Greenland sharks are now the longest-living vertebrates known on Earth, according to scientists.
Researchers used radiocarbon dating of eye proteins to determine the ages of 28 Greenland sharks, and estimated that one female was about 400 years old. The former vertebrate record-holder was a bowhead whale estimated to be 211 years old.
As lead author Julius Nielsen, a marine biologist from the University of Copenhagen, put it: “We had our expectations that we were dealing with an unusual animal, but I think everyone doing this research was very surprised to learn the sharks were as old as they were.”
Greenland sharks are huge and can grow up to 5m in length. Yet, they grow at just 1cm a year. They can be found, swimming slowly, throughout the cold, deep waters of the North Atlantic.
The team believes the animals only reach sexual maturity when they are 4m-long. And with this new, very lengthy age-range, it suggests this does not occur until the animals are about 150 years old.
The research was made possible, in part, by the atmospheric thermonuclear weapons tests conducted during the 1960s, which released massive amounts of radiocarbon that were then absorbed by organisms in ocean ecosystems. Sharks that showed evidence of elevated radiocarbon in the nucleus of their eye tissue were therefore born after the so-called “bomb pulse,” and were younger than 50 years old, while sharks with lower radiocarbon levels were born prior to that, and were at least 50 years old or older, the study authors wrote.
The scientists then calculated an age range for the older sharks based on their size, and on prior data about Greenland sharks’ size at birth and growth rates in fish.
According to the results of the analysis – which has a probability rate of about 95 percent – the sharks were at least 272 years old, and could be as much as 512 years old (!) with 390 years as the most likely average life span, according to Nielsen.
But why do Greenland sharks live so long? Their longevity is actually attributed to their very slow metabolism and the cold waters that they inhabit. They swim through the cold waters of the Arctic and the North Atlantic at such a sluggish pace that has earned them the nickname “sleeper sharks.” Seal parts have been found in their bellies, but the sharks move so slowly that experts have suggested that the seals must have been asleep or already dead when the sharks ate them.