Axolotl (Ambystoma mexicanum)

"Ambystoma mexicanum 1" by Stan Shebs - CC-BY-SA-3.0

“Ambystoma mexicanum 1” by Stan Shebs – CC-BY-SA-3.0

Our newest addition to the cabinet comes by special reader request, collected by Cecilia Larraga! Its name, from the Aztec Nahuatl language, means “water monster,” and it’s also known as the Mexican walking fish, but the axolotl is neither a fish, nor can it survive out of water. Its unique lifestyle and almost non-existent range (not to mention its ability to regenerate) make it a curious creature, to say the least!

I don’t want to grow up

Unlike most salamanders, axolotls never go through metamorphosis. With the odd exception, they stay in their larval stage for their entire lives, a condition known as “neoteny.” This is partially what gives the species its bizarre look, since axolotls keep their tadpole dorsal fin, as well as the feathery external gills that stick out like a strange headress. Since they never develop air-breathing lungs, axolotls spend their entire lives underwater. Staying in tadpole stage doesn’t prevent axolotls from reproducing, however; they mate underwater and the females lay their eggs on plants and other available surfaces.

They’re normally black or brown, but pink or white albinos are commonly found in captivity – and sadly, captivity is almost the only place where the fascinating creatures still exist these days. Found only in the former Lake Xochimilco complex in Mexico City, the axolotl has taken a beating as the city grows. Lake Xochimilco and Lake Chalco have been gradually drained to reduce flooding risk and make room for expansion; Chalco has totally disappeared, and the axolotl now clings on in a few remaining canals and small lakes.

Ambystoma mexicanum Photo © Biopix: N Sloth

Ambystoma mexicanum by Biopix: N Sloth – CC-BY-NC

According to research by Dr Luis Zambrano of the National Autonomous University of Mexico, the critically-endangered species lives in only six isolated parts of the Xochimilco system, usually near springs that still have clear, fresh water. Zambrano’s team says there may be only 700 to 1200 individuals left in the wild. Water pollution is another reason the population has crashed; it also has to deal with competition from introduced fish like tilapia and carp. Unfortunately, using reintroductions to boost the wild population might be dangerous, since it would risk introducing the chytrid fungus currently wreaking havoc in amphibians worldwide. However, the axolotl is widespread in captivity – it’s extremely popular both as an aquarium pet, and as a subject of scientific research.

Hey, take a look at this trick!

Biologists are fascinated by the axolotl because it’s an amphibian that never grows up – giving it an amazing ability to regenerate. The species can re-grow entire limbs, heal parts of spinal cord, and even portions of the brain. Axolotls can recover from massive injuries – and can heal over and over again, with no sign of scarring. And it gets better – they’re also over 1,000 times more resistant to cancer than mammals. Scientists are exploring how these unique “superhealing” abilities work, with the hope of (eventually) being able to heal human tissues, improving success for burn victims, transplant recipients, and even cancer patients.

The question is what the chances are for wild axolotls in the meantime: Zambrano and his team are trying to create wild refuges so that these populations, too, can bounce back. The restoration of the Parco Ecologico Xochimilco over the last 20 years is one of the projects to reclaim crucial habitat for this one-of-a-kind animal.

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