May 4 – Forever Young

Today’s Factismal: The axolotl salamander becomes an adult without ever becoming a teenager.

Like most amphibians, salamanders are born from eggs laid in water. They swim around for a couple of months before undergoing a metamorphosis where they lose their gills, grow legs and teeth, and head for the hills to feed on other small critters and find other salamanders to continue the species. But when salamanders live in small lakes that are poor in oxygen and food and surrounded by dry wilderness, the salamander may skip the metamorphosis and become a mixture of sexually mature adult and gill-bearing child. This unique state is called neoteny (“keeping childhood”) and is found in almost all species of salamander in exceptional circumstances.

AN axolotl adult smiling for the camera (Image courtesy LoKiLeCh)

An axolotl adult smiling for the camera
(Image courtesy Amphibian Rescue)

But one species makes a habit of the exception. The axolotl salamander, which lives in central Mexico and was a popular food for Aztecs, never becomes a full adult; instead, all of the axolotl (an Aztec word for “Water Monster”) are neotenic. They become full adults without ever being teenagers. They do this because the axolotl is found in only two lakes (one of which is now dried up and the other of which is being drained by Mexico City), both of which are surrounded by desert; they have always lived in exception circumstances and always will.Unfortunately, those same circumstances mean that the axolotl is a critically endangered species in the wild.

A "Water Monster" walking along the bottom (Image courtesy LoKiCheh)

A “Water Monster” walking along the bottom
(Image courtesy LoKiCheh)

But the news isn’t all bad; though they are rare in the wild, axolotl are plentiful in the lab. They were the first known neotenic species and have been popular lab subjects and pets since 1863 when the first specimens were shipped to Paris for research. Interestingly, many evolutionary biologists believe that humans are also neotenic and frequently cite the axolotl as an example of how such a species can thrive.

Unfortunately, salamanders aren’t thriving, not everywhere. In addition to the critically endangered axolotl, there are several species of endangered salamander in North America. If you’d like to help scientists track salamanders and maybe learn more about neoteny, then why not join the North American Amphibian Monitoring Program?
http://www.pwrc.usgs.gov/naamp/

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