Just as the “so i herd u liek mudkipz” meme has popularized the water type starter, Mudkip, from the beloved Ruby, Sapphire, and Emerald Pokémon games (and, recently Omega Ruby and Alpha Sapphire), the internet seems to have somewhat familiarized the public with a peculiar and endangered salamander.
The Axolotl (Ambystoma mexicanum) lives exclusively in the fragmented remains of Central Mexico’s Lake Chalco and was once present in Lake Xochimilco before it was drained. These salamanders can come in a variety of different colors, two of them being wild type and the other two present in mutations. The wild colors are brown and black, while the mutant colors are leucistic and albino. Although both the leucistic and albino axolotls are varying shades of pinkish white, the albino has pink eyes and the leucistic has black eyes. They are closely related to tiger salamanders, sharing the same genus, and in fact look very similar to the larvae of tiger salamanders. Unlike other salamanders, axolotls normally never undergo metamorphosis into an adult form. This does not mean that they are not sexually mature, however. The average axolotl reaches maturity at 18-24 months of age with a typical length of around nine inches. They have both rudimentary lungs and gills so they are able to take oxygen from the water and gulp air at the surface. The gills are arranged on three stalks on each side behind the head. An axolotl also retains fins running from the end of its body to the tip of the tail.
Retaining larval characteristics throughout life is called neoteny. Other salamanders can become neotinic if conditions in the environment put an unusual level of stress on the animal, but the axolotl is exclusively neotinic within its species. On extremely rare occasions, axolotls will progress to adult form. They most often remain strictly aquatic, though. They are naturally top predators in the areas they inhabit and feed on mollusks, crustaceans, water insects, and small fish. Since they are neotinic, their teeth are not fully developed and are only rough stumps in their jaws. They use these tooth stumps to grasp a prey item and position it before swallowing it whole. Unfortunately, since the introduction of large, nonnative fish, there is more competition for food and occasional predation upon axolotls by these fish. Additionally, axolotls are sold in markets as a delicacy which further reduces their population and they are now a red listed species that is critically endangered.
Another very intriguing aspect of the axolotl is its Wolverine-like ability to heal itself. This trait has made it one of the most heavily studied salamanders in the world. Axolotls can completely regenerate their limbs, spinal cords, and even some organs in a matter of a couple months. The younger the salamander, the faster it heals. Older axolotls can still regenerate, but it takes much longer. The oldest axolotl in captivity, named Tiger Girl, in the Axolotl Center of Hanover, Germany was 16 years old (as of 2010) and it took her a year to grow back a leg that was bitten off by one of her tank mates. This research center is dedicated to the conservation of axolotls and studies their regeneration abilities in a humane, minimum stress environment. Researchers will anesthetize a salamander and cut off part of its limb to study the healing process. This doesn’t hurt the animal due to its incredible healing abilities and it is well cared for and eventually left to a life of retirement with no more testing.
Research institutions like the one in Hanover are helping to strengthen the international breeding program of axolotls and conserve this very remarkable and interesting species. It may give us clues about how to help humans who are injured to heal more effectively, such as burn victims. It is not only a fascinating animal, but also a valuable source of information for science and medicine that is imperative to save.
1. Luis Zambrano et al. “Ambystoma mexicanum”. The IUCN Red List of Threatened Species, 2015. Web. 23 June, 2015. http://www.iucnredlist.org/details/1095/0
2. Taurog, Alvin, et al. “The role of TRH in the neoteny of the Mexican axolotl (Ambystoma mexicanum).” General and comparative endocrinology 24.3 (1974): 267-279.
3. Kragl, Martin, et al. “Cells keep a memory of their tissue origin during axolotl limb regeneration.” Nature 460.7251 (2009): 60-65.
4. Hamm, Magdalena. “Miracle Healer.” Speigel Online International. Speigel, 2 Dec. 2010. Web. 23 June 2015. <http://www.spiegel.de/international/zeitgeist/miracle-healer-scientists-attempt-to-crack-secret-code-of-the-axolotl-a-732283.html>.
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