Axolotl: The Most Outstanding Animal That Refuse to Grow Up

Axolotl: The Most Outstanding Animal That Refuse to Grow Up

By Mr Ghaz, November 6, 2010

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Axolotl: The Most Outstanding Animal That Refuse to Grow Up

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When The Scottish playwright Sir James Barrie created the character of Peter Pan, the boy who refused to grow up, he probably did not realize that nature had beaten him to it. There are several creatures in the animal world that refuse to grow up. The most outstanding is the axolotl.

Aztec Monster

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The axolotl is an amphibian – one of a group of animals that spend their lives both on land and in water. In the wild, the axolotl is found only in Lake Xochimilco near Mexico City. It takes its name from the Aztec word meaning “water monster.”

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For years people were baffled by the axolotl. It looked like an immature or larval form of salamander, yet it was sexually mature and able to breed. Then, in 1865, French scientists made an amazing discovery: the axolotl was in fact an immature salamander. Several young specimens on laboratory tanks were spontaneously changing into adult salamanders; they began to lose their feathery gills and develop longer tails.

A Child at Heart

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The axolotl is one of a number of creatures, including some other salamanders and several species of newts that retain their juvenile form in later life – a characteristic known as neoteny. However, the axolotl advances one stage further than this: it develops sexual organs so that it can reproduce. Scientists have labeled this phenomenon paedogenesis.

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What is the reason for the Peter Pan behavior, and what makes the axolotl suddenly grow up? Laboratory experiments show that adulthood can be induced by adding iodine to the water in which the axolotl lacks a hormone called thyroxine, which is produced in the thyroid gland. Iodine helps to stimulate thyroxine production. Apparently, a physical jolt can have the same effect: some axolotls change into the adult form after a bumpy journey from one laboratory to another. At other times, the change can occur spontaneously, for no apparent reason.

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In their Mexican lake home, axolotls exist in both forms, but the immature ones greatly out-number their adult counterparts. It may be that something in the composition of the water of the lakes causes the Peter Pan syndrome.

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But there is another possible reason. Lake Xochimilco is surrounded by dry, bare land – a desolate habitat that provides little food for an adult salamander. By retaining its juvenile from, the axolotl can spend all its life within the safe confines of the water.