Scientists studied the genome and epigenome of Jonathan, an Aldabra tortoise estimated to be about 194 years old, and found genetic features that may be linked to longevity.
Researchers compared his genetic data with that of four other tortoises. They found 287 gene variants unique to Jonathan. Some are associated with DNA repair and tumor suppression. The animal also has extra copies of a gene encoding a protein that helps the body identify aging and cancerous cells.
An analysis of the epigenome, chemical markers that influence gene activity, found lower methylation entropy in several DNA regions linked to longevity than in the other tortoises studied. The exception was a five-year-old specimen. The scientists also noted changes in pathways associated with mitochondrial function, insulin regulation and telomeres.
Jonathan was brought to St Helena as an adult in 1882. To collect biological material, researchers waited until he opened his mouth and took a sample from beneath his tongue. Blood collection on the island is restricted because of infection risks. The authors stress that studying one animal does not prove what caused its longevity. Genetics, a tropical environment, diet and veterinary care may all have played a role. Veterinarian Joe Hollins says the tortoise is almost blind because of cataracts but still has a strong appetite and remains beloved by island residents.