The Unique Abilities of the Axolotl

​Extreme Animals Alive is a special exhibition at the Houston Museum of Natural Science, a 501(c)(3) nonprofit organization. The unique exhibit features live animals with "superpowers," including the ability to change shape, glow, or even control the minds of other animals. One of the exhibit's most interesting creatures is the axolotl.

The axolotl is a species of paedomorphic mole salamander. Axolotls differ from many other amphibians in that they mature into their adult form without going through a metamorphic period. Furthermore, the adults remain fully aquatic and sport external gills.

Adult axolotls reach sexual maturity between 18 and 27 months, at which point they may reach up to 18 inches in length, though 9 to 12 inches is more common. They closely resemble salamander larvae, partly because they do not lose their external gills, like most salamander species. Axolotls also have vestigial teeth, which usually only occur in salamanders going through metamorphosis.

Wild axolotls usually appear brown or tan with a lighter undertone. However, they can change their color for camouflage, and researchers have noted several common color mutations, including pale pink with black eyes and white with red eyes.

The species originated in a system of lakes and wetlands in the Mexican highlands, along with smaller lakes throughout Xochimilco, Chalco, and other nearby waterways. Spanish settlers destroyed much of the animal's habitat following the conquest of the Aztec Empire, leaving the remaining population confined to areas around Mexico City. Despite losing a significant stretch of habitat, axolotls persisted in sufficient numbers to become a staple of the native Mexican diet during colonial times.

In modern times, the axolotl continues to face many challenges, including water pollution and threats from invasive species such as carp and tilapia. As a result, the axolotl qualifies as a Critically Endangered species, meaning it is nearly extinct in the wild. According to the International Union for Conservation of Nature, just 50 to 1,000 axolotls remain in the wild.

In captivity, meanwhile, the axolotl maintains a sizable population, largely due to the global scientific community's fascination with the animal's ability to regenerate limbs, gills, and even its eyes, heart, and central nervous system, including parts of the brain. Rather than scarring, the axolotl's body regenerates tissue over months. Researchers have also discovered that the axolotl's body readily accepts transplants from other individuals.

Axolotl regeneration can have several results. For example, if an animal's limb is damaged, the body may simultaneously grow a new limb and repair the original limb, resulting in an axolotl with extra arms or legs. Axolotls can regenerate more easily in youth, but do not lose the ability with age. While scientists do not fully understand the animal's ability to regenerate, they sometimes attribute it to the axolotl's indeterminate growth, meaning its body continues to grow throughout its lifetime.

As mentioned, the axolotl also attracts scientists, researchers, and animal lovers for its neoteny. Many amphibian species begin life as fully aquatic animals, undergo metamorphosis, and then lose their gills as they assume a more terrestrial form. The term "neoteny" means that the axolotl reaches sexual maturity without undergoing metamorphosis, maintaining its gills and living its entire life in water.

Joel Bartsch

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