Axolotl | San Diego Zoo Animals & Plants

Shrouded in mystery, and defying typical biological laws like metamorphosis, the axolotl (pronounced AX-oh-lot-ul), a type of salamander, keeps its webbed feet firmly placed in infancy throughout its life.

Unlike other salamanders, axolotls are neotenic, meaning they keep juvenile characteristics into adulthood. Axolotls remain aquatic (like larvae) their entire life. Though they develop functional lungs, they use prominent, feathery gills to breathe underwater. Like youngsters, they retain external gills, a tail, and a body fin, and lack movable eyelids.

Once naturally occurring in a series of lakes and wetlands in the Mexican Central Valley, axolotl populations now live in just three isolated sites in the southern part of Mexico City, Mexico. Descended from tiger salamanders, axolotls are relatively “young," having inhabited central Mexico for only about the last 10,000 years, according to some experts. Indigenous to lakes Xochimilco and Chalco along the southern edge of the Basin of Mexico, much of their suitable habitat has been drained. The Xochimilco-Chalco basin, once about 77 square miles (200 square kilometers) of marshes, swamps, and lagoons, was significantly reduced 85 years ago when drainage projects were completed.

Many consider axolotls charismatic, and they're deeply connected to Mexican history, culture, and identity. That said, little information exists about the ecology of axolotl populations. This is surprising, given their popularity. However, their small and generally inaccessible populations make it difficult to learn about their behavior. What is known about axolotls has been primarily learned from populations cared for by people.

Axolotls have dark coloring to match their muddy lake habitats and can shift their hue a few shades lighter or darker as needed for camouflage. Although naturally dark, axolotls can be many colors: white (albino), pink, golden, or multicolored.

Axolotls have another icredible ability: they can regenerate their limbs, lungs, heart, jaws, spines, and even parts of their brain! Scientists have found that axolotls can regrow a new limb five times perfectly, in a few weeks—without even a scar. Every tissue is replaced: skin, bone, cartilage, muscle, and stem cells. Other organs can regenerate countless times and be completely functional. Naturally, scientists would like to understand this remarkable ability and explore how similar regenerative thereapies could help people. It is said that axolotls are over 1,000 times more resistant to cancer than mammals—another superpower worth investigating.

An axolotl can reach 12 inches in length, but on average grows to about 9 inches. They have broad, flat bodies with large heads donning signature feathery gills. Their mouths are often bent into a slight grin or are otherwise expressive. Round, dark eyes with yellow, iridescent irises take in the murky environment while lizard-like limbs carry it along the lake bottom. Axolotls weigh about as much as a deck of cards. In a pinch, they can move an astonishing 10 miles per hour (15 kilometers per hour).