It is completely normal for all living organisms to get older and then die. However, all organisms will not weaken and decline at the same rate.
Researchers from the University of Southern Denmark have found that many species of turtles and turtles can slow senescence considerably. They reported in their study, published in the journal Science, that these animals may exhibit an almost total absence of senescence in some cases when living under better conditions.
“Contrary to widespread theories of aging, we show that many species of turtles and tortoises have found a way to slow down or even completely switch off senescence,” said Rita da Silva, a biologist at the University of Southern Denmark. “This means that senescence is not inevitable for all organisms.”
The aging pattern in these Testudines is unlike what is seen in humans or other animals.
Growth after sexual maturity
According to some evolutionary theories of aging, senescence gets going after sexual maturity. Scientists consider it a result of the tradeoff between investing energy to the repair of cell and tissue damage and to reproduction for passing genes to the next generations.
The tradeoff means that the gradual weakening and deterioration of the body with age is inevitable. This is because an individual stops growing and starts experiencing senescence with energy devoted to reproduction after reaching sexual maturity. And this has been proven in several species, especially mammals and birds.
These evolutionary theories may, however, not apply in all cases as some animals continue growing after sexual maturity. This new study shows that turtles and tortoises are an exception.
Effect of better living conditions
In this research, the team focused on turtles and tortoises living in aquariums and zoos. This implies that the animals enjoyed better living conditions, compared to those in the wild.
Da Silva and her colleagues found that 75 percent of 52 species displayed very slow senescence. Compared to modern humans, 80 percent of the species showed slower senescence.
The researchers reported that the rate of senescence was as low as zero for Aldabra giant tortoise. This rate was even less than zero for the black marsh turtle, which means their risk of dying drops with age.
“We find that some of these species can reduce their rate of senescence in response to the improved living conditions in zoos and aquariums, compared to the wild,” said Dalia Conde, study co-author and an associate professor at the University of Southern Denmark’s Department of Biology.
Researchers think organisms, such as Testudines, have the ability to keep investing energy in the repair of cellular damages after sexual maturity. This helps them to keep the effects of senescence at bay.
Humans now enjoy longer lifespans in most cases, compared to the past. However, human and non-human primate studies have shown that better living conditions have little effect on aging. This makes the findings in turtles and tortoises interesting.
Researchers caution, however, that significantly reduced senescence does not imply that turtles and tortoises will not die. They will eventually die as a result of one of the “unavoidable” causes of death, such as illness.