Tortoises can live for centuries in the wild thanks to a biological mechanism that allows them to quickly eliminate damaged cells.
On the island of St. Helena in the South Atlantic, there is a creature listed in the Guinness World Records as the “oldest terrestrial animal in the world” (187 years old in 2019). This is Jonathan, a giant tortoise of the Seychelles subspecies. He was born in 1832—meaning he was 80 years old when the Titanic sank in the North Atlantic—and he continues to thrive today.
Jonathan the giant tortoise is now the oldest living terrestrial animal. (Photo: AFP).
Jonathan is just one of many examples of long-lived tortoises around the world. Professor of marine biology Jordan Donini at Florida SouthWestern State University in the United States told Live Science that sea turtles can live from 50 to 100 years, while land tortoises can live over a century. In fact, scientists do not even know the exact upper limit of lifespan for many tortoise species simply because the researchers themselves do not live long enough to find out.
So why do tortoises live so long? According to Assistant Professor of Physiology Lori Neuman-Lee at Arkansas State University, the answer lies in their biological mechanisms.
The telomere sequence, or non-coding DNA strands that cap the ends of chromosomes, plays a crucial role in the lifespan of an organism. These structures help protect chromosomes during cell division. Over time, telomeres shorten or degrade, leading to a loss of their ability to protect chromosomes, which results in errors in DNA replication. Consequently, this can cause issues such as tumors and cell death.
Tortoises have a lower rate of telomere shortening compared to most other animal species. This means they have a better ability to withstand damage that may arise from DNA replication errors.
In a study published in the journal bioRxiv, scientists found that giant tortoises, including Jonathan’s Seychelles subspecies, have the ability to protect themselves from the long-term effects of cell damage. They do this by quickly eliminating damaged cells through a process known as apoptosis or programmed cell death.
Each time this process occurs, it causes oxidative stress or oxidative imbalance, a type of natural stress that occurs in living cells. As a result, tortoise cells quickly undergo apoptosis.
“We want to emphasize that controlled apoptosis is truly valuable because if an organism can quickly eliminate damaged cells, it can avoid health risks such as cancer,” Neuman-Lee stated.
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