Environment
Ronaldo Schemidt / AFP / Getty Images
MEXICO CITY — Dark, slimy and mysterious, the creature moves with a sluggishness reminiscent of prehistoric animals. But when it pulls in its legs, it can swim fast like a fish. If it loses a limb, it can grow it back.
The axolotl (pronounced ASH-oh-LOH-tuhl), as it was called by the Aztecs, is a fantastic amphibian that embodies the mysteries of Mexico’s ancient world. Revered for centuries, this Mexican wonder is under threat.
The Mexican salamander is found only in its original habitat, Xochimilco. The area contains the last remnants of a system of lakes and canals upon which the Aztec capital thrived. But Xochimilco is now a UNESCO World Heritage site at risk of being swallowed by massive urbanization and pollution in this sprawling capital of 22 million people.
The Aztecs venerated the axolotl as a god, the twin brother of their most important deity, the feathered serpent Quetzalcoatl. Axolotls have been depicted throughout the ages in Mexico, from archaeological sites to modern art. In Diego Rivera’s mural “Water, Origin of Life” (1951), an axolotl swims near a male figure’s genitals — symbolically at the center of creation.
Having the rare amphibian capacity to grow into adulthood without undergoing metamorphosis, the axolotl lives in an eternal adolescent stage. It can regenerate limbs and organs — even parts of its heart and brain — which makes it a valuable case study for scientists all over the world.
Randal Voss, a biologist at the University of Kentucky who’s leading the Salamander Genome Project, is trying to sequence the axolotl genome looking for possible applications for tissue, limb and spinal cord regeneration.
His research program receives nearly a million dollars a year from the National Institute of Health, the National Science Foundation and the Army. Understanding the axolotl's RNA sequence might save human lives and unlock secrets against aging.
“I wouldn’t work on this if I didn’t believe it could help save lives,” Voss said. "Axolotls are interesting beyond regeneration because they seem to cheat aging. They retain juvenile features, such as their skin and gills, until they die."
But these secrets for longevity and regenerative medicine won’t ever be unlocked if the axolotl continues on its path to extinction.
A recent study from the National Autonomous University of Mexico (UNAM) shows in 1998 there were 6,000 axolotls per square kilometer in Xochimilco. By 2008 that figure had plummeted to 100. And in 2014 researchers found less than one per square kilometer.
There are at least three major causes for its decline: urbanization, water pollution and the massive invasion of exotic predator fish like carp and tilapia, introduced by the Mexican government in the 1980s to help feed local communities. From the first few thousands they introduced, there are now an estimated 900 tons of fish in these canals.
“It’s an amazing amount. About 98 percent of the biomass in the water is made up of just these two fish, and they destroy everything,” said professor Luis Zambrano, an ecologist at UNAM who studies Mexican salamanders and the deterioration of their environment. “The government didn’t know what they were doing. They’ve altered the food chain and the whole ecosystem.”
Roberto Altamirano
fisherman
These aren’t the only threats. A lucrative black market tempts many poor fishermen to hunt axolotls in Xochimilco’s rich but murky waters.
“Buyers come and tell me, ‘I need 20 axolotls.’ Sure, I can get you that,” said Roberto Altamirano, who is proud to be one of the few remaining fishermen who still know the art of catching an axolotl in the wild.
While digging a pole into the muddy bottom to push forward his trajinera — the typical canoe residents use to navigate these waters — Altamirano said a buyer, typically a foreigner, would give him nearly $300 for each axolotl caught in the wild, enough to feed him and his family for two months.
These days, though, he and other fishermen and farmers are becoming more sensitive to the degradation of the area. Some now cooperate with ecologists clearing trash from the canals, rescuing the area's unique fields and repopulating the native flora and fauna.
Jesús Correa is one of them. He grew up in Xochimilco and runs Casita del Axolotl, a small ecotourism operation on a green chinampa, one of the floating islands typical of the area that were once dedicated to agriculture.
In his aquarium, he and his wife breed and care for about 350 little salamanders in small tanks. He draws the water from the canals and purifies it with plants to reduce contamination. On weekends he gives tours to curious tourists in which he explains the incredible nature of the axolotl and its challenges, in exchange for donations to support the breeding center.
Correa said his goal is twofold: “To help save the species and also bring back ancient traditions,” like the one to eat axolotl as a delicacy, as the Aztecs did, and use it as a natural folk medicine.
In the future, he hopes there will be enough axolotls to turn the breeding center into a profitable business.
“We would like to be able to sell it for scientific research, market it as a cure for breathing problems and to make the traditional local dishes that were typical in this area and went lost,” he said.
But the reality of such ecotourism operations is less idyllic than it appears. Correa can breed up to a thousand eggs from one pair of axolotls found in the wild, but neither selling them nor releasing them in the wild would help the species rebound. The offspring are all twins, with a similar genetic makeup. Reducing the genetic variability of the species makes it weaker.
Also, the bred axolotls are kept and fed in captivity and are not used to fending for themselves. “If you were to release them in these polluted canals, they would die for sure,” said Zambrano.
“Repopulating the canals with these samples is definitely not a good idea,” he said. “Not only will it not save the species — it will jeopardize it.”
In these tricky waters, the only solution then is to protect the endangered axolotl in its habitat, which is what the UNAM team is trying to do with the help of local farmers.
In a small tributary canal, the research group set up refuges with plants to purify the water and a few cages where the axolotl can live and reproduce without stress.
“Here they have to swim, hunt and fight for food, so they’re healthier and stronger than the animals who live in a tank or in a lab,” explained Armando Tovar, a biologist from the rescue project. In his hand he held a juvenile axolotl so dark it was camouflaged by the black mud found at the bottom of the canal.
“These are phenomenal animals who can even evolve genetically, and this is what we want for the conservation of the species,” he said. But even the strongest axolotls are under threat. Tovar said more than 200 axolotls were stolen from their underwater cages one recent night.
“Many fishermen are willing to steal axolotls from breeding centers because it’s too hard to find them in the wild these days,” said Altamirano. “There is no monitoring in Xochimilco. It’s a lawless land,” he admitted, showing an illegal fishing net that has holes so tight, even axolotl eggs wouldn’t pass through.
Meanwhile, the whole world heritage site is constantly threatened by growth. The latest project proposed by the government is a new airport that would draw traffic and unregulated construction through the area.
Zambrano believes the fate of the axolotl and of its native wetland are intertwined.
“If we lose Xochimilco, we lose the axolotl,” he said. “If we lose the axolotl, we’ll probably lose Xochimilco.”
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