The axolotl is sometimes called the Mexican walking fish, though it is not a fish at all. It is an amphibian and a type of salamander, and its closest relative is the tiger salamander. An axolotl lives in the water for its whole life. Axolotls are neotenic, which means they keep juvenile characteristics into adulthood, and they never go through metamorphosis and grow up to become adult salamanders. One idea is that axolotls stay in the water because their native lakes never dry up, so they never had to trade water traits for land ones. According to some experts, axolotls descended from tiger salamanders and have lived in central Mexico for only about the last 10,000 years.

Lazzaro Spallanzani (1729-1799) investigated salamander regeneration by amputating salamander tails and limbs. In 1864, 34 living axolotls were brought from Mexico to Paris. In 1867, Auguste Duméril, a French herpetologist at the natural history museum in Paris, published the first scientific papers on regeneration in the Mexican axolotl. The word axolotl comes from Nahuatl, a language of the Aztecs. The first living axolotls that came to Europe in 1864 were the founder generation of a population of hundreds of thousands of axolotls bred in laboratories and zoos. Most axolotls in research labs around the world are descendants of the group brought to Paris in the 1860s. The axolotl is easy to breed in the laboratory and is the most commonly used salamander model organism in regeneration research. The population in labs is often very inbred, so it has little genetic diversity.

An axolotl can regrow a lost leg in a few weeks to months. Within hours after an amputation, a wound epithelium covers the severed edge of the limb. After an injury, a mass of cells called a blastema forms and can regrow the missing part. Within days, the wound epithelium becomes innervated, which means it gets a nerve supply, and turns into a signaling center called the apical epithelial cap. Blastema formation requires an adequate nerve supply. Blastema cells with positional information interact with each other and with stump cells so that regenerated tissues reform in the right place. As of November 2026, a 2025 study suggests that a particular enzyme and gene work with retinoic acid to grow the right body part in the right spot. When an axolotl regrows a leg, every tissue is replaced, including skin, bone, cartilage and muscle.

When immune cells called macrophages were removed, salamanders lost their ability to grow back a limb. They formed scar tissue instead. Wound healing in a mammal leads to formation of scar tissue and does not progress to a blastema. Axolotls heal wounds without forming scar tissue, and wound healing eventually restores normal skin architecture. Scarring prevents tissue from growing back. So finding out how and why axolotls do not scar could unlock human tissue regeneration. Genes that direct the growth of organs and limbs during development are silenced in adult people. In axolotls they may be activated again after an injury. A tiger salamander grows a limb back in 155 to 180 days, while a juvenile axolotl takes approximately 40 to 50 days to do the same.

Wild axolotls are mostly dark in color. In the wild, an axolotl hides in mud and plants during the day and is active at night. It can reach about 12 inches long. It eats worms, insect larvae and small fish. It catches food by sucking it in. It communicates visually and chemically, and it can sense electrical impulses in the water to locate prey. A female axolotl lays her eggs on plants or rocks. The eggs hatch after about two weeks. Young axolotls get no parental care. Wild axolotls live 10 to 15 years. Salamanders live from 3 to 55 years depending on the species, and the axolotl is on the shorter side of that range.

Axolotls come from lakes and wetlands in southern Mexico City, in Mexico. They once lived in a series of lakes in the Mexican Central Valley, and many of the lakes where axolotls lived have been drained to reduce flooding. As of November 2026, the IUCN Red List lists the axolotl as Critically Endangered. An IUCN assessment found only 50 to 1,000 axolotls left in the wild, and the number of wild axolotls is decreasing. Urbanization and pollution of their lakes are the biggest threats to axolotls. Fish put into the waterways, such as tilapia and carp, compete with axolotls for food and eat their young. In 2025, scientists released 18 captive-bred axolotls into artificial wetlands near Mexico City. Farmers are increasingly using traditional farming methods, free of pesticides and fertilizers, to help conserve axolotls.

Words to know

• neotenic: keeping young traits
• blastema: mass of cells
• macrophages: immune cells
• epithelium: covering layer
• inbred: closely related