Axolotl (Ambystoma mexicanum) - Wiki
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The Axolotl (Ambystoma mexicanum) is a large Mexican salamander noted for its demonstration of neoteny, remaining in its aquatic larval form even as a sexually mature adult and not undergoing metamorphosis into a terrestrial form. The name axolotl comes from the Nahuatl language; in Spanish it is called ajolote.
Also, axolotls have cousins often referred to as "mud puppies" that appear similar and are found throughout Mexico and in many places in the southern United States. Axolotls usually live more than 10 - 12 years.
A fully grown axolotl, at age 18???24 months, ranges in length from 150???450 mm (6???18 inches), although a size close to 230 mm (9 inches) is most common and greater than 300 mm (12 inches) is rare. They have distinctive "fern-like" gill structures that are not covered (as are gills in fish and in frog tadpoles) ??? usually 3 stalks on each side of the head; the colour of the fern-like part varies although the usual colour is red and it has been known that species with a diet high in red meat gain red gills; axolotls also breathe through the skin and possess lungs. Axolotls have tiny teeth which are hardly noticeable and are used to grip food rather than to tear and chew it. They are also known to have a fast regeneration rate where they can regrow limbs and organs.
Axolotls are very closely related to Tiger Salamanders (Ambystoma tigrinum). In colour they range from albino or white (leucistic) to black, through greys, tans and browns. Wild axolotls are rarely white, though all leucistic (white with black eyes) axolotls are descended from a single mutant male brought to Paris in 1863 in a shipment to the Jardin des Plantes in the city. The true albino mutant common in labs and pet stores was created in an American laboratory in the 1950s through hybridization with an albino Tiger Salamander. No axolotls commercially available today are wild caught (since doing so is strictly forbidden), the majority being descended from these same research specimens, even in the pet trade.
The axolotl is only native to Lake Xochimilco and Lake Chalco in central Mexico. Unfortunately for the axolotl, Lake Chalco no longer exists as it was drained by humans to avoid periodic flooding, and Lake Xochimilco remains a diminished glimpse of its former self, existing mainly as canals. The water temperature in Xochimilco rarely rises above 20°C (68°F), though it may fall to 6 or 7°C (43°F) in the winter, and perhaps lower.
The wild population has been put under heavy pressure by the growth of Mexico City. Axolotls are also sold as food in Mexican markets, and were a staple in the Aztec diet. They are currently listed by CITES as an endangered species, and by IUCN as critically endangered in the wild, with a decreasing population.
Axolotls exhibit a property called neoteny, meaning that they reach adulthood without undergoing metamorphosis. Some axolotls metamorphose, although they do so rarely, and usually only after an injection of iodine or shots of thyroxine hormone. Another method for inducing transformation, though one that is very rarely successful, involves removing an axolotl in good condition to a shallow tank in a vivarium and slowly reducing the water level so that the axolotl has difficulty submerging, and eventually is unable submerge at all; it will then stop using its gills to breathe and use its lungs. It will then, over a period of weeks, slowly metamorphose into an adult salamander. During transformation, the air in the vivarium must remain moist, and the maturing axolotl sprayed with a fine mist of pure water. The odds of the animal being able to metamorphose via this method are extremely small, and most attempts at inducing metamorphosis lead to death. Spontaneous metamorphosis has been known to occur very rarely, but attempts to do so artificially are best left to trained scientists. An inability to produce the necessary hormones required for metamorphosis on their own results in such a neotenic existence. Artificial metamorphosis also dramatically shortens the axolotl's lifespan, if they survive the process. A neotenic axolotl will live an average of 10???15 years (though an individual in Paris is credited with achieving 25 years), while a metamorphosed specimen will scarcely live past the age of five. The adult form resembles the adult Tiger Salamander, supporting the theory that the two species are closely related.
Jardin des Plantes story
The first imported axolotls in Europe during the 19th Century were placed in the "Jardin des Plantes" in Paris. Unaware of their neoteny, Auguste Dum??ril 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.
Vilem Laufberger's experiment
Vilem Laufberger did a famous experiment in Germany concerning the axolotl. Using thyroid hormone injections, he persuaded an axolotl to grow into a fully adult salamander of a species that no one had ever seen. This is because the axolotl is a juvenile form of an amphibian that evolved to be sexually mature still in the 'infant'/larval stage. The experiment was repeated by the Englishman Julian Huxley, who was unaware the experiment had already been done. Since then, experiments have been done often with injections of iodine or various thyroid hormones used to induce metamorphosis.
Uses in research
The axolotl is used in research and large numbers are bred in captivity. The feature of the salamander that attracts most attention is its healing ability: the axolotl does not heal by scarring and is capable of the regeneration of entire lost appendages in a period of months, and, in certain cases, more vital structures. Some have indeed been found restoring the 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 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. Another attractive feature, for research, is the large and robust embryos. Axolotls are especially easy to breed compared to other salamanders in their family, which are almost never captive bred.
The axolotl is carnivorous, consuming small prey such as worms, insects, and small fish in the wild.
In captivity, they can be fed a variety of readily available foods, including trout and salmon pellets, frozen or live bloodworms, earthworms, and waxworms on occasion. Beef heart is sometimes recommended, but is not a good choice for the animal as mammal proteins are not readily digestible. Small juveniles can be fed with Daphnia or brine shrimp until old enough for the larger foodstuffs. Axolotls locate food by smell, and will "snap" at any potential meal, sucking the food into their stomachs with vacuum force. This is why other animals may not be housed with axolotls (excluding adults with adults) as anything smaller will invariably end up in their mouths ??? even siblings. Fish can also nibble an axolotl's gill stalks and appendages while it is asleep, leading to infection.
Axolotls live at temperatures of 14???20°C (54???68°F), preferably 17???18°C (62???64°F). Lower temperatures slow down their metabolism, although temperatures around 10°C (50°F) are a panacea when it comes to treating disease. Higher temperatures can lead to stress and increased appetite; use of a cooling aggregate is strongly recommended. Tapwater should be treated with a dechlorinator before the animal is introduced into it, as chlorine is harmful. A single typical axolotl should be kept in a normal 10 U.S. gallon tank (44 litres) with around 150 mm (6 inches) of water. A full tank without a lid can lead to the animal "jumping ship" as it were. A power filter or underwater filter run by an airpump can be used, though water flow should be kept to a minimum to avoid stressing the animal. A 20% water change should be done every week, with debris being siphoned from the bottom. Small gravel should be avoided, as the axolotl can mistakenly ingest the rocks, leading to stress and gas. Floating plants should be provided for juveniles as a hiding place, and small caves should likewise be provided for adults. No light is necessary as axolotls are nocturnal. Axolotls will spend a majority of the time on the bottom of the tank (floating is a sign of stress and illness), so design accordingly.
In Japan, axolotls are known by the trademark WuperRuper (ウ???パ???ル???パ???). Originally the trademark was going to be registered as "SuperRuper", but since there are many trademarks starting with "super," the S was changed to a W so the name could be registered more quickly. It is said that the reason why they are not sold as "axolotl" is to avoid them being called "aho no r??toru", a similar-sounding Japanese phrase meaning "stupid old man."
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