judith de george

Madrid

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All living organisms age and die. There is no way to escape death, but senescence, as biological aging is known, may not be an inescapable fate after all. Two studies published Thursday in the prestigious journal Science show that many tortoises that live exceptionally long lives – some of them exceeding 100 years – have found a way to slow down or even turn off age decline altogether. Researchers have discovered that these animals can stay young longer if their environmental conditions improve, something impossible for humans.

A team from the University of Southern Denmark studied 52 species of tortoises and tortoises that live in zoos and aquariums.

They found that their pattern of aging it does not resemble that of humans or other animals. In fact, most of them age extremely slowly -80% do so more slowly than humans-, and although it seems incredible, in some cases their senescence is insignificant. They include the Greek tortoise (Tortoise) and Hermann’s (T. hermanni), whose aging rates are indistinguishable from zero.

sexual maturity

Some evolutionary theories predict that senescence appears after sexual maturity as an exchange between the energy that an individual invests in repairing damage to their cells and tissues, and the energy that they invest in reproduction, so that their genes pass on to the next cells. generations.

This compensation implies, among other things, that, after reaching sexual maturity, individuals stop growing and begin to experience a gradual deterioration of bodily functions with age. In theory, such compensations are unavoidable, and therefore senescence is inevitable. In fact, this prediction has been confirmed for several species, particularly mammals and birds.

However, organisms that continue to grow after sexual maturity, such as turtles, are thought to have the potential to continue to invest in repair cell damage and, therefore, they are considered ideal candidates to reduce and even avoid the harmful effects of senescence.

they are not immortal

The researchers also discovered that some of these species may reduce their aging in response to better living conditions in zoos and aquariums, compared to nature. This does not happen to humans.

In the last century, human longevity has increased unprecedentedly. However, in primates, the improvement of living conditions does not greatly modify the rate of aging. Among these species, environmental changes primarily affect infant and juvenile mortality, as well as age-independent causes of death, such as predation or extreme conditions. “These species, including humans, cannot avoid senescence,” emphasizes Fernando Colchero, Professor of Mathematics and Computer Science at the University of Southern Denmark.

Of course, just because they age “does not mean that they are immortal; it just means that your risk of death does not increase with age, but is still greater than zero. In short, everyone will eventually die due to unavoidable causes of mortality, such as disease, “says Colchero.

calmly

In a second study, Beth Reinke and colleagues at Northeastern Illinois University in Chicago compared aging rates and lifespans for 77 species from 107 wild populations, including turtles, amphibians, snakes, and crocodiles. Ectotherm longevity (estimated as the number of years after first breeding when 95% of adults have died) ranged from 1 to 137 years. For comparison, primate longevity ranges from 4 to 84 years. The authors also found little evidence of aging in multiple species of turtles, in some salamanders, and in the tuatara (a reptile endemic to the islands off New Zealand). For these researchers, protective adaptations like bony shells and the relatively slow pace of life, in the case of turtles, help explain their insignificant aging.

Interestingly, and contrary to what happens with humans, males outlive females. However, when the females are larger than them, they have a longer life expectancy.

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