Click here: The Natural History and Captive Care of the Mexican Axolotl, Ambystoma mexicanum: Natural History – Part 1, to read the first part of this article.
Mexican axolotls feed upon shrimp, aquatic worms, copepods, insects and other invertebrates and small fish. Adults are major predators upon small axolotls and axolotl eggs. The larvae are largely carnivorous, but may consume some algae as well.
Their main predators are herons and other wading birds, fishes and larger axolotls.
Males deposit spermatophores (sperm-filled capsules) on the lake bottom from March through June. After nudging the cloacal region of a gravid female – and being nudged in return – the male undulates his tail in front of her, most likely releasing pheromones (chemical attractants) in the process. He then leads the female over the spermatophore, which is taken into her cloaca. Fertilization occurs internally. The eggs, 100-300 in number, are laid after a gestation period of 2 weeks. They are attached to aquatic vegetation and hatch in 10-14 days.
The young reach sexual maturity in approximately 18 months. The Mexican axolotl is a paedormorphic (or neotenic) salamander, meaning that it retains a number of larval characteristics, including external gills (adults have lungs as well) and an aquatic lifestyle. Animals injected with the thyroid gland hormone thyroxin will transform into terrestrial adults, but do not survive for long.
The Mexican axolotl is an ideal laboratory subject, and quite important in medical research. Studies of it have led to important advances many fields, including gene expression, neurobiology and limb/organ regeneration.
Axolotls possess a greater facility for regeneration than do most amphibians, and can re-grow limbs, digits, gills, tails and portions of the liver, spleen and eye. This ability may have important implications for people, and has been under investigation for some time.
Nearly all axolotls in captivity today can trace their origins to specimens collected from Lake Xochimilco and shipped to Paris in 1864. Three aquatic salamanders in the Genus Ambystoma have historically shared this species’ habitat, and it is believed that hybridization with these occurred at the time of that original collection. Current lab and pet populations may, therefore, differ genetically from wild axolotls.
The axolotl is closely related to the tiger salamander (A. tigrinum), and hybrids are fertile. Tiger salamanders also exist in neotenic form in certain populations. There is evidence that the animals forming the basis of today’s captive stock have interbred with neotenic tiger salamanders.
The name “axolotl” is taken from that of the Aztec god Xolotl, who was believed to have taken on the animal’s form, and loosely translates to terms such as “water dog”, water sprite”, “water slave” and “water monstrosity”.
We’ll take a look at captive care next time. Until then, please write in with your questions and comments. Thanks, Frank Indiviglio.
I have written articles about axolotl relatives as well. Please see:
The Spotted Salamander, Ambystoma maculatum – Part I and Part II
Algae and Salamander Eggs – an odd partnership
The abstract of an International Zoo Yearbook article detailing the use of the axolotl as a “flagship species” for the conservation of its habitat is posted at: