Their gills flap like carnival feathers. Their bodies are as slippery as slugs. They can even grow extra fingers. Their name means “water monster” in Aztec. They are the amazing Axolotls, also known as the Mexican Walking Fish. Scientifically known as Ambystoma Mexicanum, axolotls belong to an order known as Caudata, which includes amphibians such as salamanders and newts.They are only found in Lakes Xochimilco and Chalco in Central Mexico, near Mexico City. Due to the rapid urbanization of Mexico City and the resulting water pollution, as well as invasive predators, these animals have become critically endangered in the wild. Most axolotls, whether they are pets or used as research animals, originate from captive populations. But that’s not why they’re different from other salamanders.
Axolotls, unlike most salamanders, don’t experience metamorphosis. This means that axolotls become sexually mature while never leaving the larval stage, and thus, live with gills for their entire lives, a process known as neoteny. This occurs because they lack the thyroid stimulating hormone, which impacts the regulation of growth hormone. As the name suggests, these are important in regulating growth. When human children have iodine deficiency, an important chemical element in Thyroid Stimulating Hormone, they experience thyroid hormone deficiency, which results in stunted growth and reproductive failure. Because of this, axolotls are used to further explore neoteny and thyroid hormone deficiency in other organisms such as humans. When they are exposed to a greater concentration of iodine in their habitat, however, they can produce thyroid hormones more easily and grow to the adult stage, losing gills and growing fully functional lungs. The fact that axolotls have thyroid hormone deficiency makes them important for research in this branch of medical science.
These animals possess an even more amazing adaptation: the ability to regenerate limbs that show no sign of damage. Axolotl regeneration does not end there; they can regenerate internal organs, parts of the brain, bones and even spinal cords. If that’s not cool enough, axolotls will not reject body parts transplanted from other axolotls. Many scientists have been performing various experiments on axolotls in order to better understand their regenerative process, and hopefully find the key to trigger regeneration in humans. According to Professor Stephane Roy from the University of Montreal, axolotls begin their healing process by altering cells in the wounded area into ones that lack individual characteristics. This means these cells essentially become stem cells. These newly formed stems cells, also known as dedifferentiated cells, form a congregate known as a blastema that covers the wounded region. Later, the stem cells become more specialized (or reinitiated) and grow into a new, fully functional limb or organ. Scientists like Roy believe that this regenerative ability can later be artificially triggered on humans. Of course, humans do have some regenerative properties such as regeneration of the skin and fingertips. It is commonly known that a liver, even reduced down to 25% of its original mass, can heal into a fully-functional liver, back to its original size. Even so, liver regeneration only occurs slowly. This can mean that it might take longer for a liver to regrow than one’s body is able handle a damaged liver. If regeneration can be triggered on humans in the future, it could be possible that humans can regrow skin damaged by burns, or regrow organs without the need to wait years for donor organs.
Through years of research, scientists are finally starting to understand why axolotls experience neoteny, and more importantly, how axolotls are able regenerate complex body parts. At this point, scientists are striving to understand the mechanics of this animal’s regenerative ability, and hopefully be able to apply them to address human maladies.