Featured Image Credit: FRANCO BANFI, NATURE PICTURE LIBRARY/ALAMY
By: Jessica Kittel
Slow and steady wins the race. Just ask the Greenland shark, recently awarded the title of the longest living marine vertebrate. These behemoths are estimated to live to be upwards of 400 years old, according to recently published research.
The Greenland shark (Somniosus microcephalus) aka sleeper shark or gurry shark is the second largest carnivorous shark (the great white gets first place). While they can grow to be up to 20 feet long, it takes them a very long time to get there. They only grow roughly one centimeter per year. Due to this piece of information, it has long been theorized that this species of shark have very long lifespans but, until recently, effectively calculating their age remained a mystery. Not anymore!
Researchers John Steffensen and Julius Nielsen from the University of Copenhagen had to get creative to determine the age of this slow-moving, cold-water residing shark. Using the lenses of the sharks’ eyes, they used radiocarbon dating to look for high levels of carbon-14. Carbon-14 was released into the environment in large quantities in the mid-1950s during nuclear bomb testing. By the 1960s the extra carbon released had made its way into every ocean ecosystem so the researchers were able to test for the presence of carbon-14 to determine if the sharks they were testing were born before or after the 1960s.
After specifically dating two of their specimens Steffensen and Nielsen were able to create a general growth curve that could be used to determine the age of any Greenland shark based on their size. Using the knowledge that these sharks are 1.4 feet in length when born, they were able to determine that the oldest specimen was 392 years old (give or take 120 years). Even if they were to go with the most conservative estimate of 272 years, these sharks still outrank the previous record holder (the bowhead whale) by more than 50 years!
They also determined that Greenland sharks don’t actually hit sexual maturity until they’re 150 years old, a piece of information that could have huge impacts on conservation strategies for this species.