Physiology
The Axolotl is unusual in nature because it retains its larval form into adulthood. In fact, it becomes sexually mature in this state. This adaptation, known as neoteny, is often viewed as a backward step in evolution because it prevents the axolotl from living on land, and as a result it can't colonise new habitats. However, it has led to the axolotl being quite successful in its native habitat, at least until the arrival of man.
The Axolotl is carnivorous and has reasonably typical internal carnivore anatomy, with the main exception of the teeth. Its teeth are pedicalate (i.e. they're small stumps, like cones). With these it grips its food, manoeuvering it into position before swallowing it whole. It has a three-chambered amphibian heart (unlike the mammalian four-chambered heart), and, like all amphibians, it is poikilothermic (its body temperature is dependent on its surroundings). One thing to note is that although they retain larval morphology, they do develop rudimentary lungs, and axolotls can be seen to occasionally rise to the surface, take a quick gulp of air to fill these lungs, and then quickly descend to the bottom once more. From my observations, I think that the lungs develop shortly after the rear legs reach their full length.
Axolotls are famous for their fabulous regenerative abilities. Regeneration studies carried out around the world often involve the Axolotl. For example, a young axolotl that loses a foot to a sibling will usually grow it back over a period of a few weeks. This regeneration occurs via the formation of a "bud" at the end of the damaged appendage followed by growth of the new foot. Entire limbs can be regenerated and even portions of the brain and spine.
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