The external gill rami are lined with filaments (fimbriae) to increase surface area for gas exchange. Three pairs of external gill stalks (rami) originate behind their heads and are used to move oxygenated water. Males are identified by their swollen cloacae lined with papillae, while females are noticeable for their wider bodies full of eggs. Their limbs are underdeveloped and possess long, thin digits. Their heads are wide, and their eyes are lidless. This is due to their neoteny evolution, where axolotls are much more aquatic than other salamander species. External gills are usually lost when salamander species mature into adulthood, although the axolotl maintains this feature. Axolotls possess features typical of salamander larvae, including external gills and a caudal fin extending from behind the head to the vent. Ī 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 were also sold as food in Mexican markets and were a staple in the Aztec diet. Axolotls are used extensively in scientific research due to their ability to regenerate limbs, gills and parts of their eyes and brains. They are listed as critically endangered in the wild, with a decreasing population of around 50 to 1,000 adult individuals, by the International Union for Conservation of Nature and Natural Resources (IUCN) and are listed under Appendix II of the Convention on International Trade in Endangered Species (CITES). Īs of 2020, wild axolotls were 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. Neither should they be confused with mudpuppies ( Necturus spp.), fully aquatic salamanders from a different family that are not closely related to the axolotl but bear a superficial resemblance. tigrinum), which are widespread in much of North America and occasionally become paedomorphic. These lakes were drained by Spanish settlers after the conquest of the Aztec Empire, leading to the destruction of much of the axolotl’s natural habitat.Īxolotls should not be confused with the larval stage of the closely related tiger salamander ( A. The species was originally found in several lakes underlying what is now Mexico City, such as Lake Xochimilco and Lake Chalco. Instead of taking to the land, adults remain aquatic and gilled. Axolotls are unusual among amphibians in that they reach adulthood without undergoing metamorphosis. The axolotl ( / ˈ æ k s ə l ɒ t əl/ from Classical Nahuatl: āxōlōtl ( listen)), Ambystoma mexicanum, is a paedomorphic salamander closely related to the tiger salamander.
Gyrinus mexicanus Shaw and Nodder, 1798.
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