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axolotl(ăk`səlŏt'əl), a salamandersalamander,
an amphibian of the order Urodela, or Caudata. Salamanders have tails and small, weak limbs; superficially they resemble the unrelated lizards (which are reptiles), but they are easily distinguished by their lack of scales and claws, and by their moist, usually
..... Click the link for more information. , Ambystoma mexicanum, found in certain lakes in the region of Mexico City, which reaches reproductive maturity without losing its larval characteristics. This phenomenon is called neotenyneoteny
, in biology, sexual maturity reached in the larval stage of some animals. Certain environmental conditions can inhibit the completion of metamorphosis; low temperature or lack of available iodine retard the action of the thyroid gland, the larval form may mature
..... Click the link for more information. ; in salamanders it is apparently caused by certain environmental conditions, particularly a low level of iodine in the water, which affects the functioning of the thyroid gland. The axolotl grows larger than ordinary larval salamanders and develops sexually, but it retains bushy external gills and a well-developed tail. It also has a broad head and stubby legs; its skin is a black-speckled dark brown. Permanently aquatic, never undergoing metamorphosis to a terrestrial form characteristic of amphibiansamphibian,
in zoology, cold-blooded vertebrate animal of the class Amphibia. There are three living orders of amphibians: the frogs and toads (order Anura, or Salientia), the salamanders and newts (order Urodela, or Caudata), and the caecilians, or limbless amphibians (order
..... Click the link for more information. , it may grow as long as 13 in. (33 cm). It is also known as the Mexican walking fish because of its appearance.
The axolotl was not recognized as a salamander until 1865, when several specimens at the Jardin des Plantes in Paris suddenly underwent metamorphosis. After some experimentation it was discovered that when their pools were dried up most of the animals changed into the adult form. Axolotls will also mature normally if fed thyroid gland extract. The related North American tiger salamander, A. tigrinum, often exhibits neoteny in the Rocky Mts., where the iodine content of the water is low. Since the late 1990s the axolotl has become increasingly endangered in its natural habitat due to pollution and competition from introduced fish.
The axolotl is classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
..... Click the link for more information. , subphylum Vertebrata, class Amphibia, order Urodela, family Ambystomidae.