Credit: Pixabay, CC-0 Axolotls (Ambystoma mexicanum) are a critically endangered species of salamander. The species has only one natural habitat remaining, a series of canals in Mexico City, and only 50 to 1,000 axolotls are estimated to be left living there. However, axolotls have become popular both as pets and as model organisms in research, so descendants of axolotls collected from Mexico City many years ago can now be found around the world. Axolotls are highly regenera...