The salamander is an endangered species known as a "walking fish" but is actually an amphibian.
First published in 1954, Julio Cortázar's short story "The Axolotl" shows a Latin American man living in Paris who becomes obsessed with the axolotl in a zoo and eventually becomes a newt. They have "pink Aztec faces," "golden eyes," and "small rose-colored bodies, translucent..." and finally an extremely delicate fishtail," and the narrator observes that "there is no resemblance between salamanders and humans." Consider these feathers, the pink salamander, "seems easy, almost obviously, to fall into myth." ”
On the face of it, Cortázar's narrator is correct in his estimates of axolotls or Mexican walking fish. First, the axolotl entered mythology centuries ago – the Aztecs believed that the first axolotl appeared in the lake system around modern-day Mexico City, when Xolotl, the powerful underworld god, transformed himself into a small, feathered amphibian in order to escape capture.
In ancient Mesoamerican cultures, these close relatives of tiger salamanders were thought to be the source of food provided by Lake Xochimilco for humans.
Cortázar's idea that axolotls resemble humans is correct – our last common ancestors may have roamed the Earth 360 million years ago, and at first glance, they are very different from us.
Among the first modern zoo animals, in 1864, 34 axolotls (along with three deer and three wild dogs) were brought from Mexico to the zoo in Paris. Although they weren't as interesting to 19th-century zoogoers as the larger, charismatic animals, scientists quickly realized that these humble little animals were strange — in fact, almost mythical.
Axolotls live underwater
The axolotl is a large, endangered salamander species that lives in freshwater – as their name suggests, they are not actually fish at all. In the wild, they are usually dark brown or black with spots, but white or albino variants are common and you often see them as pets. With a round head and an ever-smiling face, wild axolotls are adorable – one of the reasons they are favored by pet owners in the pet trade. One reason they are cute is that they are juvenile, meaning they retain many of the characteristics of their juvenile years as adults.
For example, while adult axolotls also have the same lung function as other salamanders and can breathe through their skin, they have large, fluffy external pinnate gills — most amphibians don't have them when they are juvenile. They have small, delicate webbed feet and a long tadpole-like tail with translucent fins in the tail, as they do not need to rely on webbed feet and legs to walk on land, but they must be able to move through water like large tadpoles.
Scientists believe they remain infant-like throughout their lifespan because, unlike other salamander species, wild axolotl populations evolve in very stable habitats. Most other salamander species, such as the tiger salamander, live in wetlands that dry up at certain times of the year, so they must remove their feathery gills and breathe through functioning lungs and skin. Wild axolotls evolved in habitats with water year-round and few aquatic predators, so they don't need to spend energy changing their bodies to adapt to changing environments.
Lifespan of axolotls in captivity is about 15 years, while axolotls in the wild may live only 5 to 6 years. They reach sexual maturity at the end of the year, and although they are solitary creatures most of the time, in February, the breeding season begins and wild male axolotls begin to use pheromones to find females. When they are together, the male will dance courtship and wag his tail in the direction of the female. After the female acquiesced in its attention, the female poked it with her nose, and she placed a sperm packet at the bottom of the lake, which the female picked up to fertilize her eggs.
Female wild axolotls lay hundreds of eggs around weeds or rocks and then let them fend for themselves – young axolotls have no parental care. In fact, it has been observed that small axolotls hatching from eggs gnaw on the legs and tails of their siblings to stay alive when hungry. This is completely fine because the legs grow back quickly.
In their home ecosystems, axolotls are — or at least were — apex predators around lakes, wetlands and canals in central Mexico. They are unusual among amphibians in that they spend their entire lives underwater and breathe with their gills, while most other salamander species walk on land and breathe with their lungs in adulthood. Although they may seem inconspicuous, they are actually ruthless carnivores, feeding on worms, molluscs, insects and insect larvae, and even eating small fish in the wild.
Part of the Aztec mythology revolves around the fact that they are like a powerful god and are difficult to kill. If axolotls lose almost any part of its body, it can regenerate without problems. Some lizards can grow tails, flatworms split in two can grow the other half, starfish can regrow limbs, and axolotls can regrow almost any part of their body in a matter of weeks.
A newt, such as this spotted white axolotl, can live happily for up to 15 years in captivity, but only 5 to 6 years in the wild.
Of the animals closest to us, vertebrates, salamanders are the only ones that can regenerate in this way and heal without scarring. Other salamanders can also regenerate, but axolotls do the best.
When Europeans heard the wind of axolotls regenerating, they went from boring exhibits in zoos to one of the most important and long-lasting self-sustaining laboratory animals in history. George Cuvier, widely regarded as the father of paleontology, studied axolotls to try to figure out whether Carl Linnaeus's classification of separating amphibians from reptiles was correct — a big problem at the time, and Cuvier concluded that axolotls breathed through the gills all their lives and must be some kind of lizard that existed as a permanent larva — in the words of paleontologist Stephen Jay Gould, a "sexually mature tadpole."
Because axolotls perform so well in laboratory and aquarium environments, 19th-century zoologist August Dumsamir supplied every laboratory in Europe with a large number of axolotls, which led to some truly terrifying studies in which scientists shredded axolotls in the lab just to test the limits of their ability to regenerate.
The miracle of axolotl regeneration
Today, salamanders are a very important model system for us to study regeneration. For decades, even centuries, we have known that we can remove a part of the developing embryonic structure, and the cells left behind will fill, repair and regenerate that structure. But in most animals, such as mammals, this system shuts down at the end of embryonic development. Axolotls and other salamanders appear to be able to return to their embryonic state, re-entering developmental procedures that already exist. Humans have this program, it's just that we can't use it when we're no longer embryos. You could say that we, like axolotls, have evolved the ability to regenerate, but we've also evolved a mechanism to inhibit regeneration.
Scientists are interested in axolotls because they hope to one day apply its miraculous limb regeneration abilities to humans. Axolotls can regenerate new limbs, heart tissue, eyes, and even the spinal cord and parts of the brain and produce new neurons during their lifetime, and the human brain can do the same, although not so easily.
By injecting a salamor with iodine or thyroxine, or feeding it iodine-rich foods, it is possible to transform it into an adult salamander without gills. However, the scientists found that they do not easily regenerate cells after they are deformed.
Wild axolotls are critically endangered
Wild axolotls may have evolved the ability to regain embryonic instructions to regenerate organs and limbs — captive axolotls could even endure living in a filthy 19th-century aquarium or laboratory, cut into tiny pieces — but what they couldn't stand was that their home ecosystems were overwhelmed by introduced predators, environmental toxins and habitat degradation. The lake they live in near the highly urbanized city of Mexico City is not only polluted by aging wastewater systems, but also flooded by introduced tilapia and sea bass, both of which treat axolotls as a delicious snack.
In 1998, scientists calculated that Lake Xochimilco had about 6,000 axolotls per square kilometer, but that number is now close to zero. Since 2006, the International Union for the Conservation of Nature and Natural Resources has listed axolotls as critically endangered, and a 2019 population assessment concluded that the number of axolotls in the wild may be less than 1,000.
The Mexican government and many axolotl conservation groups across Mexico are doing their best to save threatened salamander species by restoring the lakes and natural habitats in which they live. One strategy is to build fixed floating island habitats for them, rafts made of aquatic plants, mud and wood, used as floating gardens in ancient Mesoamerican cultures. Hundreds of years ago, when the Aztec capital, Tenochtitlan, was located in Mexico City's location, the Aztecs built and farmed on a vast network of Chiangpa that surrounded the capital for miles. This agricultural system created shallow and sheltered canals where axolotl populations increased considerably. When European conquistadors arrived in 1519, they destroyed the Aztec civilization, drove out the Chiampas, drained the canals and lakes – things that continue to this day.
Today, the natural habitat of wild axolotls is limited to Lake Xochimilco south of Mexico City. Efforts are underway to weed out invasive fish that feed on axolotls and begin cinampaz-based agriculture at Lake Xochimilco, where aquatic vegetation not only provides habitat for salamanders but also filters toxins from the lake's water. Chiangpa's ecotourism has funded efforts to protect axolotls.
While wild axolotls are not very abundant, they are good in captivity – they are the most widely distributed amphibians in the world. While the study of axolotls is scientifically important, captive pet axolotls are also popular — especially in Japan, where you can also eat salamanders as a fried snack in some restaurants.
Pet owners are not legal everywhere to own a pet axolotl, so it's important to check local exotic pet laws before you get a pet. Because they are entirely aquatic, it's important to fill the tank completely – a 57 to 151 litre tank is best. Just like pet fish, you should never pick up or handle axolotls, and you should not put them with other pets, whether fish or other salamanders, because they are difficult to get along with.