Head to head
Giant Salamander vs Axolotl
Giant salamanders and axolotls are both salamanders, both fully aquatic, and both stars of the amphibian world, so they often get mixed up. But they are in different families, differ enormously in size, and take opposite approaches to growing up.
| Giant Salamander | Axolotl | |
|---|---|---|
| Family | Cryptobranchidae | Ambystomatidae (mole salamanders) |
| Adult size | Up to 1.5 to 1.8 m | About 20 to 30 cm |
| Metamorphosis | Yes, loses gills as an adult | No, stays in larval form (neoteny) |
| Gills as an adult | None, breathes through skin folds | Keeps feathery external gills |
| Native range | China, Japan, eastern USA | Lakes and canals near Mexico City |
| Habitat | Cold, fast, rocky streams | Cool still and slow fresh water |
| Regeneration | Yes | Yes, and heavily studied |
| Wild status | Chinese species Critically Endangered | Critically Endangered in the wild |
Giant Salamander vs Axolotl: common questions
Is an axolotl a type of giant salamander?
No. They are both salamanders but in different families. The axolotl is a mole salamander, family Ambystomatidae, closely related to the tiger salamander, and it is a small animal by salamander standards. Giant salamanders are the family Cryptobranchidae, a separate and very ancient lineage that includes the hellbender of North America and the giant salamanders of China and Japan. The two are confused because both live permanently in water and both look primitive, but an adult Chinese giant salamander can be fifty times the length of an axolotl and has no external gills.
Why does the axolotl keep its gills when other salamanders lose theirs?
The axolotl has largely switched off the hormonal signal that normally drives metamorphosis. In most salamanders a surge of thyroid hormone late in larval life triggers the change to a land-living adult, but in the axolotl the thyroid system is much less responsive, so the animal simply continues growing in its larval form and becomes sexually mature that way. This is thought to be an adaptation to a stable, permanent body of water where there was little advantage to moving onto harsh, dry land. If an axolotl is given thyroid hormone artificially it will metamorphose into a land salamander, though this shortens its life.
Which is more endangered?
Both are Critically Endangered in the wild, but their situations differ. The Chinese giant salamanders have collapsed by an estimated 80 per cent or more and may be functionally extinct across much of their range, hunted for luxury food and swamped by farm escapes, with recent surveys of many sites finding almost no wild animals. The axolotl survives in the wild only in a small remnant of the Xochimilco canal system near Mexico City, with wild numbers estimated in the hundreds or low thousands and falling, threatened by pollution and introduced fish. The axolotl is in no danger as a species overall, though, because hundreds of thousands live in laboratories and home aquariums.