Jonathan...a long-lived turtle may help understand the secrets of longevity

Genetic analysis has revealed potential secrets behind the longevity of Jonathan the giant tortoise, the oldest known land animal, who is believed to be 194 years old. These findings may help in the future to develop treatments to slow age-related cellular deterioration in humans.

Jonathan belongs to the Aldabra giant tortoise family, native to the Seychelles Islands in the Indian Ocean, but he spent most of his life on the island of St. Helena in the Atlantic Ocean. Giant tortoises usually live more than a century, but Jonathan, who is approaching 200 years old, represents an exception even among members of his species.

The long lifespan of giant turtles may be due to slow metabolic processes within their cells, which limits damage to cells and DNA, according to a study published in the journal Science Advances on Wednesday. The researchers examined Jonathan's genome and the mechanisms that control the activity of his genes, and discovered 287 genetic variants that may help protect his cells from damage.

Justin Gerlach, a researcher at the University of Cambridge and a participant in the study, said that Jonathan possesses genes that are effective in repairing DNA and reducing inflammation, and also retains the gene regulatory mechanisms that characterize younger animals. He added that these mechanisms begin to malfunction earlier in most animals, including humans, which may lead to health problems such as cancer.

Researchers still do not know whether these characteristics characterize Jonathan alone or giant turtles in general. For his part, João Pedro de Magalhaes, Head of the Department of Molecular Biology of Aging at the University of Birmingham, who was not involved in the study, said that understanding the causes of varying lifespans in organisms may open new horizons for understanding aging and longevity, and contribute to developing applications to improve human health.

A blueprint for resilience and resilience Jonathan's exact age is not known, but scientists estimate him to be about 194 years old, based on a photo taken of him in 1882 on the island of St. Helena, after he reached his full size. Since giant tortoises reach this size around the age of 50, they inferred his current age.

In 2022, December 4, 1832 was set as his official date of birth. Based on this estimate, the Governor of St. Helena set 2022 as Jonathan's official date of birth, December 4, 1832, a period when Abraham Lincoln, Charles Darwin, and Queen Victoria were all alive and well.

But researcher Justin Gerlach believes that it is more than 200 years old. It is believed that Jonathan was transferred to St. Helena in the nineteenth century, as a gift to a colonial official, after the giant tortoises were considered rare and intriguing creatures.

This spared him the fate of other turtles that ship crews held captive for months as a food source. Gerlach said that this cruel practice contributed to the extinction of one of the turtle species in Mauritius.

Jonathan weighs about 180 kilograms, is still active despite losing his sight due to cataracts, and is a tourist attraction in St. Helena. The researchers collected DNA samples by swabbing his mouth instead of drawing blood, to avoid infection due to his advanced age, but this method limited the accuracy of genetic sequence analysis.

By comparing its genome to younger turtles of its own species in the Seychelles, the researchers noted that its mitochondria, which are responsible for producing energy in cells, were in remarkably good condition. Stephen Clark, the study's lead author, said the team plans to analyze other turtles to see if these characteristics are common to their species.

He added that the results are consistent with data indicating the efficiency of mitochondria in some centenarians who are over 110 years old. Clark believes that Jonathan's study may help develop drugs that enhance mitochondrial health in humans, in preparation for testing them in clinical trials during the next year or two.

The need for more samples. Handan Melika Donertas, an assistant professor and researcher in the field of genomics at the Middle East Technical University in Turkey, who is not involved in the study, believes that analyzing Jonathan’s genome alone is not enough to determine the reasons for his long lifespan, pointing out the need to study more giant tortoises and other long-lived species to understand the genetic factors that may explain this phenomenon. Lynch, a professor in the Department of Biological Sciences at the University at Buffalo in New York, said Jonathan represents an ideal research model for studying genetic changes associated with longevity, which makes the study so important.

But he warned that some of the methods used may lead to false positive or negative results. Lynch explained to Ofoq News that the computer methods used to determine whether genetic mutations are beneficial or harmful are affected by assumptions related to the evolution of genes, and these assumptions, despite the prevalence of the model used, may lead to the classification of beneficial mutations as harmful, or vice versa.

Despite these limitations, Elenia Chiari, an assistant professor at the School of Medicine and Health Sciences at the University of Nottingham in the United Kingdom, believes that the study represents a valuable addition to the growing body of research indicating the ability of giant tortoises to live long and maintain good health, beyond the expectations associated with their lifespan.