Meet the longest-living vertebrate in the world, the Greenland shark.
Found primarily in the frigid waters of the North Atlantic, these slow-swimming sharks can be as big as the largest great whites, reaching up to 21 feet in length. They're among the largest of carnivorous fish, and yet grow perhaps only a centimeter or so a year. Such slow growth yet big size is usually an indicator of a long-lived animal. But researchers weren't expecting what they discovered when they radiocarbon dated lenses from the eyes of 28 Greenland sharks.
"We only expected that the sharks might be very old," Julius Nielsen, at the University of Copenhagen in Denmark, told NPR in 2016. "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."
According to Science Magazine:
[R]esearchers correlated radiocarbon dates with shark length to calculate the age of their sharks. The oldest was 392 plus or minus 120 years [...]. That makes Greenland sharks the longest lived vertebrates on record by a huge margin; the next oldest is the bowhead whale, at 211 years old. And given the size of most pregnant females — close to 4 meters — they are at least 150 years old before they have young, the group estimates.
Imagine being 150 years old before you're ready to have your first child! Imagine being born before the United States was even a reality. For humans — who rarely make it to a century mark — it's difficult to fathom.
Little is known about Greenland sharks, even basics such as where they give birth or how many of them there are, though researchers at a July 2017 symposium at the University of Exeter speculated that they may mate in "hidden" Arctic fjords. No one has even witnessed one hunting, though they have been found to have polar bear, seals, fast-swimming fish and even moose in their stomachs.
Given the sharks' incredibly long lifespans, scientists are diving into the sea creature's genome, looking for clues. That symposium also highlighted the work being done to isolate the shark's longevity gene, with complete DNA information gathered from almost 100 sharks, including some born in the 1750s. Finding such a gene could go a long way in explaining why some vertebrates, like humans, have such limited lifespans.
These sharks also serve as swimming history books. Their tissue, bones and DNA could tell us a great deal about the waters of the world from a time before the Industrial Revolution, large-scale commercial fishing and the pronounced ocean pollution we see today.
Check out what it's like to swim with one in this encounter with what is a small and young — and yet to us, still fairly old — Greenland shark.
This file was originally published in August 2016 and has been updated with additional information.
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