Only a handful of creatures can regenerate body parts, making them something special in the animal kingdom.
From the carnivorous Mexican axolotl to the color-changing chameleon and the red-nosed reindeer, these five animals can regenerate everything from a pair of antlers to an entire body!
Axolotls
According to legend, the Mexican axolotl is the Aztec god of fire and lightning disguised as a salamander to escape sacrifice. Whether you believe that the story of this paedomorphic salamander has merit, there is no denying that this amphibian certainly has Godlike characteristics!
Many people know the axolotl for its ability to regenerate lost limbs or even its tail. What most people do not know, however, is that this creature can also replace its lower jaw, heart, and brain! After losing a body part, axolotl cells become less specialized and rearrange to reconstruct the missing body part.
The axolotl is a critically endangered species with great scientific value because of its regenerative ability, ability to change color to camouflage itself, and being the only legged salamander that remains aquatic for its entire life. More importantly, though, is its value to human medical research into wound repair and embryo development since the axolotl embryo is easily observable through various stages of growth.
Starfish
There are around 2,000 species of starfish worldwide, and each of them is capable of regenerating limbs. Some species, however, can regrow an entirely new body from just a part of a limb.
Like the axolotl, the starfish has cells that are able to alter their own structure. So, when a limb is lost, the skin or muscle cells can transform back into stem cells allowing them to become whatever they need to be to promote regeneration of the lost limb – or sometimes the torso!
Although not endangered like the axolotl, the starfish still plays a role in human medicine. Most notably, the sea star (scientists prefer this term as it is not actually a fish) has a non-stick material in its outer layer that has proven valuable in treating human inflammatory conditions and has proven invaluable in understanding stem cell generation.
Flatworm
The flatworm looks rather unremarkable, but this soft-bodied invertebrate is actually quite incredible. There are over 12,000 flatworm species, and each one can fully regenerate.
Like other regenerative creatures, the flatworm uses its own cells to regenerate lost tissue. In the flatworm, these cells are called neoblasts that behave similarly to stem cells. For example, when a flatworm gets cut in half, the pluripotent neoblast cells reactivate in the body and move to the wounded area, where they divide, creating new cells. These new cells then form new body parts, and through this cellular process, the flatworm can regenerate a whole new worm and duplicate itself infinitely.
Although small and lesser-known than other creatures, the flatworm plays a starring role in the study of stem cells because it has an unlimited number of pluripotent stem cells, whereas humans have very few, limiting our ability to study them in ourselves.
Salamanders
Salamanders are known for regenerating whole limbs, tissue, and even organs. As with other creatures on our list, the salamander regrows lost body parts through the use of its own cells. There are over seven hundred living salamander species, and each can regenerate body parts, but not all do so by the same method.
Most commonly, the salamander regenerates limbs when existing muscle cells break up and re-enter the cell cycle to create a new limb. This cell reprogramming is a similar regeneration approach to the starfish but a different approach to regeneration than the axolotl (another salamander species), which relies on stem cells rather than mature cells.
Like other creatures capable of regeneration, the salamander has a part to play in human medicine. In fact, researchers believe that the key to unlocking human tissue regeneration lies in the limb regeneration of the salamander.
Reindeer
Unlike other creatures on our list, the reindeer cannot regenerate limbs, but it does regenerate antlers each year. Unlike other deer species, the male and female reindeer grow antlers which attract mates but shed when hormones shift after mating or calving.
A reindeer’s antlers grow from bone and have a keratin sheath protecting them. A soft velvet layer develops over the antlers to provide a rich blood supply that fuels rapid growth. Over time, the velvet wears off, and the antlers eventually fall off. New antlers begin to grow when the pituitary gland releases specific sex hormones.
Like other regenerative animals, the reindeer plays a crucial part in human medicine. Scientists believe the reindeer’s ability to regenerate skin (velvet) annually at such an incredible growth rate holds value to human skin regeneration.
