Axolotl (Ambystoma mexicanum)

Axolotls are fully aquatic salamanders that live in the lakes of Mexico. Unlike most other salamanders, axolotls never undergo metamorphosis; rather, they reach adulthood while retaining typical juvenile characteristics like external gills. Oddly enough, metamorphosis is still in their genetic code and can be induced with an injection of iodine. This changes an axolotl’s body to be much like that of an adult tiger salamander. This induced adult form can live on land, but it is never found in the wild. Axolotls are also only active at night and are very sensitive to light.