gerontakos: Αξολότλ: το αμφίβιο που αναγεννά τα κατεστραμμένα μέλη του

Σάββατο, Νοεμβρίου 16, 2019

Αξολότλ: το αμφίβιο που αναγεννά τα κατεστραμμένα μέλη του

Frankie was missing half his face. A fungal infection had come over the little axolotl, a native amphibian of the waterways of Mexico City.
But Frankie, along with other axolotls, have a special talent. Veterinarian and axolotl researcher Erika Servín Zamora, who was also Frankie’s caregiver, said she was astounded to see the animal’s remarkable regeneration abilities that she’d read about in her studies. Within two months, Frankie had grown a new, fully functional eye, and life was back to normal in his tank at the city’s Chapultepec Zoo.
Frankie might not have been so lucky in his native habitat, just about 30km south of the zoo. The axolotl, though gaining traction as a symbol of Mexico City, and specifically of the southern borough of Xochimilco, a Unesco World Heritage site, is nearly extinct in the wild due to increases in invasive fish species and water pollution in the city’s troubled canals. Making things worse, Frankie is an albino axolotl, which means he’s light pink with frilly, pink gills coming off his head – he’d be easy prey for Xochimilco’s invasive tilapia in the dark, murky waters.
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Known locally as “water monsters”, axolotls have a love-them-or-leave-them appearance. For some, these 20cm-long, soft-skinned, water dwellers are considered adorable, with the appearance of a perpetual smile. For others, these four-toed amphibians are just plain odd.
Despite their somewhat polarising looks, they are of particular interest to scientists hoping that axolotls like Frankie just might teach us humans the regeneration trick someday.
“Scientists are looking to benefit from the regenerative properties of axolotls by applying them to people who are injured in accidents, wars or suffering illness – people who lose limbs,” Servín Zamora said. “Others are looking for ways that axolotl regeneration can benefit human organs, such as by healing the heart or the liver.”
Axolotls are also helping Servín Zamora and other scientists understand the apparent resistance to cancer that all amphibians seem to have. “In 15 years, I have not seen any cases of malignant tumours in axolotls, which is interesting,” she said. “We suspect that their ability to regenerate cells and body parts helps them in that respect.”
And that's not all. Axolotls have been used traditionally throughout Mexico as a remedy for conditions associated with things like pregnancy, frailty and respiratory illness. A group of nuns in Patzcuaro, Mexico, legally breeds one axolotl species, ambystoma dumerilii, and uses the animals as an ingredient in cough syrup, though traditionally they were consumed as part of a broth.
Perpetual teenagers – and representations of the divine
Frankie is an ambystoma mexicanum, one of the 17 species of axolotl in Mexico. Found primarily in the states of Mexico, Puebla and Michoacán, many are critically endangered. Some species transform themselves into earth-walking salamanders by losing their tadpole-like tails and gills from their heads. However, this too depends on the environment. Frankie, for instance, living in captivity and therefore void of predators, will stay an eternal teenager. Never transforming into salamanders, axolotls like him will keep the tail they developed as a larva and live completely underwater.

Basically, they decide whether they will complete the metamorphosis

“Basically, they decide whether they will complete the metamorphosis, based on environmental stressors,” Servín Zamora said. “If they decide it would be better to live out of water, they will undergo the transformation into salamanders, but that can be a stressful undertaking in itself as they stop eating completely for that period. The current theory is that, for evolutionary reasons, the ambystoma mexicanum would remain in a juvenile state [somewhere between a tadpole and a salamander] because there was so much food in the water [such as charales, a small freshwater fish] and they had few predators, so there was little reason to emerge.”
Because of this tendency to change form, axolotls have a profound presence in Aztec (or Mexica) cosmogony. They were often recognised as a representation of Xolotl, god of the underworld and the malefic twin of the feathered serpent god Quetzacoatl, often represented as the sun.
When various gods were asked to make a sacrifice in order to create the world, Xolotl fled into the water. For his cowardice and reluctance to help, he was damned to live forever in the water and to suffer from eternal youth. For the Aztecs, death was transcendence, and to not complete that cycle meant being banned from reaching a higher realm.
A tourist attraction
Despite the axolotl’s endangered status, images of Frankie and his friends are plastered all over Mexico City, covering walls as street art and sold as plush toys in gift shops. An image of the ambystoma mexicanum axolotl will grace the 50-peso bill to be released in 2022. And Mexico City’s updated tour buses feature an image of an albino axolotl emblazoned on its double-decker sides.
Years ago, if you wanted to find an axolotl, all you had to do was look for a canal. Mexico City was built on the bed of what was once a massive lake, which the Aztecs used to create canals – as well as chinampas, floating islands made out of trees and mud that were used to grow food – for navigational and transportation purposes. Though the lake and much of the canal system have been drained over the years to make way for a growing population, more than 183km of canals remain in the Xochimilco borough, and 165 hectares of land and water are located in the protected area of the Xochimilco Ecological Park.
But rather than axolotls, visitors today are likely to see numerous migratory bird species and revellers on boats in the canals. The area has become heavily touristed and is best known as a place to go for a ride in colourful wooden boats called trajineras, where smaller boats come over full of mariachis, or to sell beer and refreshments.
Environmental threats
As trajineras are motorless boats, they are not thought to negatively impact the axolotls. However, the chinampas are not connected to the city’s sewage system, so waste often winds up in the canals. Other threats to the amphibians include the quick growth of non-native, ornamental aquatic plants, and pollution from industrial fertilisers, as well as invasive species such as carp and tilapia, which were introduced by the government in the 1970s to supply food to the formerly rural area. The latter idea was well-intentioned, Servín Zamora said, but not well thought out, as the carp and tilapia feast on young axolotls.
“The problems that Xochimilco faces are not just environmental, but social as well,” Servín Zamora said. “People do not have enough income from their chinampas or ecotourism, so they tend to build their homes there [on their chinampa land, which is an affordable option as they already own the property] and for that reason urbanization has grown so much in those areas. Unfortunately, all the drainage from those homes goes directly into the canals, and that has caused tremendous pollution.”
In 2017, the National Autonomous University of Mexico (UNAM) did a study monitoring the canals. While the results are still under review, it was shown that the water pollution is very serious in Xochimilco’s rapidly growing urban zones. Servín Zamora said there is hope of recuperating spaces still devoted to agriculture and therefore less likely to be tainted by pollution caused by overpopulation. “If we work hard with education, research and working directly in the area, we can rescue it, even if it’s just one part.” Still, the study found just one axolotl living in the wild in Xochimilco.
Saving the axolotl
Today, most axolotls live in captivity. Yanin Carbajal is the co-founder of Casa del Axolotl, a museum and aquarium dedicated to educating the public on axolotls, located in the town of Chignahuapan in Puebla. Her project started years ago with breeding tanks at her family’s ranch in the foothills of the Sierra Madre Oriental mountains. The museum space located in town opened last year, featuring 15 to 20 axolotls of four different species.
Carbajal said she was motivated to care for axolotls because of their strong link to Mexico’s pre-Columbian history, their important implications for human health, and the goal to preserve the species and improve their habitats. However, she cautions potential pet owners that raising axolotls is no simple feat. While keeping them as pets around the world is legal, in Mexico it’s only legal to obtain them from a nursery accredited by the secretary of environment.
“Ignorance is a big problem, with people taking them from the wild and keeping them as pets in some cases or selling them,” Carbajal said. “If people are able to breed them, well that is a positive. But if not, then that is not helping the species. As they live in still water lakes and lagoons, the temperatures tend not to fluctuate as quickly as they can in captivity [making captivity a serious undertaking].”
Mexico City has a few places where captive axolotls can be seen today, including Chapultepec Zoo, Zoológico Los Coyotes and the headquarters of tour operators Axolotitlán and Umbral Axochiatl, both in Xochimilco.
Pamela Valencia is the founder of Axolotitlán, a Mexico City-based operator that aims to educate locals and travellers on Xochimilco’s delicate ecosystem and the need to support axolotls, through tours with a cooperative of local chinamperos (chinampa farmers) in the ecological park.

The axolotl is a secret to save our city, our country and probably the world

“The axolotl is a theme in Mexico that has to do with politics, society, the use of resources, environmental and systemized education,” Valencia said on a warm afternoon at her axolotl refuge, where visitors can come to learn about the axolotls. “It’s a topic that touches on all the rubrics of society in one way or another. We believe that the axolotl is a secret to save our city, our country and probably the world. It’s an incredibly important animal that can inspire people to stop doing things [such as polluting] that we’ve been doing for a long time as a society, and to do better in many ways.”
Dionisio Eslava, president of Umbral Axochiatl, which works with Axolotitlán to organise tours in his native Xochimilco so that visitors can better understand the natural side of Xochimilco, said that closing the gap geographically, culturally and socioeconomically between central Mexico City folk and the farmers in the south is one way to help clean up the zone, and thus help the axolotls return to the area.
“Ecosystems are a type of security, not only for food but also water, oxygen and as an ally for facing climate change,” he said. “The big cities should support our ecosystems by visiting us and accompanying us in this treasure that is a great inheritance of all of humanity.”
Not only can this small and often overlooked animal guide us in protecting the planet, but it potentially holds the key to unlocking certain scientific mysteries.
Frankie lived to be eight years old – though captive axolotls can live 12 years or more – dying of natural causes at Chapultepec Zoo in 2010. Servín Zamora holds a special place for him in her heart because he was one of the first axolotls she ever worked with and she learned quite a lot from him – hopefully, the rest of the world will, too.