The Greenland shark is an old, misunderstood late-bloomer.
You might be inclined to feel sorry for it—but this vertebrate lives a long, slow-going life. A team of researchers led by Julius Nielsen of the University of Copenhagen has determined that it can live to at least 272 (possibly up to 500) years old.
This shark grows slowly: the cold environment retards its metabolism, safeguarding tissue from damage. And its actual body size increases by only a centimeter per year. Female Greenland sharks are in no rush to reproduce; they likely reach mid-life at 156 years old, when they’re finally ready to start breeding.
Sharks are made of mostly cartilage, which makes it difficult for scientists to pinpoint their exact age. So Nielsen and his team focused in on the Greenland shark’s eyes instead.
Here’s Mary Bates, reporting for National Geographic News:
Greenland sharks have a unique eye structure in that the lens grows throughout an animal’s lifetime. The older an animal gets, the more layers are added to the lens. Scientists can’t count the layers as they would tree rings, but they can remove all the layers that have been added over the years until they reach the center, or the embryonic nucleus, of the lens.
This tissue is composed of proteins that were formed when the shark was a young pup. Scientists can analyze the chemical composition of the eye lens nucleus to estimate an animal’s age.
Radiocarbon dating of the 28 Greenland sharks’ lens nuclei revealed a maximum life span of at least 272 years, according to the study, published August 11 in the journal Science .
The researchers determined that the oldest shark in the study appeared to be 392 years old.
That’s remarkable, but the scientists caution that we don’t yet know how many Greenland sharks are left in the world. If these animals don’t reach sexual maturity until they’re more than 150 years old, the species could be in grave danger, as climate change threatens to throw off their habitats and as fishers threaten to accidentally kill them off.
Photo credit: NOAA / Wikimedia Commons (Public Domain)