Animals That Can Regrow Lost Body Parts

An axolotl can rebuild a lost limb as an adult. The replacement includes multiple kinds of tissue, such as skin and muscles, as well as a new skeleton and digits. That makes the axolotl a good starting point for understanding what it means to replace a whole structure.

A green anole can grow a new tail after shedding the old one. The replacement has a tube of cartilage where the old tail had separate vertebrae. The pattern of muscles changes too, giving you an example of regrowth that restores a body part with a different internal design.

An arm shed by this spotted sea star can grow into a separate animal. In between, it looks something like a comet. The original arm is the long tail, with a tiny central disk and much shorter new arms growing at one end. This ability is documented for particular sea stars, including this Indo-Pacific species.

A Cairo spiny mouse can restore the missing tissue around a wound in its outer ear. Researchers found that the regrown area included cartilage, skin, and hair follicles. That’s an unusual degree of repair in a mammal, where a closed wound can still leave a scar instead of replacing the original structures.

The zebrafish can replace lost heart muscle after a partial injury. In one study, it restored the missing part of a ventricle, one of the heart’s chambers. Existing heart muscle cells supplied new ones, a different feat from the external repairs seen in axolotls and lizards.

A surviving piece of this flatworm can regrow a head or a tail, depending on what is missing. A fragment from the middle can grow both ends. The worm has stem cells that supply many of the different cell types needed to rebuild those parts.

This freshwater animal has a mouth surrounded by tentacles at one end and a foot that anchors it at the other. When the head is lost, Hydra can rebuild the tentacled end from its surviving body column. The new head brings back the mouth as well as the ring of tentacles.

This sea cucumber can rebuild its intestine after expelling internal organs. The replacement includes the intestine’s own network of nerves. That means more has to grow back than the walls of the digestive tube.

An American lobster can replace a lost claw or walking leg. It can even release a limb to escape a threat. Regrowth extends past those big, easy-to-spot claws. A lobster can also replace an antenna.

An adult eastern newt can replace a lost lens inside its eye. The new lens grows from tissue in the iris. Researchers comparing the lenses found that many of the new lens’s proteins had the same properties as their counterparts in the original.

The starlet sea anemone can rebuild its feeding end. In juveniles, researchers watched a new mouth take shape, the muscular throat reform, and new tentacles lengthen. The little tentacle crown is the visible part of a repair that also restores structures inside the animal.

In a 2021 report, some individuals of this sea slug regrew a body from the separated head. This is an extreme version of regrowth after shedding a body part. The result came from particular observed animals, and it offers a very different comparison with a lizard replacing a tail.

A red deer stag sheds and replaces its antlers each year. The new antlers grow beneath a soft covering called velvet, which the stag sheds when the antlers are fully grown. For a red deer, regrowth is part of the ordinary seasonal cycle.