A species
Axolotl
Ambystoma mexicanum
A salamander that never grows up and regrows lost legs.
You and the axolotl last shared an ancestor about 350 million years ago (on 1 December, if life's history were one year).
Meet a salamander that never grows up and can regrow its own legs. The axolotl is a relative of frogs, like the red-eyed tree frog beside it on the tree, but it stays in water for its whole life. It keeps its soft, feathery gills and paddle-like tail, even though it also grows working lungs, and it can lay eggs that hatch while still looking like a young one itself.
If it loses a leg, it grows a new one. Within weeks it can build a near-perfect leg, with bones, muscles and nerves in the right places and no scar. It can also regrow parts of its heart and brain, which is one reason scientists study it.
In the wild it lives only in cool, muddy water near Mexico City, now just in the leftover canals of one lake. Wild axolotls are dark, mottled brown and green to hide in mud. Very few are left, because of dirty water, loss of home, new suburbs and hungry introduced fish. An adult is about as long as a school ruler.
Huge DNA
Its DNA holds about 32 billion letters, more than ten times as much DNA as a person has. When scientists first read it all, it was the largest set of DNA ever fully read.
A trip to Paris
In 1864, 34 live axolotls were taken from Mexico to Paris. Most pet and lab axolotls come from that group, and today's pale pink and white pets trace back to one white male among them.
A god in hiding
Aztec legend says the god Xolotl turned himself into a salamander to avoid being sacrificed. That story gave the axolotl part of its name.