Rodrigo Cruz for The New York Times
MEXICO CITY ? Aztec legend has it that the first axolotl, the feathery-gilled salamander that once swarmed through the ancient lakes of this city, was a god who changed form to elude sacrifice.
But what remains of its habitat today ? a polluted network of canals choked with hungry fish imported from another continent ? may prove to be an inescapable threat.
?They are about to go extinct,? said Sandra Balderas Arias, a biologist at the National Autonomous University of Mexico working to conserve axolotls in the wild.
The loss of this salamander in its habitat would extinguish one of the few natural links Mexicans still have with the city that the Aztecs built on islands in a network of vast mountain lakes. Its extinction in the wild could also erase clues for scientists studying its mystifying traits.
Despite their precarious future in freshwater, axolotls (pronounced axo-LO-tuhls) have long flourished in aquariums. They have been bred successfully behind glass over the past century, raised as exotic pets or as laboratory specimens for scientists investigating their extraordinary ability to regrow a severed limb or tail.
The Mexican axolotl is an odd-looking salamander with a flat head and spiked feet, unusual because it often spends its entire life in the so-called larval stage, like a tadpole, without ever moving to land. ?It grows and grows in the same shape, and has the capacity to reproduce,? said the biologist Armando Tovar Garza. ?We don?t really know why it doesn?t change.?
Its gaze seems to captivate as its gills slowly beat. In Julio Cort?zar?s short story ?Axolotl,? the narrator is transfixed ? ?I stayed watching them for an hour and left, unable to think of anything else? ? and experiences his own metamorphosis.
The Aztecs and their descendants consumed axolotls as part of their diet, and the amphibians are still stirred into a syrup as a folk remedy for respiratory ailments.
But in their only home, the canals of Xochimilco in the far south of the city, the axolotls? decline has been precipitous. For every 60 of them counted in 1998, researchers could find only one a decade later, according to Luis Zambrano, another biologist at the National Autonomous University of Mexico.
Gliding on a flat-bottomed boat through the canals where the Aztecs once farmed floating gardens, but where cinder block houses now dump their waste and students toss their beer cans during parties, Mr. Tovar described the threats. ?The axolotl is suffering on two fronts,? he said, as pounding music and the smell of sewage filled the air. ?One is the water quality. It?s not improving.?
Then, as dimples appeared on the still surface of the canal, like raindrops before a deluge, another researcher leaned over and the axolotl?s second challenge became evident. ?See how the water is moving? All of those circles?? asked the researcher, Leonardo Sastre Baez, who monitors fishing. ?Those are the tilapias.?
That resilient fish was introduced over 20 years ago, along with carp, in an effort to support Xochimilco?s fishermen. ?The government thought, ?If people can?t work, at least they can eat,??? Mr. Sastre said. But the tilapias reproduce faster than they can be caught, and they feed voraciously on the plants where the axolotls lay their eggs.
Mexicans? taste for axolotls has endured, generating some strong reactions from Europeans over the years. The naturalist and explorer Alexander von Humboldt wrote in the 19th century that the Mexicans he observed lived ?in great want, compelled to feed on roots of aquatic plants, insects and a problematical reptile called axolotl.?
Others would disagree with the interpretation.
?Have you ever eaten frogs?? asked Roberto Altamirano, president of the fishermen?s association, who ate axolotls as a child and is now working to save them. ?Well, that?s what it tastes like. Somewhere between fish and chicken.?
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