6 Things You Don't Know About the Axolotl

While the axolotl is sometimes called the 'walking fish,' it is not actually a fish. Maslov Dmitry/Shutterstock

Amphibians aren't exactly charismatic, but, somehow, the axolotl attracts a lot of attention from people who may normally get squeamish around frogs. Perhaps it's their goofy smile and cute little frills that disarm people.

But these salamanders have a number of other special traits that may explain such keen interest all around, from scientists to conservationists to folks who just really love animals.

1. Axolotls Stay 'Babies' for Their Whole Lives

Axolotls are neotenic creatures meaning they achieve sexual maturity without losing any of their larval features. So while many amphibians, like the salamander, will eventually develop lungs and head to land, axolotls keep their trademark feathery external gills and remain aquatic. This also means that their teeth never develop and that they must rely on a suction method to consume food.

2. Axolotls, However, Can Be Given a Little Boost to Become 'Full' Salamanders

Scientists discovered that if an axolotl is given a shot of iodine, it will experience a rush of hormones that triggers the animal's growth processes, and it will "grow up" and resemble a mature tiger salamander, their closest relative. However, this is not the axolotl's natural state. "Grown-up" axolotls are typically listless and die about a year after the injection.

A gray-black axolotl at the bottom of a tank
Four genes affect the colors of axolotls. Faldrian/Wikimedia Commons

3. Axolotls Are Native to One Spot in the World (and They May Not Even Be There Any Longer)

These aquatic amphibians are only found in the wild in one location: Lake Xochimilco, located in southern Mexico City. They once also resided in Lake Chalco in central Mexico City, but that lake was drained to avoid flooding. Xochimilco is only a shell of it former self, reduced to a series of canals. Given Xochimilco's diminished state, the axolotl is considered critically endangered, and a 2013 survey failed to find any specimens in the wild.

4. Axolotls Come in a Variety of Color Patterns

Four genes control the pigmentation of axolotls and can result in significant variation in their colors patterns. Typically, however, they're brown or black with specks of gold or olive. The white axolotls with black eyes are more common as a result of breeding among pet traders, so they are rarely seen in the wild.

A white axolotl with black-blue eyes and pink frills
Axolotl have a huge genome that we are only now beginning to decipher. Ulmus Media/Shutterstock

5. Axolotls Can Regenerate Pretty Much Any Body Part

A number of amphibians are capable of regenerating limbs, but axolotls take this habit up a notch by regenerating jaws, spinal cords, skin and even portions of their brain. Axolotls can also receive organ transplants and will not reject the new organ. Their regenerative abilities are obviously of interest to researchers hoping to understand how it works and if this amazing quality could translate to humans.

6. Axolotls Have a Genome 10 Times the Size of the Human Genome

Across organisms, genomes have plenty of junk, repetitive DNA that doesn't have a function, and the axolotl, with its 32 billion DNA bases, is no different. But this also means sequencing and isolating the genes that may help us understand the creature's regenerative abilities is difficult. A 2018 study in Nature finally made a small breakthrough, identifying five genes that aren't present in other reptiles, amphibians or humans but are active in regenerating limbs.