Lizard Popsicles, anyone? – new York Times


Stephen Hallow was surveying plants and wildlife on the high plateaus around San Miguel de Tucman, northwestern Argentina in the 1970s when he first encountered lizard popsicles.

Mountains around the city of Argentina climb steeply from 13,000 to 16,400 feet, increasing the crowds of ecological trails in a relatively small area. The plateau at the top can be hot in the afternoon, but can quickly drop below freezing at night – not exactly the kind of place you’d expect to find a lizard.

However, Senior Advisor to the New Zealand Ministry for Primary Industries, Dr. Halloy caught some and kept them in a box outside his camp overnight. “When I opened the box the next morning they were hard like wood – you couldn’t bend them,” Dr. Charles recently recalled. “They were absolutely dead.”

But after the sun rose, the lizard began to thaw and soon ran around the box as usual.

“Clearly I found that very surprising,” Dr. Hallow said.

In the 1990s, biologist Robert Espinoza of California State University, Northridge, wrote to Drs. Heard this story from Halloy, and he has been studying lizard popsicles ever since. The lizard belongs to the genus Leolamus, and Drs. Research by Espinoza and his colleagues showed that lizards are undeniably the quietest on the planet. While tropical lizards such as iguana fall from trees when they are cold, leolamus can supercool their bodies, tolerate cold, and live in the south and at higher elevations than any other lizard species.

“They are the actual record holders,” Dr. Espinoza said.

The Leolemus species has been found on the island of Tierra del Fuego at the southern end of the Americas, and a researcher has even heard stories of walking on a glacier Perito Moreno from Paragon. Most of the Leoliums are found in Argentina and Chile, although some are found as far north as Peru. With over 272 documented species, Leolamus is the second largest genus among all mammals, birds, and reptiles, after only the anvils, another type of lizard.

Dr. Espinoza is still investigating how these lizards survive such a cold climate. In one experiment, his team fitted models of hollow copper-made lizards with a temperature logger, and placed them in an area at 13,369 feet in the province of Salta. The model recorded temperatures as low as 11.2 degrees Fahrenheit and 15.8 Fahrenheit on the surface. (The lizard usually spends the night under burden.)

The team then tested the cold adaptation of six species from different heights. They found that some cooling can remain as low as 21.2 degrees Fahrenheit, although Drs. Espinoza suspects that wild lizards can withstand cold temperatures. Leoleymus hussaihusiscus, dr. The species that Helloy initially encountered was the most numerous of the species Drs. It lives 1,640 feet higher than Espinoza, which is currently a colder region.

Dr. Halloy noted in a 1989 publication that Leolamus Hiahuasicus could survive the cold at 14 degrees Fahrenheit, but only when at an altitude of 13,944 feet; The lizard died when it was cooled to 26.6 ° F in a test conducted at 1,476 feet.

Dr. Espinoza and his co-authors found that liolemus lizards have adapted abilities to cope with cold through three mechanisms. Some lizards go underground and survive extreme cold. Others use a process of supercooling; By remaining completely stable, they can allow their bodies to fall below freezing without actually freezing solid. Finally, some can tolerate full-body cold for a short time. Dr. Espinoza stated that some Liolamus species are likely derived from the use of more than one mechanism depending on the conditions.

The whole-body freezing strategy is probably similar to that of North American wood frogs thanks to frozen antifreeze-like glucose solutions in winter that protect cells; Dr. Espinoza still needs to investigate this hypothesis. The southernmost landmass in the world, marked landmark of Darwin, another Argentine lizard, whose dau. Espinoza has studied, most likely adopting a supercoiling strategy.

The liolemus lizards can withstand such cold temperatures and the high altitude may also explain why there are so many reasons for lizards. While only 50 were described about science when in the late 1970s Dr. Halloy worked on them, now there are 272 species.

Dr. Espinoza and others have discovered several species, and his occasional co-author Fernando Lobo, a zoologist at the National University of Salta in Argentina, has discovered 30 or more species of Lyolemus and his close cousin, the genus Fimturus.. In one case, Drs. Lobo discovered a species under his tents in a cloudy, frozen season in the Santa Cruz province of Santa Cruz near the Chilean border.

Dr. “They didn’t look like the others,” said Lobo. “We suspected they were new. We have received that enthusiasm dozens of times over these 25 years. “

At the current rate of discovery, leolamus will become the gene with the highest number of living mammals, reptiles and birds in the coming years.

Dr. Espinoza stated that a large number of the Leolemus species may be related to the mountainous region where they live. The Andes are relatively young – about the same evolutionary age as the lizard. They believe that as the Andes pushed out of the Earth’s crust, the genus spread to innumerable ecological traces that eventually resulted in new species.

Dr. “The Andes is a species pump making all these new variants,” Espinoza said.

Most lizards are similar in size, but they differ greatly in color and even diet and birth strategies. Dr. Lobo related a story about an expedition in Jujuy Province, Argentina. During her work, a local woman appeared in the mountains from a small sheep- and lama-shepherd village.

Dr. Lobo said, “She told us very clearly which species was the Indian name, and said ‘she lays an egg and she gives birth.”

Dr. Espinoza said that half the lizards give birth to live young, probably because laying eggs in cold temperatures is probably not a recipe for success for some species. In 2016, he also described a new species Leolemus Parthenos, in which females breed from a male without fertilization, through virgin birth.

Researcher Melissa Olave of Argentina’s National Scientific and Technical Research Council, who heard about lizards on Perito Moreno, recently conducted a study, which suggested that the rise of the Andes may not be the only factor driving leolamus development and diversity is. The extinction rate is very low relative to other lizards of the species Leolamus. Their diversity in habitat use, generalist approaches to diet – some species are herbivores while others are omnivores or carnivores – and various forms of reproduction may be important to explain the richness and survival of the Leolamus species. She said that being a generalist is generally considered beneficial, as it is easy to find suitable habitat in the highly diverse landscapes of the southern cone of South America.

In other words, the high diversity of Leolamus may be the product of lower deletion rates than habitats.

Dr. Espinoza agreed that species persistence over time could be an important factor in species richness, but he also believed that alone could not explain diversity.

In any case, Drs. Olave has shared the common sense of astonishing many researchers working with those lizards.

“The Leolemus species has an extraordinary ability to survive through time,” she said.

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