A starfish can regrow a lost arm over time, and some species regrow a whole body.

The longer version

Echinoderms run much of their body plan on decentralised systems rather than a single control centre. A starfish has no brain; instead a nerve ring and radial nerves coordinate the tube feet, and internal organs extend down into each arm.

When an arm is lost, cells at the wound site reorganise and begin rebuilding tissue in a process that can take many months. Because so much of the animal's basic machinery is repeated along each ray, some species can regenerate an entire body from a single severed limb plus a small piece of the central disc. The result is an animal that treats serious injury as a repairable event rather than a fatal one.

Where this entry sits

This collection gathers small surprises about mammals, reptiles, amphibians, birds, fish, insects, and the pets living alongside people. Expect odd details about senses, anatomy, and everyday behaviour that many people never notice in the animals around them. The full list sits on the Animals page, where every entry is listed in order.