There are plenty of animals on Earth that are pretty good at sticking around. Elephants can live into their 80s, the world's oldest tortoise survived until around 250, and bowhead whales can reach the ripe old age of 200. But a new study has revealed the enigmatic Greenland shark to be the longest-living vertebrate on Earth, with one specimen estimated to be a whopping 392 years of age.
The Greenland shark is found in the waters of the North Atlantic and can reach lengths of 4 to 5 m (13 to 16 ft). They take their sweet time in getting there, however, with growth rates of about 1 cm (0.4 in) per year.
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Not a whole lot is known about the biology of the Greenland shark, but this slow growth rate has led biologists to suspect it has an exceptionally long lifespan. One was captured and tagged near Greenland in 1936 and then recaptured 16 years later, with researchers recording an increase in length of just 6 cm (2.4 in). This led them to estimate that the shark was more than 200 years old.
But a new study has indicated that Greenland sharks are capable of living much, much longer than that. Researchers from the University of Copenhagen used radiocarbon dating techniques on the eye lenses of 28 female sharks that were inadvertently captured in fishing nets.
Through their analysis, the team estimates that the oldest shark of the group, which measured a mammoth 502 cm (16.5 ft) in length, is 392 years old. One slightly shorter shark, of 493 cm (16.2 ft) in length, was calculated to be 335 years old, with the average lifespan of the entire group estimated to be 272 years.
Based on earlier research suggesting female Greenland sharks reach sexual maturity at lengths of 400 cm (13.1 ft), the scientists say they may not even start to reproduce until the age of 156. They note that there is still much uncertainty around the estimates, but they paint a clear enough picture to conclude the Greenland shark is unmatched when it comes to longevity.
"What we can say is that with 95 percent certainty the oldest shark was between 272 and 512 years old," says Julius Nielsen from the University of Copenhagen. "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."
Nielsen is now working to learn more about the mysterious creatures and answer questions about their genetics, how they hunt, what their migration patterns are like and if they are indeed blind as has been suggested.