Axolotls

 

Axolotls (Ambystoma mexicanum)

Image courtesy Wikimedia Commons

On holiday recently, a ten-year-old girl found an axolotl under a bridge over the River Ogmore in Bridgend. Experts said that the axolotl would have died if she had not rescued it, either as a tasty morsel, or because of conditions to which it was not suited. It is possible, though not proven, that this specimen was an unfortunate pet that had outgrown its fascination for its owner. Such is the fate of many creatures.

Axolotls are found in the wild only in the lakes of the Mexican Central Valley. They are a critically endangered species.  They are named after Xolotl, the Aztec god of fire and lightning. The legend holds that he turned himself into an axolotl to avoid sacrifice by other gods. Axolotls are an important feature in Mexican culture, appearing in murals and on bank notes.

They are bred in captivity for research purposes, because they have an extraordinary ability to regenerate parts of their bodies, including limbs, and parts of their eyes, brains, and hearts.

They are neotenic, meaning that they reach maturity without metamorphosing from a fully aquatic form to an amphibious being, as salamanders or tadpoles do. Consequently, they retain their feathery gills and live their entire lives in water.

            They can be triggered into metamorphosis in laboratory conditions through an injection of iodine or thyroxine. Following that, the gills and fins are resorbed, while lungs develop, and eyelids grow, allowing them to adapt to life on land. They then resemble salamanders, though differences are visible. For example, a metamorphosed axolotl’s toes are longer than a salamander’s!

Wild axolotls are carnivorous, preying on small fish, worms, molluscs and other aquatic beasts. They are attracted to food by smell, and suck it into their stomachs. They have teeth, but they are vestigial and serve no practical purpose. The average lifespan of a wild axolotl is five years, though some manage to survive for ten. In captivity, they typically live between ten and fifteen years, though exceptionally, some can reach twenty years.

Axolotls become sexually mature between eighteen and twenty-four months, and reproduce through external fertilisation. The average length of a mature axolotl is 23 cms (9 inches) though there is some variation.

Concern about the axolotl’s decline has led to attempts to release captive-bred individuals, but the very real fear is that they will suffer the same fate as wild-bred animals. Pollution, the introduction of non-native predators, and greater urbanisation, all threaten the future of these fascinating creatures.

Image courtesy Wikimedia Commons