Edinburgh Zoo is home to two axolotls.
The axolotls can be found in our Wee Beasties exhibit.
The axolotl (Ambystoma mexicanum) is also known as a Mexican salamander or a Mexican walking fish. They are found only in the lake of Xochimilco, near Mexico City. The name “axolotl” is thought to have originated from the Aztec word “atl”, meaning water, and “xolotl”, meaning monster. And whilst they might not look very appetising, axolotls formed a staple part of the Aztec’s diet.
The axolotl has a long, slim, darkly coloured body, and short legs, with four digits on the front feet and five on the hind feet. The axolotl generally inactive during the day, choosing to rest on the substrate with the gills splayed. Occasionally they move slowly and may surface to take a breath of air. Young axolotl feed on algae, but adults will feed on aquatic invertebrates.
Axolotls exhibit an unusual and extreme trait known as neoteny. This means that Instead of metamorphosing like other amphibians and taking to land, this rare species remains gilled and prefers to live its whole life in water. One of their most defining characteristics is the branch-like gills which protrude from the neck on either side of the head. The gills are covered in feathery filaments which increase the surface area for gas exchange, this in spite of the fact that they also develop lungs, which are very rudimentary.
Axolotls become sexually mature between 12 and 18 months of age and males will ‘dance’ to initiate courtship, often nudging the female before depositing several cone-shaped packets of sperm known as spermatophores onto rocks and plants. These are taken up by the female, for internal fertilisation of her eggs. She lays the eggs 24 hours later, each one becoming enveloped in mucus as it emerges. They become glued to each other and to the substrate where they incubate for two to three weeks. A single female axolotl can produce as many as 400 eggs in a day.
Axolotl populations are diminishing at an alarming rate due to a number of factors, including increased urbanisation of Mexico which in turn leads to an increase in water pollution and the draining of their natural habitat. They have also been used extensively in scientific research because of their ability to regenerate limbs and are probably one of the most scientifically studied salamanders in the world.