The people of Mexico City recently chose it as their official emoji. Mendez-Rosas, the farmer, says that fishermen used to cast a net and catch 40 at a time. Now, standing by the side of a canal and beckoning us closer, he points to the last place he saw an axolotl wriggling in the mud…more than a year ago.
Their population density in these wetlands has nosedived from an estimated 2, salamanders per square mile in to less than 14 per square mile in , the year of the last census.
No one knows how many are left now. In Xochimilco, as in many other places, humans have pressed heavily against an ecosystem, imperiling plucky, charismatic creatures. Here, our slimy protagonist is beset on all sides. Second, some farmers have introduced invasive carp and tilapia, which gobble up axolotl eggs and compete with adults for food.
And third, pollution and sewage have reduced the water quality. But like all good stories, the quest to save the axolotl is more than it seems. Set in crowded Mexico City, it is a microcosm of conservation in the 21 st century. For well over a century, the salamanders have been raised in laboratories and kept as pets across the globe. The future of this salamander will be determined not by which plot of land we chose to preserve, but by how we answer a deeper question: What do we lose if Xochimilco loses its axolotls?
I first caught the axolotl bug this past summer, when a friend went on a few dates with a grad student who kept some in a genetics lab. Once I started looking, they turned up everywhere.
I saw them preserved in jars in the herpetology collection at Harvard University and others alive in a developmental biology lab upstairs. I even met a pet axolotl owned by a toxicologist in Japan. In the summer of , while the Union and the Confederacy were busy slugging it out at Vicksburg, France invaded Mexico City to collect on unpaid debts.
Hot on their heels, naturalists and biologists followed, as often happened with Enlightenment imperialists. In conquered Mexico, the French went searching for archeological discoveries to match the Rosetta stone.
Perhaps they could find another mystical object with the power to unlock vast recesses of time, to illuminate hidden relationships.
They did—only it was biological, not archeological. He bred them and shared their progeny with international colleagues. Lab axolotls have been going strong ever since. Instead of losing their gills and crawling onto land like other salamanders, axolotls happily spend their entire lives underwater.
They even breed in that form. But in , something even weirder happened. The concordance is just too perfect: their namesake god Xolotl, twin brother of Quetzalcoatl, had the power to shapeshift. Either way, this hidden extra rung in axolotl development helped early 20 th century scientists discover thyroid hormones, which can reliably induce the change.
The Kentucky salamanders are different from wild ones in some key respects, he told me on the phone. For one, this population is nicer. Axolotls may also offer insight to the genetic controls that regulate the switch in life for processes like puberty.
With the race against the clock growing ever pressing, the axolotl conservation efforts ramped up in the early s with a proposed captive breeding and species reintroduction project. Thus, the team developed an action plan in to raise the profile of the axolotl in the local community through education programs, workshops, and public meetings.
They focused on integrating the axolotl into the tourism in the community. Local businesses like La Casita del Axolotl breed axolotls for sale and conduct tours with their guests and clients. The local community was always essential for the axolotl conservation efforts. The difficult method of collecting axolotls—searching for subtle bubbles and casting the net just right—that is needed for censuses is hard to teach, but it is a skill that is passed down through generations of local fishermen.
Locals distrust scientists, who have historically exploited the community for data in the past without coming back or paying them sufficiently. Zambrano approached the relationship differently. He knew the community had all the knowledge he needed, so he offered his data collecting skills and credibility as a way for them to have their voices heard—and to help their livelihoods.
These efforts have scaled up in recent years as Zambrano involves local farmers in the process. The productive and sustainable agricultural system does not use chemical pesticides—they have even experimented with grinding up invasive tilapia for fertilizer—and creates a semi-permeable barrier to provide refuge for the axolotl with clean, filtered water.
It may not be enough. Zambrano is hopeful. He has seen a steady increase in interest in the axolotl, which he hopes to leverage into local government action.
The first step, he says, is to save Xochimilco. Future of Conservation A Smithsonian magazine special report. Whereas such a wound in humans gets covered with skin tissue, axolotls transform nearby cells into stem cells and recruit others from farther away to gather near the injury. There, the cells begin forming bones, skin and veins in almost the same way as when the animal was developing inside the egg. Each tissue contributes its own stem cells to the effort.
Adult mice and humans can regenerate digit tips , although humans lose this ability with age, suggesting that regenerative abilities could be reawakened in mammals. His studies are not focused on rebuilding limbs, but on curing paralysis, growing healthy organs and even reversing ageing by repairing damaged and worn-out tissues. By the time that day comes, however, the wild axolotl may be gone.
But they are so inbred. Their high level of inbreeding is partly a result of the bizarre historical path captive axolotls have taken. Most laboratory specimens trace their heritage back to a single group of 34 animals that were taken out of Xochimilco by a French-funded expedition in They sparked an axolotl-breeding craze across Europe by museums and naturalists. In , some of the animals travelled from a Polish laboratory back to North America, where they eventually became a breeding stock at the University of Buffalo, New York.
Here, scientists brought in a series of wild axolotls to mix up the gene pool and at one point even added in tiger salamanders Ambystoma tigrinum. The Buffalo population thrived and eventually moved to the University of Kentucky in Lexington, which is now the centre of global axolotl breeding.
This means that, in addition to being inbred, almost all of the axolotls in labs and aquariums today are actually part tiger salamander. Voss says that axolotl research today is expanding throughout the world, thanks to modern genetics and stem-cell research. In , he and his group published an initial assembly of the axolotl genome, a Herculean task given its large size, estimated to be about 32 billion bases.
Scientists in several centres continue to work on completing the picture. Scientists worry that if a new infectious disease were to race around labs worldwide, it might force them to abandon the axolotl, potentially setting research back by years.
For example, they often have too many fingers. On the side, he breeds his own wild axolotls to sell to labs and pet distributors. He is standing over a salamander tank on a traditional Xochimilco farm plot, or chinampa , that is used as an educational facility for tourists. These animals, and the others he sells, were bred from a group of 32 pulled out of the water not far from the plot.
In Mexico, the axolotl is a prized pet and a source of national pride. Zambrano guesses that during his last survey, in , there were fewer than 1, in total, and perhaps fewer than Zambrano says that to save the wild axolotl, policymakers must address its two primary threats.
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