Sporting a headdress of feathered gills and tiny webbed legs, the Mexican axolotl’s alien-like appearance makes it a global treasure. But axolotls aren’t just adorably cute. Named after the god Xolotl, who tried to avoid sacrifice by transforming into this unique salamander, the creatures have the remarkable ability to regenerate lost or damaged limbs, hearts, spinal cords, and even parts of their brains.
And that’s not all. They also stay “young” throughout the entire course of their lives. In this respect, the axolotl could hold the secrets to regeneration within its very cells.
But there’s a problem. Axolotls can only live in one tiny area in the wild. Located in Lake Xochimilco, just to the south of Mexico City, this icon of Aztec culture is on the brink of extinction.
What is an axolotl? They seem a lot like fish, as they are fully aquatic and keep their gills for their entire lives. But they are actually a kind of salamander, which means that axolotls are amphibians. They can live up to ten years and may grow to be 30 cm (1 foot) long.
Weighing in at only 300 grams (8 oz), this small creature has the second-largest genome in the animal kingdom. With 32 billion base pairs, they are just behind the lungfish. For reference, humans only have three billion base pairs in their genomes. This means that each cell in an axolotl contains 10x more DNA compared to humans.
However, axolotls don’t have more genes. Instead, they have more repeated DNA sequences. Studies show that these duplications are a possible stress response to environmental factors, such as climate change or a new pathogen. Experts think that this could indicate that the salamander species is much further along in its evolutionary story compared to species (like us) with less repetitive genomes.
Although the axolotls’ regenerative abilities may seem like the stuff of fantasy, scientists actually have a pretty good understanding of how it works.
Through genome sequencing, scientists discovered the source protein behind the creatures’ regenerative powers. Surprisingly, this protein is not rare across species. Humans have it too. The difference is that humans lose this growth mechanism with age, whereas the axolotl remains in its juvenile form throughout its lifetime. In other words, axolotls essentially never really grow old.
How does it work? In short, a layer of stem cells is called to the wound site to recreate the area from scratch, leaving no signs of the previous damage. This gives the animals the ability to grow back missing limbs, tails, eyes, brains, and more. A severed spinal cord isn’t even a match for its regeneration powers.
How axolotl regeneration works: a deep look
In order for an axolotl to regenerate an entire limb, the tiny creature first needs to stop bleeding. To this end, a clot of blood cells quickly travels to the injury to stop the blood. Next, a thin layer of cells forms over the wound site to cover the area where to amputation occurred. This thin layer is known as a “wound epidermis.”
Over the following days, these cells grow and divide. Once this process is far enough along, cells underneath the wound epidermis known as “blastema cells” start to divide and lose their identity. In short, the blastema cells de-differentiate and, in so doing, gain the ability to grow into different kinds of cells that make up the body — bone, cartilage, muscle, and so on. Notably, the blastema cells can’t grow into any type of cell. A cell that used to be a muscle can only re-form different types of muscle cells. But all the same, this de-differentiation allows the axolotl to create the cells that it needs to heal.
Eventually, the blastema cells grow and multiply until they regain an identity as fully-developed bone or skin cells. This growth process continues until the damaged area resembles a perfect copy of the lost limb.
In the United States alone, some 185,000 amputations occur each year. However, scientists believe that figuring out exactly how and why axolotls don’t scar could unlock humanity’s ability to regenerate tissue. This could be life-changing for burn victims, cancer patients, and (of course) amputees.
Yet, scientists still have much to learn about this revolutionary animal in order for this dream to be realized, and they are racing against its possible extinction to learn all they can.
An ancient population in peril
During Pre-Columbian times, the axolotl population thrived among the Aztecs’ floating gardens, traditionally known as “chinampas.” These gardens were perfect for the axolotl, as they created long shorelines and productive wetlands, and the creatures multiplied greatly. As a result, the amphibians eventually became a reliable food source for the Aztecs and their descendants. It not only made its way into their stomachs but also into their art and mythical creations.
However, after the fall of the ancient empire, this aquatic habitat gradually deteriorated until the 20th century, when it fell into complete despair.
Originally, axolotls lived in two lakes in Mexico City. However, one of the lakes was drained and the other only exists today in the form of canals. Thanks to urbanization, invasive fish populations, and water pollution, the habitat is no longer suitable for the wild axolotls.
Axolotls are listed as critically endangered by the IUCN Red List of Threatened Species. It is suspected that the wild population has declined by 80% or more over the last three generations. A study published in BioScience shows there could be less than 35 individuals per square kilometer in the canals of Xochimilco — down from about 6000 per square kilometer (2300 sq. miles) in 2000.
Yet, axolotls are a very popular creature, and they have a high distribution in captivity across pet stores, restaurants, and research labs. But although the number of axolotls in captivity might seem like a good thing, it doesn’t solve the problems scientists face.
Unfortunately, the large population in captivity will not save this species. It has led to inbreeding, which impacts the axolotl’s genetic diversity and susceptibility to disease. What’s more, captive axolotls have been crossbred with tiger salamanders. This has dramatically altered their DNA, making them almost like an entirely different species.
Soon, biologists could lose the irreplaceable clues hidden within their DNA. Fortunately, people are becoming more aware of the axolotl. Unfortunately, our increasing love for the cute axolotl has only made things worse.
Minecraft, TikTok, and axolotls
In 2021, Minecraft added axolotls to its universe. In the game, the tiny creatures are usually pink and can be found around caves and caverns. The rarest axolotls in Minecraft are blue, but all colors of axolotls are highly coveted by players. According to trends found in Google’s trend reports, searches for “axolotl” peaked when Minecraft introduced them in July 2021. However, the number of searches has remained elevated ever since.
The creatures also became widely popular on TikTok over the course of 2021. At the time of writing, the axolotl hashtag on the platform has accumulated more than 2.8 billion views.
This is a problem. The surge in popularity in the digital realm spawned a surge in the number of people trying to acquire them as real-life pets. And it seems that the owners don’t understand how to properly take care of the creatures.
For starters, axolotls breed remarkably fast. According to The Guardian, owners unknowingly put breeding pairs together in tanks. There, they ended up having accidental clutches, and some owners were left with thousands of them. Although some owners attempted to bring the axolotls to pet stores for potential adoption, experts fear that others released them into the wild, where they may reproduce with local endangered species of salamanders and “wreak havoc on an ecosystem.”
It’s important for individuals to understand how to responsibly care for the cute axolotl, as local species’ lives are literally on the line.
How to save the axolotl
Amphibians breathe through their permeable skin, making them more vulnerable to pollution. Therefore, water quality needs to improve. Additionally, in their larvae the stage axolotls are preyed upon by overpopulations of introduced fish, so protection must be provided.
Unfortunately, structures surround the historical lake where they live, which means their habitat cannot be restored and a new one is in order. Fortunately, solutions could possibly be found by turning to the past.
Some local farmers still use chinampas. These agricultural canals are now shielded from invasive fish, providing a refuge for the relocated axolotls. The improved water quality within these areas also creates a mutual relationship between the endangered amphibians and local producers.
Politicians are beginning to notice this success and enact protection plans — both in Mexico and beyond. Today, most countries don’t allow the species to be traded across international borders. This is largely due to concerns that they’ll be poached from the wild. Axolotls are also illegal to own in several U.S. states for these reasons.
Let’s hope these efforts succeed, as the fate of the species rests on the conservation of the wild axolotls within the Xochimilco region.
- The word “axolotl” comes from the Nahuatl language of the Aztecs. The word literally translated means “water dog.”
- Colloquially, the species is often called “the Mexican walking fish.” However, as mentioned, it’s not a fish at all
- In rare cases, axolotls have matured past the larval stage and emerged onto land as adult salamanders.
- Axolotls are naturally dark-colored. But they can shift their hue a few shades lighter or darker for camouflage.
- The pink and other light-colored axolotls you see? They have been bred by humans because we think those shades look “cute.”
- The animals can only be found in the lakes and canals of Xochimilco, Mexico. It’s a small area that’s ripe with pollution and invasive species that eat axolotl.
- Their closest relatives are the tiger salamander Ambystoma tigrinum, and its slightly more distant relative is the spotted salamander Ambystoma maculatum.