in wild populations, suggesting artificial selection is the cause of complete neoteny in laboratory and pet axolotls. The genes responsible have been narrowed down to a small chromosomal region called met1 , which contains several candidate genes. The axolotl's body has

3384-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

3478-824: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

3572-696: The International Union for Conservation of Nature and Natural Resources (IUCN) and is listed under Appendix II of the Convention on International Trade in Endangered Species (CITES). Axolotls are used extensively in scientific research due to their ability to regenerate limbs, gills and parts of their eyes and brains. Notably, their ability to regenerate declines with age, but it does not disappear. Axolotls keep modestly growing throughout their life and some consider this trait to be

3666-812: The Nahuatl language. They appear in the works of Mexican muralist Diego Rivera . In 2021, Mexico released a new design for its 50- peso banknote featuring an axolotl along with maize and chinampas on its back. It was recognized as "Bank Note of the Year" by the International Bank Note Society . HD 224693 , a star in the equatorial constellation of Cetus , was named Axólotl in 2019. The Pokémon Mudkip and its evolutions, added in Pokémon Ruby and Sapphire (2002), take some visual inspiration from axolotls. Additionally,

3760-512: The barred tiger salamander ( A. mavortium ) was elevated to species status—covering the tiger salamander populations in the western and central United States. Several distinct subspecies still exist in A. mavortium , which may be elevated to species status at some point in the future. The California tiger salamander ( A. californiense ) has also been elevated out of A. tigrinum, and is actually very distantly related to all other mole salamander species. The Plateau tiger salamander ( A. velasci )

3854-550: The conquest of the Aztec Empire , leading to the destruction of much of the axolotl's natural habitat. As of 2020 , the axolotl was near extinction due to urbanization in Mexico City and consequent water pollution , as well as the introduction of invasive species such as tilapia and perch . It is listed as critically endangered in the wild, with a decreasing population of around 50 to 1,000 adult individuals, by

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3948-419: The nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

4042-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

4136-503: The Mexican Central Valley. Although the native axolotl population once extended through most of the lakes and wetlands that make up this region, the native habitat is now limited to Lake Xochimilco as a result of the expansion of Mexico City. Lake Xochimilco is not a large body of water, but rather a small series of artificial channels, small lakes, and temporary wetlands. Lake Xochimilco has poor water quality, caused by

4230-461: The Nile tilapia and common carp. These invasive fish species threaten axolotl populations by eating their eggs or young and by out-competing them for natural resources. The presence of these species has also been shown to change the behavior of axolotls, causing them to be less active to avoid predation. This reduction in activity greatly impacts the axolotls foraging and mating opportunities. With such

4324-835: The Pokémon Wooper , added in Pokémon Gold, Silver and Crystal (1999), is directly based on an axolotl. The looks of the dragons Toothless and The Night Fury in the How to Train Your Dragon movies are based on axolotls. They were also added to the video game Minecraft in 2020. It is following Mojang Studios ' trend of adding endangered species to the game to raise awareness. They were also added to its spin-off Minecraft: Dungeons in 2022 and are available in Lego Minecraft . An anthropomorphic Axolotl named Axo

4418-532: The Universidad Nacional Autonoma de Mexico (UNAM) has built up a population of more than 100 captive-bred individuals. These axolotls are mostly used for research by the lab but plans of a semi-artificial wetland inside the university have been established and the goal is to establish a viable population of axolotls within it. Studies have shown that captive-bred axolotls that are raised in a semi-natural environment can catch prey, survive in

4512-548: The University of Manitoba axolotl colony. As there is no conclusive evidence pointing to gastrolith use, gravel should be avoided due to the high risk of impaction . The species is named after the Aztec deity Xolotl , the god of fire and lightning, who transformed himself into an axolotl to avoid being sacrificed by fellow gods. They continue to play an outsized cultural role in Mexico. Axólotl also means water monster in

4606-434: The absorption of gills and fins into the body, the development of eyelids, and a reduction in the skin's permeability to water, allowing the axolotl to stay more easily hydrated when on land. The lungs of an axolotl, though present alongside gills after reaching non-metamorphosed adulthood, develop further during metamorphosis. An axolotl that has gone through metamorphosis resembles an adult plateau tiger salamander , though

4700-473: The axolotl differs in its longer toes. Among hobbyists, the process of artificially inducing metamorphosis can often result in death during or even following a successful attempt, and so casual hobbyists are generally discouraged from attempting to induce metamorphosis in pet axolotls. Morphed pet axolotls should be given solid footholds in their enclosure to satisfy their need for land. They should not be given live animals as food. Six adult axolotls (including

4794-429: The axolotl's neural tube, unlike the frog's, is not hidden under a layer of superficial epithelium . There are also mutations affecting other organ systems some of which are not well characterized and others that are. The genetics of the color variants of the axolotl have also been widely studied. The feature of the axolotl that attracts most attention is its healing ability: the axolotl does not heal by scarring and

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4888-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

4982-415: The capacity to go through metamorphosis if given the necessary hormone, but axolotls do not produce it, and must be exposed to it from an external source, after which an axolotl undergoes an artificially-induced metamorphosis and begins living on land. In laboratory conditions, metamorphosis is reliably induced by administering either the thyroid hormone thyroxine or thyroid-stimulating hormone . The former

5076-412: The complexity of their genomes. The offspring of a single mother may have different genome complements; for example, a single egg mass may have both LLJJ and LJJ larvae. Despite the complexity of the nuclear genome, all unisexuals form a monophyletic group based on their mitochondrial DNA . The maternal ancestor of the unisexual ambystomatids was most closely related to the streamside salamander , with

5170-1365: The contraction of a Greek phrase meaning "to cram into the mouth," but others have not found this explanation convincing. In the absence of clear evidence that Tschudi committed a lapsus , the name given in 1839 stands. This genus contains 32 species , listed below, the newest being A. bishopi . Some Ambystoma species are Terrestrial , others are neotenic , and some species have established populations of both neotenic and terrestrial forms. Dugès , 1895 Taylor , 1940 ( Brandon and Krebs , 1984) Cope , 1886 Kraus & Petranka, 1989 Pauly , Piskurek & Shaffer , 2007 ( Taylor , 1940) Gray , 1853 Cope, 1868 ( Dugès , 1870) Dixon , 1963 ( Baird , 1859) Taylor , 1944 ( Green , 1827) Hallowell , 1856 Taylor , 1943 ( Taylor , 1940) Bishop, 1928 Baird , 1950 ( Shaw , 1802) Baird , 1850 ( Shaw and Nodder , 1798) ( Gravenhorst , 1807) Taylor , 1940 Taylor , 1940 Taylor , 1941 Webb , 2004 Holbrook , 1838 Brandon , Maruska, and Rumph, 1982 Matthes, 1855 ( Green , 1825) ( Dugès , 1888) In addition, two groups of unisexual hybrid populations are sometimes named under their own species: [REDACTED] Data related to Ambystomatidae at Wikispecies [REDACTED] Media related to Ambystoma at Wikimedia Commons Genus The composition of

5264-482: The eggs then discard the sperm genome and develop asexually (i.e., gynogenesis , with premeiotic doubling ); however, they may incorporate the genome from the sperm into the resulting offspring. Sperm incorporation commonly takes the form of genome addition (resulting in ploidy elevation in the offspring), or genome replacement, wherein one of the maternal genomes is discarded. This unique mode of reproduction has been termed kleptogenesis by Bogart and colleagues. This

5358-464: The external gills, which prevent food from entering and allow particles to filter through. Axolotls have barely visible vestigial teeth, which develop during metamorphosis. The primary method of feeding is by suction , during which their rakers interlock to close the gill slits. External gills are used for respiration, although buccal pumping (gulping air from the surface) may also be used to provide oxygen to their lungs. Buccal pumping can occur in

5452-416: The food into their stomachs with vacuum force. Today, the axolotl is still used in research as a model organism , and large numbers are bred in captivity. They are especially easy to breed compared to other salamanders in their family, which are rarely captive-bred due to the demands of terrestrial life. One attractive feature for research is the large and easily manipulated embryo , which allows viewing of

5546-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

5640-433: The full development of a vertebrate. Axolotls are used in heart defect studies due to the presence of a mutant gene that causes heart failure in embryos. Since the embryos survive almost to hatching with no heart function, the defect is very observable. The axolotl is also considered an ideal animal model for the study of neural tube closure due to the similarities between human and axolotl neural plate and tube formation;

5734-737: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

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5828-586: The growth of Mexico City . The axolotl is currently on the International Union for Conservation of Nature's annual Red List of threatened species. Non-native fish, such as African tilapia and Asian carp , have also recently been introduced to the waters. These new fish have been eating the axolotls' young, as well as their primary source of food. Axolotls are members of the tiger salamander, or Ambystoma tigrinum , species complex , along with all other Mexican species of Ambystoma . Their habitat

5922-412: The lake and a reduction of habitat quality for axolotls. The pesticides used contain chemical compounds that studies show to sharply increase mortality in axolotl embryos and larvae. Of the surviving embryo and larvae, there is also an increase of morphological, behavior, and activity abnormalities. Another factor that threatens the native axolotl population is the introduction of invasive species such as

6016-633: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

6110-472: The largest of the mole salamanders, and have very large larvae. All populations have similar lifestyles, and their lifecycles are identical. However, when one looks at tiger salamander populations distant from each other, different species within this complex become apparent. The ranges of these potential species overlap, and hybridization occurs, blurring the lines between species. Several subspecies of A. tigrinum were named to deal with this problem. Recently,

6204-462: The lineages by matings with A. laterale . Ambystoma mexicanum , a neotenic salamander with exceptional regenerative capabilities is one of the principal models for studying limb regeneration. Limb regeneration involves the propagation of a mass of low differentiated and highly proliferative cells termed the blastema . During limb regeneration, blastema cells experience DNA double-strand breaks and thus require homologous recombination ,

6298-403: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Axolotl This is an accepted version of this page The axolotl ( / ˈ æ k s ə l ɒ t əl / ; from Classical Nahuatl : āxōlōtl [aːˈʃoːloːtɬ] ) ( Ambystoma mexicanum )

6392-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

6486-455: The name A. tigrinum . Despite differences in coloration and larvae, tiger salamanders were found throughout their unbroken range , which made it difficult to delineate subspecies, let alone elevate any populations to species status. In morphological terms, tiger salamanders are all very similar, with large heads, small eyes, and thick bodies. This is probably because tiger salamanders have the primitive morphology of mole salamanders. They are also

6580-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

6674-418: The original hybridization likely occurring 2.4~3.9 million years ago, making it the oldest known lineage of all-female vertebrates. The hybridization was most probably with an A. laterale . All known unisexuals have at least one A. laterale genome and this is thought to be essential for unisexuality. However, the A. laterale genome has been replaced several times, independently, in each of

6768-495: The parent of most of the neotenic species, which raises the possibility that A. velasci is paraphyletic, and may be broken up into more species in the future. Unisexual (all-female) populations of ambystomatid salamanders are widely distributed across the Great Lakes region and northeastern North America. The females require sperm from a co‑occurring, related species to fertilize their eggs and initiate development. Usually

6862-633: The presence of cells from the different limb axes. A wound epidermis is quickly formed by the cells to cover up the site of the wound. In the following days, the cells of the wound epidermis divide and grow quickly forming a blastema, which means the wound is ready to heal and undergo patterning to form the new limb. It is believed that during limb generation, axolotls have a different system to regulate their internal macrophage level and suppress inflammation , as scarring prevents proper healing and regeneration. However, this belief has been questioned by other studies. The axolotl's regenerative properties leave

6956-608: The presence of deleterious, or harmful, genes within a population. The detection of introgressed tiger salamander ( A. tigrinum ) DNA in the laboratory axolotl population raises further concerns about the suitability of the captive population as an ark for potential reintroduction purposes. There has been little improvement in the conditions of the lake or the population of native axolotls. Many scientists are focusing their conservation efforts on translocation of captive-bred individuals into new habitats or reintroduction into Lake Xochimilco. The Laboratorio de Restauracion Ecologica (LRE) in

7050-541: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

7144-500: The regenerative processes that occur for axolotls. The 32 billion base pair long sequence of the axolotl's genome was published in 2018 and was the largest animal genome completed at the time. It revealed species-specific genetic pathways that may be responsible for limb regeneration. Although the axolotl genome is about 10 times as large as the human genome , it encodes a similar number of proteins, namely 23,251 (the human genome encodes about 20,000 proteins). The size difference

7238-416: The region's aquaculture and agriculture demands. It is also maintained by inputs of only partially treated wastewater. Water quality tests reveal a low nitrogen-phosphorus ratio and a high concentration of chlorophyll a, which are indicative of an oxygen-poor environment that is not well-suited for axolotls. In addition, the intensive use of pesticides from agriculture around Lake Xochimilco causes run off into

7332-577: The relative size and thickness of their melanophores. The axolotl is native only to the freshwater of Lake Xochimilco and Lake Chalco in the Valley of Mexico . Lake Chalco no longer exists, having been drained as a flood control measure, and Lake Xochimilco remains a remnant of its former self, existing mainly as canals. The water temperature in Xochimilco rarely rises above 20 °C (68 °F), although it may fall to 6–7 °C (43–45 °F) in

7426-564: The result of multiple “bottleneck” incidents in which events that kill off several individuals of a population occur and sharply reduce the genetic diversity of the remaining population. The offspring produced after bottleneck events have a greater risk of showing decreased fitness and are often less capable of adaptation down the line. Multiple bottleneck events can have disastrous effects on a population. Studies have also found high rates of relatedness that are indicative of inbreeding. Inbreeding can be especially harmful as it can cause an increase in

7520-470: The same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but the French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or

7614-408: The scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of a species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in

7708-490: The size, frequency, and intensity of the gold speckling, and at least one variant develops a black and white piebald appearance upon reaching maturity. Because pet breeders frequently cross the variant colors, double homozygous mutants are common in the pet trade, especially white/pink animals with pink eyes that are double homozygous mutants for both the albino and leucistic trait. Axolotls also have some limited ability to alter their color to provide better camouflage by changing

7802-497: The south, and tiger salamanders) can reach their adult size before undergoing metamorphosis . During metamorphosis, the gills of the larvae disappear, as do the fins. Their tails, skin, and limbs become thicker, and the eyes develop lids. Their lungs become fully developed, allowing for a fully terrestrial existence. Some species of mole salamanders (as well as populations of normally terrestrial species) are neotenic (retaining their larval form into adulthood). The most famous example

7896-455: The species as the perfect model to study the process of stem cells and its own neoteny feature. Current research can record specific examples of these regenerative properties through tracking cell fates and behaviors, lineage tracing skin triploid cell grafts, pigmentation imaging, electroporation, tissue clearing and lineage tracing from dye labeling. The newer technologies of germline modification and transgenesis are better suited for live imaging

7990-442: The species. Terrestrial adults spend most of their lives underground in burrows , either of their own making or abandoned by other animals. Some northern species may hibernate in these burrows throughout the winter. They live alone and feed on any available invertebrate . Adults spend little time in the water, only returning to the ponds of their birth to breed. All mole salamanders are oviparous and lay large eggs in clumps in

8084-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

8178-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

8272-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

8366-576: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

8460-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

8554-458: The water. Their fully aquatic larvae are branchiate, with three pairs of external gills behind their heads and above their gill slits . Larvae have large caudal fins , which extend from the back of their heads to their tails and to their cloacae . Larvae grow limbs soon after hatching, with four toes on the fore arms, and five toes on the hind legs. Their eyes are wide-set and lack true eyelids. The larvae of some species (especially those in

8648-411: The wild, and have moderate success in escaping predators. These captive-bred individuals can be introduced into unpolluted bodies of water or back into Lake Xochimilco to establish or re-establish a wild population. The axolotl is a popular exotic pet like its relative, the tiger salamander ( Ambystoma tigrinum ). As for all poikilothermic organisms, lower temperatures result in slower metabolism and

8742-416: The winter, and perhaps lower. Surveys in 1998, 2003, and 2008 found 6,000, 1,000, and 100 axolotls per square kilometer in its Lake Xochimilco habitat, respectively. A four-month-long search in 2013, however, turned up no surviving individuals in the wild. Just a month later, two wild ones were spotted in a network of canals leading from Xochimilco. The wild population has been put under heavy pressure by

8836-403: Was elevated out of A. tigrinum through genetic analysis in 1997. All accounts referring to the axolotl ( A. mexicanum ) as a close relative of A. tigrinum are now considered wrong, as they are now separated by both geography and many species between. Instead, it is A. velasci , which shares the axolotl's habitat, and is probably closely related to it. The Plateau tiger salamander was probably

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