The axolotl (Ambystoma mexicanum) is a paedomorphic salamander. It is unusual among amphibians in that it reaches adulthood without undergoing metamorphosis. Instead of taking to the land, adults remain aquatic and gilled. The species was originally found in several lakes underlying what is now Mexico City, such as Lake Xochimilco and Lake Chalco.

Axolotls have four pigmentation genes; when mutated, they create different color variants. The normal wild-type animal is brown or tan with gold speckles and an olive undertone. The five most common mutant colors are listed below.

1. Leucistic: pale pink with black eyes.
2. Xanthic: grey, with black eyes.
3. Albino: pale pink or white, with red eyes, which is more common in axolotls than other species.
4. Melanoid: all black or dark blue with no gold speckling or olive tone