Mexican axolotls, or Ambystoma mexicanum, are a species of salamander now found only in the lake complex Xochimilco in Mexico City. The name ‘axolotl’ is a word in the Aztec language Nahuatl. It is often translated as connected to Xolotl, the Aztec god of death, lightning, and fire. Xolotl is said to have turned into a salamander. Another translation says that ‘axolotl’ means ‘water dog’, as ‘atl’ means water and ‘xolotl’ can also mean dog. There are many other translations as well.
Mexican axolotls are neotenic salamanders, meaning they do not complete the usual metamorphosis of amphibious animals: they never develop the lungs that would let them live on land and are solely aquatic, even as adults.
Axolotls can be up to 30 centimeters long. They have gills that protrude from the back of their head, and four gill slits hidden beneath the outer ones. They lack eyelids. They also have short legs with four fingers on their front legs, and five on their back. They can live up to 25 years but rarely live more than 15. Mexican axolotls have almost hidden teeth. They have the ability to regrow some body parts, and are studied by scientists for this fact, in the hope of applying this technology to humans. Interestingly, their heart has only three chambers, instead of mammals’ four, and they also differ from mammals in that they are cold blooded.
Normally, mexican axolotls would be brown with golden flecks, but there are for mutated color variations: leucism (pale pink with black eyes), albino (golden with golden eyes), axanthic (gray with black eyes) and melanoid (all black without golden speckling or olive tone). There is also variation in size, frequency and intensity of gold speckle and a weather or not a black and white slate appears in adulthood. Pet breeders often cross these colors to create new mixes.
A captive axolotl. Image courtesy of Joel Sartore.
In the wild, Mexican axolotls are carnivorous and eat worms, insects, small fish, mollusks, insects, spiders, and each other. They find their food by smell and then suck it into their stomach. They have relatively few natural predators and were once the top of the food chain.
However, in the 1970s and 80s, tilapia and carp were introduced to provide more protein for people in the area. These fish, as well as some birds, eat young axolotls. Humans also prey on axolotls, both for food and as pets: they are charismatic and easy to care for.
Mexican Axolotls are listed as critically endangered and their population is on the decline. In 1998, 6,000 were found in a square kilometer. In 2003, 1,000, and in 2008, 100. In 2013 a search produced no axolotls, but two individuals were later found.
Mexican axolotls are nearing extinction because of urbanization and resultant pollution of their one remaining lake habitat, Lake Xochimilco. They once lived in Lake Chalco, one of the five ‘great lakes’ of Mexico City that were drained, except Xochimilco, in the 1970s to prevent flooding and allow expansion. Mexico City is now working on conservation for the Mexican axolotl via construction of shelters and conservation of their habitat.
Rehm, J. (2019, September 19). Axolotls: The Adorable, Giant Salamanders of Mexico. Retrieved January 18, 2021, from https://www.livescience.com/axolotl-facts.html
Mexican Axolotls: Characteristics, reproduction, hábitats and more. (2018, December 09). Retrieved January 18, 2021, from http://ourmarinespecies.com/c-other-species/mexican-axolotls/
Axolotl: National Geographic. (2018, September 21). Retrieved January 18, 2021, from https://www.nationalgeographic.com/animals/amphibians/a/axolotl/
Cover image courtesy of Our Marine Species