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The Nature Nut

Rosamund Pojar

Last week I read about how axolotls can regenerate parts of their bodies that are amputated or die and appear to be able to halt the process of aging (called negligent senescence). Now scientists are studying how they do this. Since I know almost nothing about these interesting creatures I started doing some research.

Meanwhile, my eight-year-old granddaughter made a birthday card for her Grandad. Imagine my surprise when she informed me that the pink sticker on the card is an axolotl, a creature that lives in water in Mexico. Apparently, axolotls are the latest craze among kids, replacing unicorns, Pokémons, dragons etc. so you may be hearing about them.

Mexican axolotls are a type of salamander that never develops beyond the juvenile larval stage and rarely, if ever, leaves the water. They breathe oxygen dissolved in the water by waving their sets of three frilly, external gills located on each side of their heads. Mexicans call them “walking fish” because they both walk on their four legs underwater and swim with the aid of paddle-like fins on their back and long tail. They are unable to walk on land.

Axolotls are 23-25 cm long on average, making them giants in the salamander world and some may grow even longer.

Axolotl is an ancient Aztec name meaning “water dog” from the Aztec's belief that they were a revered Aztec god (Xolotl) with a dog’s head.

The axolotl head is proportionally large with big eyes and lacks eyelids in the males. They have large mouths with which they suction their food consisting of small fish, molluscs and arthropods as well as even tinier aquatic creatures.

Axolotls possess several genes for pigmentation so they can appear pink, black, brown or translucent white and can change colour throughout their life. Regeneration of limbs has been documented as occurring up to six times, but so far almost nothing is known about how they die.

The males appear to “dance” by wiggling their tails before releasing a cone-shaped sperm mass. The female is attracted to the tail-wiggling and when he is done, she will pick up the sperm mass and fertilization of the eggs takes place internally. Between 300 and 1,000 eggs may be released and fastened to surrounding rocks to protect them from predators.

Axolotls are only found in one area of wetlands, ponds, and lakes including Lake Xochimilco in Mexico City. They used to be more abundant, but their habitat has been, and still is being, reduced due to the development of Mexico City. They are now listed as an endangered species.