Weird Animals - the Wooper Rooper - Axolotl

The axolotl (pronounced AHK-so-LA-tuhl) is a rare Mexican salamander that forever looks like a teenager. Not a human teenager – though I have seen a few human teen specimens who look peculiarly like axolotls. I’m referring to the fact that throughout its adult life, the axolotl has the rare capability of retaining its larval features. It looks forever young.

What is neoteny?

Larvae of the axolotl fail to undergo metamorphosis, so the adults remain aquatic and gilled. This condition, called neoteny, means it keeps its tadpole-like dorsal fin, which runs almost the length of its body, and its feathery external gills, which protrude from the back of its wide head.

Axolotls (Ambystoma mexicanum) live exclusively in the lakes, channels and wetlands that comprise the Xochimilco Lake complex underlying Mexico City. They are the best-known of the Mexican neotenic mole salamanders related to the Tiger Salamander family.

But they differ from most other salamanders because they live permanently in water. In extremely rare cases, an axolotl may progress to maturity and emerge from the water, but the majority are content to remain underwater as outsized larvae. Males and females mate underwater and the females lay eggs on nearby structures such as plants.

Walking Fish, Water Dog or Wooper Rooper

Often referred to as “walking fish,” axolotls are salamanders, not fish, and confine their walking to the bottom of the lake or aquarium. The name, axolotl, is derived from the Aztec term, nahuatl, which means “water dog.” They are often purchased as pets in the U.S., Great Britain, Australia and Japan. The Japanese refer to them as “wooper rooper” (u-pa-ru-pa).

They measure up to 12 inches in length and may weigh 2 3/4 to 8 ounces. In their natural habitat, they are usually black or chocolate-brown and sometimes cream-colored. In captivity they are gray, shades of brown, white with black eyes, golden albino, pink, even multi-colored. That variety is known as he “harlequin Mexican walking fish.”

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People and most animals are able to sufficiently heal a cut, replace portions of dead or damaged skin, or even regenerate a small portion of an internal organ. But axolotls have the unique ability to completely regenerate not just their limbs and tail, but even heart and brain cells! Listen up, Dr. Frankenstein. Instead of merely forming scar tissue over a wound, the axolotl can regenerate entire body parts, including gills, eyes, kidneys, even large portions of its liver.

If it loses its tail, it can eventually replace it – skin, muscle and all. Even portions of its spine and brain can be regenerated, something which is near-impossibility with almost every other vertebrate. Juvenile axolotls seem to be able to regenerate body parts quickly, while adults either replace parts more slowly or not at all.

Axolotls are used extensively in scientific research due to their ability to regenerate most body parts, ease of breeding, and large embryos. These unique qualities have caused them to be one of the most scientifically studied animals in the world.

Axolotls are fairly long-lived, surviving 10 to 15 years on a diet of mollusks, worms, insect larva, crustaceans, and some tiny fish. Accustomed to being a top predator in its habitat, this species has begun to suffer from the introduction of large fish into its lake habitat. Large numbers of these fish, both carp and tilapia, compete ecologically with axolotls for food, and also eat axolotl eggs. Natural threats include predatory birds such as herons.

Axolotls are becoming "ax-o-littles"

Populations of axolotls are in decline and disappearing as the demands of nearby Mexico City (over 18 million people) have led to the draining and contamination of much of the waters of Xochimilco Lake. They are also popular as pets for tropical-fish-lovers, and roasted axolotl is considered a delicacy in Mexico. Scientists continue to use them in research studies, further shrinking their numbers.

For these reasons axolotls are listed as endangered and on the verge of becoming extinct on the annual Red List of threatened species. Recent surveys suggest that only 700 to 1,200 axolotls survive in six scattered areas within the Xochimilco area of the Mexican Central Valley.

© Copyright BJ Rakow Ph.D. 2010, 2011. All rights reserved. Author, "Much of What You Know about Job Search Just Ain't So," 

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