The axolotl, a unique aquatic salamander, is known for its distinctive appearance, often described as having a “baby-like” face and feathery external gills. Its slender body and lizard-like limbs contribute to its unique look. This creature maintains a fully aquatic lifestyle throughout its life, prompting many to question its biological classification. A common inquiry is whether this intriguing animal is a reptile or something else entirely.
Axolotls Are Amphibians
Despite common misconceptions and their somewhat reptilian appearance, axolotls are unequivocally amphibians. They belong to the class Amphibia, which includes frogs, toads, and other salamanders. The axolotl’s scientific classification places it within the Order Caudata, firmly establishing them as a type of tailed amphibian or salamander, distinguishing them from reptiles.
Defining Amphibians
Amphibians are ectothermic vertebrates, meaning their body temperature is regulated by their external environment. A defining characteristic of most amphibians is their “dual life” cycle, often involving an aquatic larval stage with gills that transitions to a more terrestrial adult stage with lungs. Their skin is typically moist, smooth, and permeable. Many amphibians also possess glands in their skin that produce mucus, keeping the skin moist. Reproduction generally occurs in water, with amphibians laying soft, jelly-like eggs that lack a hard shell.
Amphibians Versus Reptiles
The distinctions between amphibians and reptiles are fundamental. Reptiles, which include snakes, lizards, and turtles, possess dry, scaly skin that helps prevent water loss, allowing them to thrive in more arid environments. In contrast, amphibians have moist, permeable skin, making them susceptible to dehydration and often tying them to aquatic or damp habitats. A key difference also lies in their reproductive strategies. Amphibians typically lay gelatinous eggs in water, and their young undergo metamorphosis. Reptiles, however, lay amniotic eggs with leathery or hard shells on land, and their hatchlings emerge as miniature versions of the adults. While reptiles breathe solely through lungs, amphibians may use gills, lungs, and their skin for respiration throughout their life stages.
Axolotl’s Unique Biology
Axolotls possess several biological traits that set them apart, even within the amphibian class, and can contribute to confusion about their classification. The most notable is neoteny, where they retain larval characteristics into adulthood. This means axolotls remain fully aquatic throughout their lives, maintaining their feathery external gills and a caudal fin, rather than undergoing metamorphosis to a terrestrial form. Despite developing functional lungs, they primarily rely on these external gills for breathing underwater, a retention of juvenile features that makes them appear distinct from typical adult amphibians. Additionally, axolotls are recognized for their remarkable regenerative abilities, capable of regrowing limbs, lungs, hearts, jaws, spines, and even parts of their brains.