FunNature & AnimalSome reptiles essentially do not age

Some reptiles essentially do not age

Aging has been extensively studied, especially in humans, and also in mammals and birds. The rate of aging of these animals is relatively easy to predict, knowing the phylogeny data, that is, their evolutionary ancestry and their body size.

In other animals, however, there is a gap in knowledge in this regard. It is true that we know of cases of very long-lived cold-blooded animals, such as Jonathan , a male giant tortoise from the Seychelles , brought to the island of Saint Helena in 1882, at the age of 50. Today he is still alive and holds the title of the oldest known living vertebrate in the world, at 190 years of age .

However, most of the available data on the longevity of these animals is based on anecdotal evidence and in many cases, obtained from captive animals, which tend to live longer. Finding more rigorous and well-cohesive scientific information on the aging of non-avian reptiles and amphibians was, until now, a very complex task.

One study to analyze them all

This was the starting problem that motivated a group of 114 researchers from around the world to carry out a massive investigation, on a total of 107 populations of 77 different species of amphibians and non-avian reptiles , and whose results have recently been published in the prestigious Science magazine.

The scientists analyzed four different factors to see how much they contributed to the rate of aging: thermoregulation , that is, the ability to maintain or not maintain body temperature; the ambient temperature in which they live; the protective traits they have; and the pace of life they present.

A team from the National Museum of Natural Sciences (MNCN–CSIC) has participated in the study, led by the researcher Íñigo Martínez-Solano, who has provided highly relevant data on populations of gallipato, spadefoot toad, natterjack toad, common frog and tree frog. from San Antonio, which they have been collecting in the Sierra de Guadarrama for more than a decade.

The variation of the rate of aging

Even taking into account these variables of phylogeny and size, the researchers found that ectotherms —cold-blooded animals whose body temperature depends on the temperature of the environment—have much greater variation in the rate of aging than endotherms —warm-blooded animals capable of aging. to regulate their own temperature: birds and mammals.

Regarding longevity , calculated based on the age at which 95% of the reproductive individuals die, among the cold-blooded animals they found animals that live less than a year, and others that can reach up to 137 years.

In all the major groups studied: frogs, salamanders, lizards, crocodiles, tuatara, and turtles, the researchers found species with negligible aging rates, including “essentially non-aging” species.

The researchers call ‘insignificant aging’ the constant maintenance of the mortality rate throughout life, once the reproductive age is reached, but regardless of age. On the average of humanity, the probability of a person dying at 20 years of age is a hundred times less than the probability of dying at 80. However, the probability of a giant tortoise dying at 10 years of age is the same than dying at 100 .

Among the direct results of the study, they found that turtles, crocodiles, salamanders, and tuatara have a very low rate of aging relative to their size; although there are reptiles and amphibians that age extraordinarily fast.

The slower they live, the longer they live

One of the hypotheses prior to this study is that the rate of aging in ectotherms was directly related to the metabolic rate; a slower metabolism, greater longevity.

This study rules out this hypothesis and reveals that aging rates in ectothermic animals decrease in those species with a slower pace of life . In addition, according to their data, the presence of protective or defensive features , such as having a shell, more or less thick scaly armor, poison or spines, are also associated with slower aging .

The findings of this team may represent an advance in the design of conservation strategies for reptiles and amphibians , many of which are in danger of extinction. In addition, according to the authors of this work, the evolutionary study of aging can help to better understand aging in humans.

References:

Reinke, BA et al. 2022. Diverse aging rates in ectothermic tetrapods provide insights for the evolution of aging and longevity. Science, 376(6600), 1459-1466. DOI: 10.1126/science.abm0151

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