Twelve axolotl facts, fact-checked
The axolotl (Ambystoma mexicanum) is a salamander that never grows up, and one of the most studied animals in regenerative medicine. Full profile in our axolotl guide.
1. They regenerate almost everything
Limbs, tail, spinal cord, heart tissue and parts of the brain regrow — without scarring.
2. They never metamorphose
Neoteny keeps them in larval form for life, retaining feathery external gills and staying aquatic.
3. They can be forced to metamorphose
An iodine or thyroid hormone dose triggers the change into a land-dwelling salamander, but shortens lifespan. It is not done in responsible keeping.
4. Their genome is huge
Around ten times the size of the human genome, which made sequencing it a significant technical achievement.
5. Wild numbers are tiny
Surveys of Lake Xochimilco have found extremely low densities, and the wild population is Critically Endangered.
6. Captive numbers are enormous
Thousands live in labs and aquariums worldwide — an animal simultaneously abundant and nearly extinct.
7. Captive stock is not a rescue population
Long-inbred laboratory and pet lines have low genetic diversity and are poorly suited to reintroduction.
8. The name comes from Nahuatl
Linked to Xolotl, an Aztec deity said to have transformed into a salamander.
9. Gills are feathery for a reason
Large external surface area extracts oxygen from still, warm, low-oxygen water.
10. They are cannibalistic as larvae
Young axolotls bite each other's limbs, which regenerate — likely a driver of the regenerative ability itself.
11. They resist cancer
Axolotls develop tumours far less readily than mammals, which is of considerable research interest given how much cell regrowth they do.
12. Their lake is the whole problem
Urbanisation, water extraction, pollution and introduced tilapia and carp have degraded Xochimilco. Restoring the canals is the only route to a wild future.
Read the full axolotl wildlife guide for IUCN status, population context and sources — or donate to WARN to help fund the partner teams protecting wildlife on the ground.
