Axolotl

The axolotl is a large salamander native only to a small number of lakes and canals around Mexico City, most famously Lake Xochimilco, unusual among amphibians for typically retaining its larval, fully aquatic form throughout its life rather than metamorphosing into a land-dwelling adult, a trait called neoteny that leaves it with feathery external gills and a finned tail into maturity. It is widely studied by scientists for its extraordinary regenerative ability, capable of regrowing entire lost limbs, portions of its spinal cord, and even parts of its heart and brain without scarring. Axolotls are opportunistic predators of small aquatic animals, and although they remain common in captivity worldwide and are popular in the pet trade, wild populations have collapsed due to habitat degradation, water pollution and introduced predatory fish, leaving the species classified as critically endangered in the wild.