Comprehensive Study of Reptiles and Amphibians Provides Fresh Insights on Aging and Longevity

Man has for long yearned for the secrets of being “forever young.” New research, the most comprehensive of its kind, now appears to have unlocked secrets that could help people age slowly and enjoy longer lifespans.

A Turtle

A Turtle

There is anecdotal evidence that some cold-blooded animals do not age very fast. A good example is Jonathan the Seychelles giant tortoise that made the news of late for turning 190.

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But there has been nothing dependable enough to back up available anecdotal evidence. This is partly because the focus has mainly been on animals in zoos or a few out in the wild.

In this new study, researchers used data collected globally from 107 wild populations of reptiles and amphibians. The animals belonged to 77 different species. This, therefore, is the most comprehensive inquiry on aging and longevity in these groups of animals yet.

For the first time, scientists found that turtles, crocodilians, and salamanders boast unusually low rates of aging and long lifespans for animals of their sizes. They also observed that protective phenotypes, for example, hard shells, play a part in their slower or even “negligible” aging.

Findings from this study appeared in Science. The research was carried out by a 114-scientist team led by researchers from Pennsylvania State University and Northeastern Illinois University.

Thermoregulatory hypothesis

Researchers in this study set out to examine variation in aging and longevity among ectotherms or cold-blooded animals in the wild, compared to endotherms or warm-blooded animals. They were interested in probing existing aging-related hypotheses, including body temperature regulation and the role of protective features.

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The “thermoregulatory mode hypothesis” proposes that ectotherms commonly have slower metabolisms and, so, age slowly because they draw on external temperatures to adjust their body temperatures, explained senior study author David Miller. Endotherms, on the other hand, age faster because they produce their heat and, therefore, have higher metabolisms.

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

Using comparative phylogenetic methods, the research team found this to not be the case. The aging rates and lifespans of cold-blooded animals vary significantly from those of warm-blooded counterparts of similar sizes. This implies that the manner of body heat regulation has little or no impact.

Protective phenotypes

The scientists found that the “protective phenotype hypothesis” may better explain why some ectotherms live for quite long. This proposes that animals with protective features (physical or chemical), including shells, spines, or venoms, age more slowly and have longer lifespans.

Turtles provide the most convincing evidence to support this theory, according to researchers.

An interesting finding by the team was that a minimum of one species in every ectotherm group showed negligible aging. Their biological aging was as slow as almost getting to a total halt. These species’ chances of dying remain unchanged once they are over and done with reproduction, researchers said.

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“Negligible aging means that if an animal’s chance of dying in a year is 1% at age 10, if it is alive at 100 years, [its] chance of dying is still 1%,” explained Miller, an associate professor of wildlife population ecology at Penn State. “By contrast, in adult females in the U.S., the risk of dying in 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 just doesn’t happen.”

Miller noted that scientists can better grasp human aging if they can figure out what factors make certain animals have slower aging. This knowledge can also guide the protection of reptiles and amphibians, a good number of which are endangered or threatened.

References

Diverse aging rates in ectothermic tetrapods provide insights for the evolution of aging and longevity

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