“Axolotls can fully regenerate a lost limb—complete with bone, muscle, and nerves—within weeks.”
The axolotl is a Mexican salamander that keeps its larval form for life, retaining feathery external gills and living fully underwater. Able to regrow limbs, spinal cord, and even parts of its brain, it is Critically Endangered in the wild.
By An Nguyen · Published · Updated
Ambystoma mexicanumUrodelaAmbystomatidae
Browse axolotl photographs—from feathery gills and color variants to the canals of Lake Xochimilco.
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Core article
A closer look at habitat, diet, behavior, reproduction, and conservation.
The axolotl (Ambystoma mexicanum) is a salamander that never grows up. Instead of transforming into a land animal like other salamanders, it stays in its gilled, aquatic larval form for life — and it can regrow lost body parts so completely that it has become one of the most-studied animals in regenerative biology. Yet the wild axolotl survives in only one place on Earth, the canals of Xochimilco in Mexico City, where it is critically endangered even as millions live in labs and home aquariums.
Two traits set the axolotl apart. The first is neoteny: it reaches breeding age while keeping its larval body. Most salamanders metamorphose from water-dwelling, gilled larvae into lung-breathing land adults, but the axolotl's body does not trigger that change (it lacks the usual surge of thyroid hormone), so it keeps its feathery external gills and finned tail and stays in the water its whole life.
The second is regeneration. When an axolotl loses a limb it does not simply scar over — cells at the wound revert to a stem-like state, form a mass called a blastema, and rebuild the limb over weeks with correct bone, muscle, blood vessels, and nerves. Axolotls can also regenerate parts of the spinal cord, heart, and even brain, which is why laboratories worldwide keep them.
Adults usually reach 6 to 12 inches (rarely up to 18) and weigh a few ounces, with soft, somewhat gelatinous bodies and four slender legs. The signature feature is the three pairs of feathery external gills behind the head; packed with blood vessels, they look deep red and wave to draw oxygen from still water, though the axolotl also has simple lungs and gulps air at the surface. Its scaleless skin is highly permeable — which makes it very sensitive to water quality — and a lateral-line system along the body senses tiny movements in the water. Wild axolotls are dark and mottled for camouflage; captive breeding has produced many colour morphs, most famously the pale, dark-eyed leucistic form.
Wild axolotls have one of the smallest ranges of any vertebrate. They once lived in the linked highland lakes of Xochimilco and Chalco in the Valley of Mexico, but Chalco was drained to stop flooding, and today the only wild population clings to a degraded network of canals and wetlands in the Xochimilco district of southern Mexico City. It is a bottom-dweller in shallow, cool, slow freshwater thick with plants. A closer look at that habitat is in where wild axolotls live and how Xochimilco's chinampa refuges work.
The axolotl is a carnivore near the top of its small food web, eating aquatic worms, insect larvae (especially chironomids), small crustaceans, molluscs, and fish fry. With no chewing teeth, it feeds by suction: when its lateral line detects prey nearby, it holds still until the target is close, then snaps open its mouth and drops the floor of the throat, creating a vacuum that pulls prey and water straight in within a fraction of a second.
Axolotls are largely solitary and most active in low light, spending the day buried in mud or hidden in vegetation away from herons and other predators. They move mostly by walking along the bottom on their legs, saving their finned tail for short bursts of swimming when startled. Outside the breeding season they show little social behavior.
Breeding is entirely aquatic. A male deposits cone-shaped sperm packets (spermatophores) on the bottom, and the female takes one into her cloaca to fertilise her eggs internally. She then lays a large clutch — 100 to 1,000 eggs — attaching them one by one to submerged plants, where they hatch into tiny larvae in about 10 to 14 days. Because of neoteny there is no metamorphosis; the young simply grow, reaching maturity in their aquatic form at about one to two years. Wild axolotls live an estimated 10 to 15 years.
The wild axolotl is Critically Endangered, with recent surveys suggesting fewer than 1,000 — possibly as few as 50 — remain. The causes are all human: Mexico City's growth swallowed the old lakes, and the surviving Xochimilco canals carry sewage, industrial runoff, and pesticides that pass easily through the axolotl's permeable skin. Non-native tilapia and carp, introduced in the 1970s, eat its food, eggs, and young.
The paradox is that millions of axolotls live in labs and the pet trade, but those animals are inbred and genetically distinct from the wild lineage, so they are not a substitute for the wild population. Conservation focuses on breeding wild-type genetics, building filtered "refuge" canals in Xochimilco, and encouraging pesticide-free farming to restore water quality.
Kingdom
Animalia
Phylum
Chordata
Class
Amphibia
Order
Urodela
Family
Ambystomatidae
Genus
Ambystoma
Species
A. mexicanum
Axolotls can fully regenerate a lost limb—complete with bone, muscle, and nerves—within weeks.
Unlike most amphibians, axolotls never metamorphose; they keep their external gills and aquatic lifestyle for their entire lives.
Axolotls can also regenerate heart tissue and portions of their brain, making them invaluable to medical research.
The name 'axolotl' comes from Nahuatl, the Aztec language, and roughly means 'water monster' or 'water servant of Xolotl,' the dog-headed Aztec god.
Wild axolotls are found only in the canal system of Lake Xochimilco within Mexico City—one of the most restricted ranges of any vertebrate.
Axolotls can be leucistic (pale pink with dark eyes), melanoid (all black), or wild-type (dark with golden speckles), and many color variants exist in captivity.
Select a question to reveal the answer.
An axolotl is a type of salamander native to Mexico. Unlike most amphibians, it keeps its larval features—including external gills—for its entire life instead of undergoing metamorphosis.
Yes. Axolotls can regrow a fully functional limb, including bones, muscles, blood vessels, and nerves, within weeks. They can also regenerate heart tissue and parts of their brain.
Wild axolotls are found only in the canals and remnant lake areas of Lake Xochimilco in Mexico City. This tiny habitat makes them one of the world's rarest vertebrates.
Axolotls are carnivores. They eat worms, insect larvae, small fish, crustaceans, and mollusks. They hunt using suction, rapidly opening their mouths to draw prey in.
No. Axolotls are amphibians—closely related to salamanders and newts—not fish. They are sometimes called 'Mexican walking fish' because of their legs, but they are not fish.
Axolotls exhibit neoteny—they become sexually mature while retaining larval characteristics. They produce hormones that suppress metamorphosis, keeping them aquatic their whole lives.
Yes. Axolotls are Critically Endangered in the wild. Pollution, habitat loss, invasive fish species, and water drainage from Lake Xochimilco have pushed wild populations to very low numbers.
Most axolotls reach 6 to 12 inches (15–30 cm), though some grow up to 18 inches (45 cm). Wild individuals tend to be slightly smaller than those kept in captivity.
Yes. Axolotls are popular in captivity and are bred in large numbers. Captive populations are genetically distinct from the wild ones, which are still critically endangered.
Axolotls typically live 10 to 15 years both in the wild and in captivity. Good water quality and diet are key to a long, healthy life.
Neoteny is the retention of juvenile or larval features into adulthood. Axolotls are a classic example—they keep their external gills and aquatic lifestyle even when fully grown and sexually mature.
Axolotls' extraordinary regeneration ability makes them one of the most studied animals in biology. Scientists study them to learn how tissues and organs might one day be regenerated in humans.
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