Talk About An Ancient Mariner! Greenland Shark Is At Least 272 Years Old

Aug 11, 2016
Originally published on August 15, 2016 10:41 am

Sharks can live to be at least 272 years old in the Arctic seas, and scientists say one recently caught shark may have lived as long as 512 years.

That's according to a study published Thursday in the journal Science that says Greenland sharks can live longer than any other known animal advanced enough to have a backbone. Until now, the record-holder for the oldest vertebrate was the bowhead whale, known to have lived up to 211 years.

The Greenland shark, a massive carnivore that can be more than 16 feet long, hasn't been studied much, and its life in the cold northern waters remains largely mysterious. Julius Nielsen, at the University of Copenhagen in Denmark, says there had been some hints that Greenland sharks grow very slowly, perhaps less than a centimeter per year. That suggested the huge sharks might be ancient.

"We only expected that the sharks might be very old," says Nielsen. "But we did not know in advance. And it was, of course, a very big surprise to learn that it was actually the oldest vertebrate animal."

He and some colleagues obtained 28 female Greenland sharks taken by research vessels as unintended bycatch from 2010 to 2013. The researchers then used radiocarbon dating techniques on the lenses of the sharks' eyes.

There's a bit of uncertainty associated with the age estimates, but Nielsen says the most likely age for the oldest shark they found was about 390 years. "It was, with 95 percent certainty, between 272 and 512 years old," he says. The researchers believe these sharks reach sexual maturity at about the age of 150 years.

"It's a fascinating paper and certainly moves back the vertebrate longevity record by a substantial amount," says Steven Austad, who studies the biology of aging at the University of Alabama, Birmingham. "Even if you look at the low end of their estimate — 272 years — that's still substantially longer than any other documented vertebrate."

He says there are lots of anecdotal accounts of long-lived turtles and fish, but this beats those by a long shot.

The Greenland shark's lifespan may really only be surpassed by that of the ocean quahog. These clams have annual growth rings on their shell, and scientists have found that they can live as long as 507 years.

The Greenland shark, the bowhead whale and the oldest ocean quahogs spend their long lives in cold northern waters, notes Austad, suggesting that low temperatures might have something to do with their unusual longevity.

"I don't think that cold is the whole story," says Austad. "It's probably playing a role. But my guess is there are plenty of short-lived animals that are swimming around with this shark."

Still, he says, just imagine what it would be like to have muscles, like these sharks, that have been working nonstop since the time of the Pilgrims.

"There's something going on in those muscles that we'd very much like to know about," says Austad.

He notes that Greenland sharks would not be easy to study in the lab, but perhaps people could study shark cells grown in a dish.

"Probably whatever sort of physiological tricks the sharks have to live that long, and the quahogs have to live that long, they're probably something that humans don't have," says Austad. "But it's something that, if we discover what it is, we might be able to adapt it to human use."

He's been studying the quahog, which has a beating heart, and whenever doctors who specialize in geriatrics stop by, he likes to hand them a 200-and-something-year-old clam and tell them they're holding a beating heart that's older than any heart they'll encounter in their entire career.

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Imagine what it would be like to live for centuries. That's the reality for a kind of shark. The Greenland shark swims in the dark, frigid waters of the Arctic seas. And as NPR's Nell Greenfieldboyce reports, scientists say it could live for about 400 years or even longer.

NELL GREENFIELDBOYCE, BYLINE: The first time Julius Nielsen ever saw a Greenland shark, he was working on a research vessel that was studying other Arctic fish.

JULIUS NIELSEN: One day we - by accident - caught a Greenland shark. It was a really a big one, and everyone went up and saw this interesting animal.

GREENFIELDBOYCE: It looked different than a great white shark, but it had the shark fins and big teeth. Nielsen was intrigued.

NIELSEN: You don't really expect sharks to be swimming around between icebergs and things like that.

GREENFIELDBOYCE: He soon learned that scientists know almost nothing about the Greenland shark.

NIELSEN: Perhaps, the biggest of the mysteries was how old these apparently very slow-growing sharks get.

GREENFIELDBOYCE: Biologists had some hints that these sharks grow less than a centimeter a year, but adult sharks can be over 16 feet long. So if they were really slow-growing, they'd have to live a long time. To test that idea, Nielsen teamed up with some colleagues at the University of Copenhagen in Denmark where he works as well as researchers in other countries. They obtained 28 female Greenland sharks that were caught accidentally, and then they used radiocarbon dating techniques on the lenses of the sharks' eyes. The results were astonishing. These sharks live longer than any other creature advanced enough to have a backbone.

NIELSEN: We only expected that the sharks might be very old. And it was, of course, a very big surprise to learn that it was actually the oldest vertebrate animal in the world.

GREENFIELDBOYCE: The most likely age of the biggest, oldest shark was about 390 years. But there is some uncertainty in that estimate.

NIELSEN: What we can say is that it was with 95 percent certainty between 272 and 512 years old.

GREENFIELDBOYCE: The results appear in the journal Science, and they impressed Steven Austad. He studies the biology of aging at the University of Alabama at Birmingham.

STEVEN AUSTAD: It's a fascinating paper, and it certainly moves back to the vertebrate longevity record by a substantial amount.

GREENFIELDBOYCE: Until now, that record was held by the bowhead whale Austad says its maximum lifespan has been shown to be at least 211 years. And while you hear other tales of long lived turtles or fish, they're hard to verify.

AUSTAD: The reports are virtually all anecdotal.

GREENFIELDBOYCE: He says the Greenland shark age estimates are convincing. And if these sharks really can live as long as five centuries...

AUSTAD: That means the pilgrims, you know, may have been around the same time some shark that's swimming around now was born.

GREENFIELDBOYCE: Austad studies a kind of clam that can live for more than 500 years. Scientists know that because its shell has annual growth lines that can be counted like the rings inside a tree. He notes that the oldest specimens of this clam have come from waters near Iceland, and the bowhead whale and Greenland shark also both live far up north.

AUSTAD: So there does seem to be something that's attributable to cold or living in the cold that may confer longevity.

GREENFIELDBOYCE: He says it would be great to figure out what that icy secret is. Nell Greenfieldboyce, NPR News. Transcript provided by NPR, Copyright NPR.