Greenland Shark Lives at Least 272 Years

This Greenland shark has just been tagged and is swimming toward Uummannaq Fjord in northwestern Greenland.

There is a shakeup in the list of the world's longest-lived animals, as researchers have just determined that Greenland sharks live to be at least 272 years old, making them the vertebrates -- animals with a backbone or spinal column -- with the longest-known life expectancy.

Like an Olympic race for longevity, the Greenland sharks now exceed other incredibly long-lived animals, such as bowhead whales and tortoises. The findings, reported in the journal Science, indicate that the large, carnivorous sharks could even live much longer than 272 years.

Julius Nielsen, a doctoral student at the University of Copenhagen and the Greenland Institute of Natural Resources, told Discovery News: "We report the oldest shark to be at least 272 years (old). In more technical terms, it is with 95% certainty between 272 and 512 years old."

He added that the shark most likely died at around 390 years old, but due to the noted age range, he and his team stuck with the lower and more conservative figure for the paper.

It has long been suspected that Greenland sharks live ultra-long lives, but figuring out just how long has stumped marine biologists for decades. Usually the age of sharks and rays can be determined by counting seasonally deposited growth layers in hard calcified structures, such as fin spines. Greenland sharks, however, lack these hard structures.

To get around the problem, Nielsen and his team analyzed the eye lens nucleus of 28 female sharks sampled as accidental by-catch during the Greenland Institute of Natural Resources' annual fish and shrimp surveys. The research project is nicknamed Old and Cold, referring to the sharks' chilly environment and advanced ages.

Co-author Christopher Bronk Ramsey, a professor of archaeological science at the University of Oxford, told Discovery News, "The eye lens in all large animals forms during the initial development of the animal, and so dating this gives the age of the animal. Other body parts typically grow, or at least the carbon overturns over time. This is not possible for the lens because it has no internal blood supply."

The scientists measured the radiocarbon content of the Greenland shark eye lenses. Then, they estimated the age of the individuals by matching and calibrating the data using data representing radiocarbon changes in the northern North Atlantic marine food web the past 500 years.

The study marks the first time that scientists have applied a radiocarbon approach on eye lenses to date the longevity of a fish, which sharks are. Ramsey indicated that even he is in awe of the fact that the Bayesian statistics behind some of his and his colleagues' work were formulated in the 18th century, when the oldest of the sharks in the study were alive.

"This perhaps puts quite nicely into perspective how long the lives of these animals are, and conversely, how much humans have achieved within the lifetime of one of these sharks," he said.

A Greenland shark in the icy waters of Disko Bay, western Greenland.

The researchers estimate that the long-lived Greenland sharks do not reach sexual maturity until around 156 years of age. Ramsey suspects that, since females have to attain a certain size to keep the developing shark embryos within their bodies, they cannot begin to mate until they reach that size. Their growth rate is incredibly slow.

As for why this rate is so slow, and why the sharks live such long lives, Ramsey said these characteristics are probably due to "low metabolic rate, cold temperatures and limits to food supply. The shark is a very slow moving, cold-blooded species."

Researchers like Michael Keane of the University of Liverpool are studying long-lived animals to determine if they possess special genes or other features that help to safeguard them against age-related diseases, particularly cancer. Such research is still in its relative infancy, so more revelations about nature's own 'fountain of youth' are yet to come.

Ramsey said at least one commonality seems to apply to all of the long-living species: a very low metabolic rate.

Read more at Discovery News