Axolotl

The axolotl (Ambystoma mexicanum) is a salamander from Mexico that never grows up. It reaches adulthood while keeping its larval body, including the feathery external gills around its head, and spends its entire life underwater. It lives in the wild in only one place, the canals of Xochimilco in southern Mexico City, where it is Critically Endangered, even though millions live in tanks and laboratories around the world.

It is a salamander, not a fish. The axolotl is an amphibian in the genus Ambystoma, the mole salamanders, and its closest relative is the tiger salamander. The confusion comes from its nickname, Mexican walking fish, and from the fact that it keeps its gills and stays in the water for life instead of metamorphosing and moving onto land like almost every other salamander does.

No. There is no blue axolotl in nature or in captivity. The blue one comes from Minecraft, where it is the rarest variant, appearing with a chance of about one in 1,200, a figure the developers chose to reflect how few axolotls are left in the wild. Real axolotls come in wild brown, leucistic pink, white or golden albino, solid black melanoid and copper, and some laboratory lines glow green under ultraviolet light.

Most of them are not. The pale pink axolotl with black eyes that appears in almost every photo is a leucistic morph, an animal with very little pigment in its skin, so the blood vessels underneath show through. It is common in captivity and rare in the wild, where axolotls are dark brown or greenish grey speckled with gold, a color that keeps them hidden in the murky water of the Xochimilco canals.

Not from the wild. Nearly every axolotl kept as a pet or used in a laboratory descends from a shipment of roughly 34 animals that left Mexico for Paris in the 1860s and bred prolifically there. After more than 150 years of captive breeding, those lines have drifted genetically away from the wild population in Xochimilco, which is why biologists insist that the millions of axolotls in tanks do not make the species safe.

The axolotl is Critically Endangered due to the near total destruction of its natural habitat. Lake Xochimilco, the only place where wild axolotls exist, has shrunk dramatically as Mexico City expanded around it. Water pollution from urban runoff and wastewater has severely degraded the canals, while invasive fish such as carp, tilapia, and African cichlids prey on axolotl eggs and juveniles. Wild populations fell by more than 99% between 1998 and 2014, with current estimates placing only 50 to 1,000 individuals remaining.

Yes, and their regenerative abilities go far beyond limbs. Axolotls can fully regrow amputated legs, feet, and toes, including bone, muscle, nerves, and skin, with no scar tissue forming. They can also repair segments of the spinal cord after injury, recover damaged portions of the heart muscle, and restore parts of the brain. This process typically takes a few weeks for a limb. No other vertebrate is known to regenerate complex structures so completely, which is why axolotls are central to regenerative medicine research worldwide.

Wild axolotls exist only in the canal system of Lake Xochimilco, located on the southern edge of Mexico City at about 2,240 meters above sea level. Historically the species also inhabited nearby lakes Chalco, Texcoco, and Zumpango, but drainage projects and urban growth eliminated those habitats during the 20th century. Today the species survives in a small network of canals within the chinampas, the traditional floating garden system of Xochimilco, which is a UNESCO World Heritage Site.

Axolotls are carnivores that hunt by suction, drawing prey into their mouths with a rapid gulp. In the wild they feed on small invertebrates including worms, insect larvae, small crustaceans, and mollusks, as well as small fish when available. They have small, rudimentary teeth that are not used for chewing but help grip prey. In captivity they are typically fed bloodworms, brine shrimp, earthworms, and specially formulated pellets. They are ambush predators and tend to be most active at night.

In Nahuatl mythology, the axolotl was linked to Xólotl, the dog headed god associated with lightning, fire, and the underworld, who was believed to guide the souls of the dead through the underworld. According to legend, Xólotl transformed into an axolotl to escape being sacrificed along with the other gods during the creation of the sun and moon. The name axolotl comes from Classical Nahuatl and is generally interpreted as meaning 'water dog' or 'water monster.' The species was also eaten by the Mexica people as a food source.

Axolotls are kept as pets in many countries and can thrive in captivity with proper care, though they have specific requirements. They need cool water between 14 and 20 degrees Celsius, as higher temperatures cause stress and illness. They require a spacious aquarium with gentle filtration, no bright lighting, and hiding spots. They should not be housed with other fish. In Mexico, keeping axolotls as pets is regulated under wildlife protection laws. Elsewhere, ownership rules vary by country and region, so checking local regulations before acquiring one is important.