Axolotl (Ambystoma mexicanum)

Axolotl (Ambystoma mexicanum), often called the "Mexican walking fish," is one of nature's most bizarre creatures. This permanently aquatic salamander retains its larval features throughout life, including external gills and a tadpole-like tail. Native to Lake Xochimilco in Mexico, it possesses extraordinary regenerative abilities—able to regrow limbs, spinal cords, even parts of its heart and brain. Unlike other amphibians, axolotls never undergo complete metamorphosis. Their unique "smiling" appearance and rare neoteny make them popular in scientific research and the pet trade. Sadly, this critically endangered species faces extinction in the wild due to habitat loss and pollution.