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Scientists discover species that don’t age

By on July 17, 2022 0

The research team also found that protective phenotypes, like the hard shells of most turtle species, can delay the aging process and, in some circumstances, even halt biological aging.

Largest Study of Its Kind Reveals Wild Turtles Age Slowly, Live Long, Discovers Several Species That Virtually Never Age

Jonathan, the 190-year-old Seychelles giant tortoise, recently made headlines for being “the world’s oldest living land animal”. Although there is anecdotal evidence that some species of turtles and other ectotherms, or “cold-blooded” creatures, are long-lived, this evidence is patchy and focuses mostly on animals kept in zoos or small numbers of individuals surviving in the wild. The largest study on aging and lifespan to date, conducted by an international team of 114 scientists and led by Penn State and Northeastern Illinois University, was recently published. It contains data collected in the wild from 107 populations of 77 different species of reptiles and amphibians.

Tortoise Chrysemys Picta

A photo of a painted turtle (Chrysemys picta), a common species of freshwater turtle in North America. Credit: Beth A. Reinke, Northeastern Illinois University

The researchers found several things, including for the first time, that salamanders, crocodilians, and turtles had extremely slow aging rates and extended lifespans for their sizes. They recently published their findings in the journal Science. The research team also found that protective phenotypes, such as the hard shells of the majority of turtle species, lead to slower aging and, in some circumstances, even “negligible aging”, or absence of biological aging.

“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,” said David Miller, lead author and associate professor of wildlife population ecology. , Penn State. “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.”

In their study, the researchers used mark-recapture data, in which animals are captured, tagged, released into the wild, and then monitored, in conjunction with comparative phylogenetic approaches, which study the evolution of organisms. . Their aim was to compare ectothermic aging and lifespan in nature to endotherms (warm-blooded animals) and to investigate previous hypotheses about aging, such as the mode of control of body temperature and the presence or l absence of protective physical characteristics.

Spotted Tufted Tufted

The face of a tuatara (Sphenodon punctatus). Credit: Sarah Lamar

Miller explained that the “thermoregulatory mode hypothesis” suggests that ectotherms – because they need external temperatures to regulate their body temperature and, therefore, often have lower metabolisms – age more slowly than endotherms, which internally generate their own heat and have higher metabolisms.

“People tend to think, for example, that mice age quickly because they have a high metabolism, while turtles age slowly because they have a low metabolism,” Miller said.

The team’s findings, however, reveal that the aging rates and lifespans of ectotherms vary well above and below known aging rates for similarly sized endotherms, suggesting that how a animal regulates its temperature – cold-blooded versus warm-blooded – is not necessarily indicative of its rate of aging or its lifespan.

“We didn’t find support for the idea that a lower metabolic rate means ectotherms age more slowly,” Miller said. “This relationship was only true for turtles, suggesting that turtles are unique among ectotherms.”

The protective phenotypes hypothesis suggests that animals with physical or chemical traits that confer protection—such as armor, spines, shells, or venom—have slower aging and greater longevity. The team documented that these protective traits actually allow animals to age more slowly and, in the case of physical protection, live much longer for their size than those without protective phenotypes.

“It could be that their altered morphology with hard shells provides protection and contributed to the evolution of their life histories, including negligible aging – or lack thereof – and exceptional longevity,” said Anne Bronikowski, co-lead author and professor of integrative biology, Michigan State.

Beth Reinke, first author and assistant professor of biology at Northeastern Illinois University, explained in more detail: “These various protective mechanisms can reduce animal mortality rates because they are not eaten by other animals. Thus, they are more likely to live longer, which puts pressure to age more slowly. We found the strongest support for the protective phenotype hypothesis in turtles. Again, this demonstrates that turtles, as a group, are unique. »

Interestingly, the team observed negligible aging in at least one species in each of the ectothermic groups, including frogs and toads, crocodilians and turtles.

Iberian tree frog

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

“It seems dramatic to say that they don’t age at all, but basically their probability of dying doesn’t change with age once they get past breeding,” Reinke said.

Miller added: “Negligible aging means that if an animal’s risk of dying in one year is 1% at age 10, if it is alive at 100, its risk of dying is still 1%. In contrast, among adult women in the United States, the risk of dying within a year is about 1 in 2,500 at age 10 and 1 in 24 at age 80. When a species exhibits negligible senescence (deterioration), aging simply does not occur. ”

Reinke noted that the team’s new study was only possible thanks to the contributions of a large number of collaborators around the world studying a wide variety of species.

“Being able to bring together these authors who have all done years and years of work to study their individual species is what allowed us to get these more reliable estimates of aging rate and longevity that are based on demographic data rather than on individual animals,” she says.

Bronikowski added, “Understanding the comparative landscape of aging in animals can reveal flexible traits that may prove valid targets for biomedical study related to human aging.”

Reference: “Various rates of aging in ectothermy tetrapods provide information on the evolution of aging and longevity” by Beth A. Reinke, Hugo Cayuela, Fredric J. Janzen, Jean-François Lemaître, Jean-Michel Gaillard, A. Michelle Lawing, John B. Iverson, Ditte G Christiansen, Iñigo Martínez-Solano, Gregorio Sánchez-Montes, Jorge Gutiérrez-Rodríguez, Francis L. Rose, Nicola Nelson, Susan Keall, Alain J. Crivelli, Theodoros Nazirides, Annegret Grimm-Seyfarth, Klaus Henle, Emiliano Mori, Gaëtan Guiller , Rebecca Homan, Anthony Olivier, Erin Muths, Blake R. Hossack, Xavier Bonnet, David S. Pilliod, Marieke Lettink, Tony Whitaker, Benedikt R. Schmidt, Michael G. Gardner, Marc Cheylan, Françoise Poitevin, Ana Golubović, Ljiljana Tomović , Dragan Arsovski, Richard A. Griffiths, Jan W. Arntzen, Jean-Pierre Baron, Jean-François Le Galliard, Thomas Tully, Luca Luiselli, Massimo Capula, Lorenzo Rugiero, Rebecca McCaffery, Lisa A. Eby, Venetia Briggs-Gonzalez, Frank Mazzotti, David Pearson, Brad A. Lambert, David M. Green, Nathalie Jrei dini, Claudio Angelini, Graham Pyke, Jean-Marc Thirion, Pierre Joly, Jean-Paul Léna, Anton D. Tucker, Col Limpus, Pauline Priol, Aurélien Besnard, Pauline Bernard, Kristin Stanford, Richard King, Justin Garwood, Jaime Bosch, Franco L. Souza, Jaime Bertoluci, Shirley Famelli, Kurt Grossenbacher, Omar Lenzi, Kathleen Matthews, Sylvain Boitaud, Deanna H. Olson, Tim S. Jessop, Graeme R. Gillespie, Jean Clobert, Murielle Richard, Andrés Valenzuela-Sánchez, Gary M. Fellers, Patrick M. Kleeman, Brian J. Halstead, Evan H. Campbell Grant, Phillip G. Byrne, Thierry Frétey, Bernard Le Garff, Pauline Levionnois, John C. Maerz, Julian Pichenot, Kurtuluş Olgun, Nazan Üzüm, Aziz Avcı, Claude Miaud, Johan Elmberg, Gregory P. Brown, Richard Shine, Nathan F. Bendik, Lisa O’Donnell, Courtney L. Davis, Michael J. Lannoo, Rochelle M. Stiles, Robert M. Cox, Aaron M. Reedy , Daniel A. Warner, Eric Bonnaire, Kristine Grayson, Roberto Ramos-Targarona, Eyup Baskale, David Muñoz, John Measey, F. André de Villi ers, Will Selman, Victor Ronget, Anne M. Bronikowski and David AW Miller, June 23, 2022, Science.
DOI: 10.1126/science.abm0151

The study was funded by the National Institutes of Health.