A Greenland shark unintentionally captured in a fishing catch from the research vessel Pâmiut in southwest Greenland. | Julius Nielsen
Greenland sharks enjoy the longest lives of vertebrates on Earth, a new study reports. The results, published in the 12 August issue of Science, suggest the sharks can live for nearly three hundred years, and they reach sexual maturity at 150 years old.
The Greenland shark, Somniosus microcephalus, is widely distributed across the North Atlantic, with adults reaching lengths of 13 to 16 feet (400 to 500 centimeters). The biology of the Greenland shark is poorly understood, yet their extremely slow growth rates, at about one centimeter per year, hint that these animals live exceptionally long lives.
The traditional methods for determining the age of a species involve analyzing calcified tissue such as bone, a feature that's sparse in Greenland sharks. To determine the average age of this species, Julius Nielsen at the University of Copenhagen and colleagues applied radiocarbon dating techniques to the eye lenses of 28 females accidentally entrapped in fishing nets. Their analysis suggests an average lifespan of at least 272 years for the sharks. The two largest sharks in the study, at 493 centimeters and 502 centimeters in length, were estimated to be roughly 335 years old and 392 years old, respectively.
What's more, since previous reports suggest that females of this species reach sexual maturity at lengths greater than 400 centimeters, they could become mature at 156 years old, the scientists say.
Nielsen cautions that there is a lot of uncertainty in these estimates. "What we can say is that with 95% certainty the oldest shark was between 272 and 512 years old," he said. "Even the lower part of this uncertainty, which is that the sharks can live for at least 272 years, makes the Greenland shark the longest living vertebrate animal in the world."
The previous record holder for the longest-living vertebrate was an Aldabra giant tortoise named Adwaita, estimated to have lived until the ripe age of 255. In the oceans, the bowhead whale is estimated to live about 211 years. Among invertebrates, the ocean quahog Arctica islandica, a North Atlantic clam, may live as long as 507 years.
Nielsen recalls the first time he saw a Greenland shark, in 2010. "I remember that I was super fascinated about this animal — it was enormous and it was just lying there. Big, docile, and mysterious."
Nielsen has numerous questions left to explore about these mysterious creatures. "I want to know more about their population genetics, how they hunt in the deep ocean, if they really are blind as has been suggested, what their migration [patterns] are [like], and much more," he said.
[Credit for related image: Julius Nielsen]