HideShark list
Every animal repairs wounds, but a few can rebuild whole body parts — legs, tails, eyes, jaws, even sections of the brain and heart — from scratch. The champions are salamanders and certain invertebrates, and understanding how they do it is a major goal of regenerative medicine.
Regrows limbs, jaws, spinal cord, and heart tissue
The gold standard for vertebrate regeneration. An axolotl regrows a complete limb — bone, muscle, nerves, blood vessels — in weeks, with no scar, and can repair its spinal cord, retina, jaw, and parts of its heart and brain. It does this throughout its life, and can regenerate the same limb repeatedly.
Full axolotl guide →Regrows limbs even at a crawl-speed metabolism
This blind cave salamander regenerates lost legs and tail like its relatives, remarkable given how slowly everything else about its body works. It is being studied for how regeneration proceeds at very low metabolic rates.
Full olm guide →Regrows limbs, toes, and tail at giant size
The salamander superpower scaled up to 1.5 metres. Giant salamanders regenerate damaged limbs and digits, and their ancient lineage makes them a key comparison point in regeneration research.
Full japanese giant salamander guide →Regrows limbs, tail, and lens of the eye
Newts regenerate legs and tails and are famous for rebuilding the lens of the eye from cells of the iris — a trick even the axolotl cannot match — and can do it dozens of times.
Full eastern newt guide →Regrows toes, feet, and limb segments
North America’s giant salamander regenerates damaged limbs and digits, an ability shared across the salamander family and part of why they are central to regeneration research.
Full hellbender guide →Regrows limbs, tail, and jaw
A close relative of the axolotl, the tiger salamander shares the salamander superpower of rebuilding whole limbs from a wound with no scar — and some populations stay in the aquatic larval form for life.
Full tiger salamander guide →Regrows a (different-looking) tail
Many lizards drop their tail to escape a predator and regrow it, but the new tail is supported by a rod of cartilage instead of vertebrae, so it is smoother and blunter. Geckos are studied because they are the closest relatives of mammals that can regrow an appendage.
Full leopard gecko guide →Regrows arms — and, in some, a whole body from one arm
A starfish routinely regrows a lost arm over months. In several species, a single severed arm containing part of the central disc can regenerate an entire new animal, a process called "comet" regeneration.
A new worm from almost any fragment
Cut a planarian into pieces and each piece can grow into a complete worm, head and all, within a week or two — thanks to a large reserve of adult stem cells called neoblasts. It is the most extreme whole-body regenerator among animals commonly studied.
Effectively does not age; rebuilds from tissue fragments
This tiny freshwater relative of jellyfish and corals is made largely of stem cells and continually renews its entire body. A small piece of hydra tissue can reorganise into a whole animal, and hydra show almost no increase in death rate with age.
Repairs its own heart — unlike its river cousins
Surface populations of this fish scar over heart damage like a human; some cave populations of the same species fully regenerate heart muscle. Comparing the two is helping pinpoint the genes that switch heart regeneration on and off.
Regrow a metre of bone every year
Antlers are the fastest-growing bone in any mammal — a bull moose regrows its entire rack, up to 20 kg, every summer after shedding it in winter. It is the only case of complete, repeated organ regeneration in a mammal, and the growth is driven by a pool of stem cells at the antler base.
Full deer and moose (antlers) guide →Among vertebrates, the axolotl — it regrows limbs, tail, spinal cord, jaws, and parts of the eye, heart, and brain, perfectly and repeatedly. Among invertebrates, planarian flatworms and hydra are more extreme still, able to rebuild an entire body from a small fragment.
We can regenerate the liver, skin, blood, and the very tips of fingers in young children, but not whole limbs. The leading explanation is that mammals trade regeneration for fast, robust wound-healing — we seal injuries quickly with scar tissue to prevent infection and blood loss, and that scarring blocks the slower, more delicate process of rebuilding. Salamanders form a special wound covering and a mass of reset cells (a "blastema") instead of a scar.
No. A regrown lizard tail is functional but not identical — it has a cartilage tube instead of separate vertebrae, different scale and colour patterns, and often no ability to be dropped again at the same spot. Regrowing it also costs the lizard fat reserves and can lower its social status.