The amphibian known for its ability to regenerate lost limbs is the axolotl. This Mexican salamander can regrow entire limbs, including bones, muscles, nerves, blood vessels, and skin, rather than simply healing an injury with scar tissue.
Axolotls are especially valuable to regeneration researchers because their bodies can rebuild complex structures in the correct shape and position. After an injury, cells near the wound form a mass called a blastema, which provides the growing tissue used to reconstruct the missing limb. Axolotls can also regenerate parts of the tail and repair certain tissues in the heart, eyes, and nervous system.
The axolotl is a salamander, not a frog or toad, and it famously retains juvenile features such as external feathery gills throughout adulthood. Its regenerative ability becomes weaker after metamorphosis and can decline with age, but it remains unusually strong compared with that of most adult vertebrates. Newts also regenerate limbs, but the axolotl is the classic quiz and laboratory example.