Greenland sharks could tell a few stories. Image via University of Copenhagen
With sexual maturity of 150 years, and growing just 1cm a year, Greenland sharks are the grandfathers of the seas, according to new research.
Pinning the age of a Greenland shark at 392, plus or minus 150 years, scientists have just labelled the relatively unknown predator as the oldest vertebrate animal in history.
New champion
Replacing the bowhead whale – 211 years in one example – atop the table, it leaves humans (122 years) and even elephants (86) trailing in its wake.
At more than five metres long, the Greenland shark has remained a bit of a mystery for centuries. Caught up in fishing nets on occasion, scientists have never been truly able to date these beasts, until now.
Using a pretty novel age-estimation process, which involved carbon-dating the eyes of accidentally-caught specimens, scientists at the University of Copenhagen have established the epic age of the shark for the first time.
Suggesting that sexual maturity is only reached after 150 years, the Julius Nielsen-led research has been published in Science.
Greenland sharks caught by fishermen. Image via University of Copenhagen.
The eye sees all
“As with other vertebrates, the [shark’s eye lenses] consist of a unique type of metabolically-inactive tissue,” said Nielsen.
“Because the centre of the lens does not change from the time of a shark’s birth, it allows the tissue’s chemical composition to reveal a shark’s age.”
By comparing the layers of carbon to specific global events, approximate ages were established. One such series of events was the atomic bomb tests of the 1950s, with increased carbon-14 released into the atmosphere with each explosion.
The pulse of this hit the North Atlantic in the 1960s so, finding spikes in carbon-14 in the eye lenses could be pinned to this era.
That provides a useful timestamp, said Nielsen. “We use well-established radiocarbon methods, but combine them in a new way. This approach, along with the extraordinary ages for these sharks makes this study highly unusual,” according to Julius Nielsen.
A Greenland shark swimming about, being old. Image via NOAA Okeanos Explorer Program/Wikimedia Commons
The summer of love
Testing 28 sharks, the team found that three had high levels of carbon-14, meaning they were born in the 1960s, with one born in the very early part of the decade.
The rest, according to the research, are older, with the largest of the sharks, measuring just over five metres in length, estimated to be 392 years of age, with that 150-year margin of error.
“The Greenland shark is now the best candidate for the longest-living vertebrate animal,” he said.
The longevity of these sharks is “astonishing”, according to Michael Oellermann, a cold-water physiologist in Denmark, who was not involved with the work.
Given the constant threat of predation, disease, scarcity of food and general luck, the Greenland sharks are extraordinary.
“Who would have expected that nuclear bombs [one day] could help to determine the lifespan of marine sharks?” said Oellerman in Science.
