Biodiversity | Mexico

The incredible transformation of the axolotl

The iconic axelotl has fascinated Aztecs, scientists and became a meme. But is that enough to bring it back from the brink of extinction?
A colorful illustration shows axolotls

Revered since Aztec times and a Mexican national icon today, Axolotls are struggling to survive in the wild

 

It looks like a small sea monster, like an ancient creature from a lost world. For me, everything started with the axolotl. Even as a small boy I was fascinated by this ‘water monster’, which I caught on the shore of a lake to play with. The mysterious tailed creature sparked a childlike naturalist’s enthusiasm in me, which led me to study biology.

Later, I experimented to artificially induce the metamorphosis of the little swamp monsters. It kept me so busy that I wanted to somehow put the whole thing into words, a desire that eventually led me to literature. But this unusual animal fascinates not only me, but has a huge following spanning science, literature, religion and folklore.

What makes it so fascinating? The axolotl measures between 15 and 45 centimetres and belongs to the salamander family. All salamanders - around 630 species worldwide - begin their lives as axolotls before they grow, leave the water and morph into land animals, i.e. salamanders and newts.

The exception to this are four Mexican species. They spare themselves the metamorphosis process and instead spend their entire lives in the larval stage - as axolotls. Thanks to a rare phenomenon known scientifically as ‘neoteny’, the axolotl still reaches sexual maturity.

“Its extraordinary ability to regenerate has earned the animal the status of a miracle creature”

In addition its unique way of reproduction, the axolotl has another characteristic that borders on the fantastic: its ability to undergo morphological regeneration. The axolotl is able to regrow lost limbs, hands, eyes, gills, the tail and even internal organs – and without any scarring. The new tissue is indistinguishable from the original and the process can be repeated as often as required.

Its extraordinary ability to anatomically regenerate gives the animal the status of a miracle creature in popular legend and allows modern medicine to dream up promising treatments. This ability would also explain why the builders of the city of Tenochtitlán (the capital of the Aztec empire dating from the 14th century and the contemporary site of Mexico City) saw the small sea monster as the reincarnation of a deity.

Its impressive ability lies in the transdifferentiation of the cells, which enables the cells of these amphibians to mysteriously rewind their development, and thus return to a malleable initial state. This means that they can return to a pluripotent form which can then develop into different types of tissue as needed.

I have often written about the axelotl; and now, once again, I am sitting here typing and thinking about whether certain animals embody the history of a country. There are organisms that reflect the worldviews and desires of certain societies like a mirror, possibly even revolutions, economic crises or artistic avant-gardes. I wonder whether this also applies to the axolotl and Mexico.

I wonder what the legendary amphibians have seen from the bottom of their swamp? Whether they witnessed shamans, monks, scientists, healers or the Tlatoanis, the Aztec rulers – some of the many people in Mexico who were mesmerised by the axolotl's extravagant physiognomy. Meanwhile, the axolotls saw them come and go, with the knowledge that they at least would prove to be a constant in their muddy habitat.

In fact, I cannot think of any other animal that has fascinated the inhabitants of Mexico as much as the charismatic Ambystoma mexicanum. The Toltec and Mexica peoples, as the Aztecs called themselves, saw it as the reincarnation of the god Xólotl, the twin brother of Quetzalcóatl, the great creator god.

According to the legend of the fifth sun, he refused to sacrifice himself like the other gods of the pantheon in order to set the stars in motion. When the executioner of the gods later captured him, he transformed himself into a two-stalked agave. When he was rediscovered, he jumped into the water and took on a fish-like form: a small swamp monster called an axolotl.

It is striking that all the organisms that the volatile god transformed into were considered essential foodstuffs in the regional cultures, and with the fall of Tenochtitlán and the arrival of the Catholic religion, the symbolic meaning of the axolotl changed dramatically.

It was accused of impregnating women in the lakes it inhabited - a belief that is still widespread in some rural areas - and of having a vulva and menstruating.

Meanwhile, eating it supposedly fuelled people's sex drive. These distorted views persisted until the beginning of the 19th century when, thanks to Alexander von Humboldt, the first samples of the axolotl landed in European laboratories.

In the following decades, the axolotl, with its strange life cycle and eternal larval stage, presented science with an unsolvable riddle - at least until the French intervention in Mexico in the 1860s. The French troops had an urgent mission to bring back several live specimens of the axolotle on their way back to Europe, where the French zoologist Auguste Duméril received the animals.

Not only did he succeed in keeping them alive, but a few years later, in 1866, he also observed and described their reproduction in the larval stage. The German naturalist Marie von Chauvin continued Duméril's research and even got the animals to undergo a metamorphosis to life on land in experiments that were innovative at the time.

Charles Darwin devoted several paragraphs to the phenomenon in his groundbreaking work ‘On the Origin of Species’. However, it was not until 1885 that Julius Kollmann coined the term ‘neoteny’ to describe the onset of sexual maturity in the larval stage. This put an end to hundreds of years of guesswork about the nature of the axolotl.

The transformative amphibians not only fascinated scientists, but also inspired poets in the 20th century. None other than Julio Cortázar, the Argentinian master of fantastic literature, created a monument to the animals in his story ‘Axolotl’ (1956) after encountering them in a Paris zoo and developing an obsession with them.

In it, the author plays with various narrative perspectives until he finally transforms himself into one of the amphibians. From then on, the amphibian became a frequent literary inspiration: It appears in the works of many Mexican writers, such as Juan José Arreola, Salvador Elizondo, Octavio Paz, Gutierre Tibón and other notable Latin American writers.

However, my favourite passage comes from the Mexican poet and essayist José Emilio Pacheco: ‘He is neither fish nor salamander, neither toad nor lizard, he has human features [...] and is an inhabitant of the intermediate world, of no man's land, of the habitat and grave of those who, through all our metamorphoses, have never penetrated to the truth of adult existence and therefore know and can do nothing but reproduce.’

This idea is taken up by Mexican sociologist Roger Bartra in his classic book ‘La jaula de la melancolía’ (‘The Cage of Melancholy’) as a metaphor for Mexico as a neotenic nation. He was also the author of the 2011 anthology ‘Axolotiada, vida y mito de un amfibiomexicano’ (‘Axolotiada, life and myth of a Mexican amphibian’), a colourful almanac that traces the history, literature and art of the axolotl.

Of course, the axolotl's widespread influence reaches even further. For example, its talent to morphologically regenerate has sparked the interest of medical research, in particular with a view to ward off certain types of cancer.

“The axolotl’s days are numbered, at least in the wild”

Against this backdrop, it is particularly ironic that the axolotl itself is fighting for survival. At present, it is threatened with gradual extinction, partly due to the introduction of fish species such as tilapia and carp, which are disrupting the food chain, partly due to the destruction of its habitat in Mexico City, one of the world's largest megalopolises, and partly due to water pollution from sewage treatment plants.

The axelotl’s population has plummeted with dizzying speed, from 6,000 specimens per square kilometre in 1996 to well under one hundred barely two decades later. Today, you are lucky if you spot a few specimens in one of the canals of Xochimilco, the ‘floating gardens’ in Mexico City, the last refuge we have for the creatures still living in the wild.

The days of the axolotl seem to be numbered, at least in their natural habitat. In captivity, however, it is omnipresent, both in research laboratories and on the globally flourishing market for exotic pets.

Here it can be found in a wide range of different colours: from the light pink albinos to the leucistic ‘whites’, from golden and black to spotted specimens. There are breeding farms everywhere, and if this development continues, it could well be that the axolotl will eventually evolve into a kind of ‘amphibian dog’ that, like our pets, becomes more distant from the wolf with each new generation. This raises the question: what the point  of an animal condemned to spend its entire life in aquariums?

No matter how many specimens are caged, the species as a whole can never be captured. A species is much more than its individual components, it is the distinctive system that emerges from the interaction of a particular group of animals with their surrounding enivronment. For this reason, the species is currently practically invisible.

For the time being, however, the amphibian can be found as an image on the Mexican fifty-peso note. But take a moment to reflect on what all the figures on our banknotes have in common: They are all dead.

This fact serves as a bitter reminder that we so often only recognise the value of something when it has almost disappeared. But perhaps we can seize the opportunity to belatedly appreciate the axolotl with all its qualities. Although in times of climate crisis and excessive greed it appears as a candidate for imminent extinction, it is still possible to turn the tide: We can halt our short-sighted behaviour and forge a future that will be more kind to us and our fellow creatures.

I would like to believe that, over time, the axolotl will evolve into a new symbol: an icon for the how we conserved nature and overcame the pitfalls of the Anthropocene.

Translated by Jess Smee