In its natural state, the axolotl was endemic to Lake Xochimilco, which is located 20km southeast of Mexico City. The axolotl has become a model organism and companion animal for several years, it is therefore successfully reproduced in captivity but in the wild it is close to extinction.
Over the years, the number of axolotls found has been found to be less and less. On the contrary, the number of exotic fish, such as carp, which feed on eggs and larvae of this species is increasing in the lake of Xochimilco, subject to polluting discharges.
A recent scientific investigation, in 2014, did not reveal axolotls, although animals caught in the wild are still found in the local market, indicating that fishermen still know where to find them. It was once consumed as a local delicacy until it was considered unsafe and then fishing was prohibited.
If damaged, this animal is capable of regenerating without scars, limbs, lungs, spinal cord and even parts of the brain. It seems that this very particular feature derives from cells very similar to the adult stem cells present in mammals.
Neoteny has been observed in all families of urodel amphibians such as salamander and axolotl in which it appears to be a survival mechanism only in low-nourishing and particularly low-iodine mountain and hill aquatic environments.
In this way the salamanders can reproduce and survive in the small and less expensive form of the larval stage, which being aquatic requires food of less quality and quantity than the larger adult, which is terrestrial and carnivorous.
If salamander larvae ingest a sufficient amount of iodine, directly or indirectly through cannibalism, they rapidly begin metamorphosis and transform into larger terrestrial adult forms with greater food demands. The head is broad and the eyes have no lids.
The limbs are poorly developed and have long and thin fingers. Males differ from females for the large genital canal while females are able to fill their bodies with eggs at the time of reproduction. Three pairs of gills are located behind the head and are used to move and oxygenate the water, while four external gills aligned with the front gills are hidden in the back.
Axolotls have barely visible rudimentary teeth that could have been born during a process of metamorphosis of the animal: these animals feed mainly by sucking thanks to the action of the front gills that are used to block the prey. The rear gills are used for breathing, although the axolotl can also breathe by swallowing air from the outer surface.