The fish of the week is the axolotl (Ambystoma Mexicanum).
Axolotls once inhabited the freshwater canals of Mexico, particularly lakes Xochimilco and Chalco. Now, they're extinct in the wild, with the last alleged sighting being in 2019.
These mole salamanders never grow up; they're neotenic so they remain in their larval, aquatic state throughout their lives. The exception to this is an interesting gene that forces metamorphosis.
They can be found in a variety of morphs (colors), including Leucistic, Melanoid, Copper, and Green Fluorescent Protein! Axolotls grow up to 12" long, and in captivity require 30+ gallons of water per axolotl.
Axolotls have gill stalks covered in soft filaments, legs with 4 or 5 toes, and a long, muscular tail. They also boast a fascinating ability to regenerate body parts, even entire limbs!