Friday, December 09, 2022

Secrets of aging revealed in largest study on longevity, aging in reptiles and amphibians

At 190 years old, Jonathan the Seychelles giant tortoise recently made news for being “the world’s oldest living land animal”. While there is anecdotal evidence that some species of tortoiseshell and other ectotherms – or ‘cold-blooded’ animals – are long-lived, the evidence is spotty and mostly animals living in zoos or some individuals living in the wild. are focused on. , Now, an international team of 114 scientists led by Penn State and Northeastern Illinois University has conducted the most comprehensive study of aging and longevity ever, involving data collected in the wild from 107 populations of 77 species of reptiles and amphibians around the world. reports.

In many of their findings, which they report today (June 23) in the journal Science, the researchers document for the first time that turtles, crocodiles and salamanders have particularly low aging rates and extended lifespans for their size. The team also found that protective phenotypes, such as the hard shells of most turtle species, contribute to slower aging, and in some cases ‘negligible aging’ – or even a lack of biological aging.

David Miller, senior author and associate professor of wildlife population ecology, said: “Anecdotal evidence exists that some reptiles and amphibians age more slowly, but so far no one has studied this extensively in many species in the wild. not done.” , Penn State. “If we can understand what allows some 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.”

In their study, the researchers applied comparative phylogenetic methods – which enable the investigation of the evolution of organisms – to characterize data – in which animals are captured, tagged, released back into the wild. is and is seen. Their goal was to analyze variation in ectotherm aging and longevity in the wild compared to endotherms (warm-blooded animals) and to explore previous hypotheses related to aging – including body temperature regulation and the presence or absence of protective physical traits. was involved.

Miller explained that the ‘thermoregulatory mode hypothesis’ suggests that ectotherms – because they require outside temperature to regulate their body temperature and, therefore, are often less metabolized – more slowly than endotherms. Age, which generates its own heat internally and has a high metabolism.

“People think, for example, that rats age quickly because they have a higher metabolism, while turtles age slower because they have a lower metabolism,” Miller said.

However, the team’s findings show that the aging rate and lifespan of ectotherms are both above and below the known aging rates for endotherms of similar size, suggesting that the way an animal lives on its own. What controls temperature – cold blooded versus warm blooded – is not necessarily an indication of its aging rate or lifespan.

“We did not find support for the idea that a lower metabolic rate means that ectotherm aging is slower,” Miller said. “That relationship was only true for turtles, which suggests that turtles are unique among ectotherms.”

The protective phenotypes hypothesis suggests that animals with physical or chemical traits that provide protection – such as armor, spines, shells or venom – have slower aging and greater longevity. The team documented that these protective traits, in fact, enable animals to age more slowly and, in terms of physiological safety, live longer for their size without the protective phenotype.

“It may be that their altered morphology with hard shells provides protection and has contributed to the evolution of their life histories, which include negligible aging – or lack of demographic aging – and exceptional longevity,” says Anne Bronikowski, Co-senior author and professor of integrative biology, Michigan State.

Beth Rinke, first author and assistant professor of biology at Northeastern Illinois University, further explained, “These various protective mechanisms may reduce the mortality of animals because they are not being eaten by other animals. Thus, their longer life expectancy.” is likely to live.

Interestingly, the team observed negligible aging in at least one species in each of the ectotherm groups, which include frogs and toads, crocodiles and turtles.

“It sounds dramatic to say that they don’t age at all, but basically their chances of dying don’t change with age,” Rinke said.

Miller said, “Negligible aging means that if an animal has a 1% chance of dying at 10 years old, if it is alive at 100 years old, its probability of dying is still 1% (1. In contrast, in the US among adult females, the risk of dying in one year is 1 in 2,500 by age 10 and 1 in 24 by age 80. When a species exhibits negligible aging (decline), So old age does not come.”

Rinke noted that the team’s novel study was only possible because a large number of collaborators from around the world studied a wide variety of species.

“Being able to bring together these authors who have put in years and years of work studying their individual species has made it possible for us to obtain these more reliable estimates of aging rates and longevity Which are based on population data rather than just individual animals,” he said.

“Understanding the comparative landscape of aging in animals may reveal resilient traits that may prove to be worthy targets for biomedical studies related to human aging,” Bronikowski said.

For a list of authors and their affiliations, please see the manuscript published in Science.

The National Institutes of Health supported this research.

(1) US Social Security Actuarial Life Table. Accessed June 1, 2022

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