Level 4
Byline: Associated Press
In the cold waters of the Arctic, a creature of the deep lurked for centuries. Now scientists calculate that this female Greenland shark was the Earth's oldest living animal with a backbone.
They estimated that the gray shark, part of the species named after Greenland, was born in the icy waters roughly 400 years ago and died only recently. That conclusion puts the entire species at the top of the longest-living-animal list.
Using an unusual dating technique, an international team of biologists and physicists estimated the age of 28 dead female Greenland sharks based on tissue in their eyes. Eight of the sharks were probably 200 years or older and two probably date back more than three centuries, according to a study published last week in the journal Science.
Until now, that record holder was a bowhead whale that hit 211 years old, according to study lead author Julius Nielsen.
The oldest of the Greenland sharks examined was nearly 16 1/2 feet long and estimated to be 392 years old when it was caught about four years ago. But that calculation comes with a huge margin of error -- plus or minus 120 years -- due to the newness of the dating technique, said Nielsen, a marine biologist at the University of Copenhagen in Denmark.
That means the shark was probably born sometime between 1500 and 1740 with the most likely birth year 1620.
"It's an estimate. It's not a determination," Nielsen said. "It is the best we can do."
Scientists are confident the shark would have been at least 272 years old when it died, so it still would be the longest-living animal with a backbone, Nielsen said. Other experts agreed.
Joao Pedro Magalhaes, a University of Liverpool aging researcher, said he wouldn't necessarily concentrate on exact numbers, especially when they are more than 400 years.
"But the study is convincing enough for us to say that these animals live way longer than human beings and possibly longer than any other vertebrate," said Magalhaes, who runs AnAge, an animal longevity database. He wasn't part of Nielsen's team.
Some animals without backbones live longer. A clam lived 507 years, and two types of sponges are said to survive for 15,000 and 1,500 years.
While not surprised that Greenland sharks live a long time, "I'm really shocked by the magnitude of that longevity," wrote Christopher Lowe, director of the shark lab at California State University at Long Beach. He wasn't part of the study, but said it was creative and compelling.
Greenland sharks love cold water -- preferring temperatures near freezing -- and are all over the Arctic. The cold water and the slow metabolism that comes with it might have something to do with their long lives, Nielsen said. Lowe, in an email, said "the rule of thumb is deep and cold = old when it comes to fishes."
"I don't know why they get as old, but I hope someone will find out," Nielsen said.