What causes the longevity of 77 species of ectotherms?

The largest ever study of aging reptiles and amphibians has unveiled some of the secrets to long, cold-blooded lives.

The international research team, 114 strong, gathered data from 107 wild populations of 77 different species of ectotherms (cold-blooded creatures, or reptiles and amphibians).

Posted in Science, the study shows that ectotherms have a much more variable longevity and aging than birds and mammals.

“There is anecdotal evidence that some reptiles and amphibians age slowly and have long lifespans, but so far no one has really studied this on a large scale on many species in the wild,” says the author. Principal David Miller, Associate Professor of Wildlife Population Ecology at Penn State University, USA.

“If we can understand what causes certain animals to age more slowly, we can better understand aging in humans, and we can also inform conservation strategies for reptiles and amphibians, many of which are threatened or endangered. disappearance.”

The American researchers who led the study compiled data from more than 100 long-term studies on ectotherms, conducted around the world.

An Iberian tree frog (Hyla molleri). Credit: Iñigo Martínez-Solano

“It must be a huge effort to manage this number of authors and comments from everyone,” says co-author Professor Mike Gardner, a biodiversity and ecology researcher at Flinders University.

Gardner provided information on the longest survey of lizards in the Southern Hemisphere: A Sleeping Lizard (Tiliqua rugosa) investigation launched in 1983 by the late Professor Mike Bull. The study, now led by Gardner, is in its 40e year.

The compilation of information has yielded a wealth of new findings, challenging many previous assumptions about longevity in ectotherms.

One of these hypotheses is that the way an animal regulates its temperature is related to its lifespan.

Painted turtle swimming in the lake
A painted turtle (Chrysemys picta). Credit: Beth A. Reinke, Northeastern Illinois University

“We didn’t find support for the idea that a lower metabolic rate means ectotherms age more slowly,” says Miller.

“This relationship was only true for turtles, suggesting that turtles are unique among ectotherms.”

They did, however, find evidence to support the protective phenotype hypothesis, which suggests that animals with protective traits like armor or venom will live longer.

“It could be that their altered morphology with hard shells provided protection and contributed to the evolution of their life history, including negligible aging – or lack of demographic aging – and exceptional longevity,” explains the co-lead author, Professor Anne Bronikowski, researcher. in Integrative Biology at Michigan State University, USA.

Many animals in captivity have a different lifespan than those living in the wild. Gardner says that’s probably true for sleeping lizards — but their longevity makes it hard to tell.

Phylogenetic tree of animals
Supertree of all endothermic and ectothermic species included in this analysis. Branch lengths are not scaled. Red in the inner circle represents endotherms and blue represents ectotherms, as in all paper. Green bars are longevity estimates and orange bars are aging rates. Silhouettes from Phylopic.org. Credit: scientific journal

“I think lizards in captivity will last longer, but these things live so long that we probably don’t know of people who have had them for that long.”

The long-term study showed the vulnerability of sleeping lizards to medium- and long-term environmental changes, such as droughts caused by El Niño years. Like other long-term studies in the article, the ability to follow individual animals over a long period of time has provided data that shorter-term projects cannot answer.

“One of the things this article shows is the real value of these long-term studies,” says Gardner.

“It’s always hard to keep funding these things because you’re kind of dependent on these short-term cycles.

“When I took over this study, it was to a point where it was like, ‘well, is this really going to continue?’.”

Gardner took over the Sleeping Lizards investigation in 2017, after Bull’s untimely death. Current funding for the project expires at the end of this year, and Gardner is hoping for a grant that will extend it for another three years.

Two sleeping lizards under a tree
Sleeping lizards. Credit: Mike Gardner

“But I am indebted to these very short-term cycles.

“[These studies] are valuable because you have so much background information about it that you can ask really probing questions, which you just can’t ask in other systems because you don’t have that data from fundamental basis.

The survey of sleeping lizards is also accept donations from the public.



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