400-year-old Greenland shark might be oldest vertebrate on Earth

Greenland sharks, living in the cold, deep waters of the Arctic and North Atlantic Oceans, are one of the largest sharks in the world — they can grow up to seven meters in length.

Now, scientists have discovered that Greenland sharks can live for hundreds of years, making them the world’s longest living vertebrates.

By carbon dating the eyes of 28 dead female Greenland sharks (Somniosus microcephalus), researchers estimate that the oldest shark was 392 years old when it was caught four years ago. The findings were published last week in Science.

“Our lifespan study is based on the carbon-14 dating of Greenland shark eye lenses,” lead author Julius Nielsen, a PhD student at the University of Copenhagen’s Department of Biology, explained in a statement. “As with other vertebrates, the lenses consist of a unique type of metabolically inactive tissue. Because the center 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.”

This carbon-14 dating technique is relatively new, researchers say, and has previously been used to estimate the age of whales, but not fish. The method also has a wide margin of error of 120 years. So the study estimates that the sharks likely live between 272 to 512 years.

The previously known longest living vertebrate — the bowhead whale — can live for around 211 years, which is less than the lower estimate of a Greenland shark’s lifespan. This makes the nearly 400-year-old shark the oldest known backboned animal, researchers say.

The Greenland sharks, currently listed as Near Threatened on the IUCN Red List, were once killed in large numbers for their liver oil. Now, these animals often get trapped as bycatch in fish traps, gillnets and shrimp trawl fisheries, according to the IUCN.  But their previous population declines and the current status of their populations, remain largely unknown.

“Greenland sharks are among the largest carnivorous sharks on the planet, and their role as an apex predator in the Arctic ecosystem is totally overlooked,” Nielsen said. “By the thousands, they accidentally end up as by-catch across the North Atlantic and I hope that our studies can help to bring a greater focus on the Greenland shark in the future.”

CITATION:

• Nielsen J, et al (2016) Eye lens radiocarbon reveals centuries of longevity in the Greenland shark (Somniosus microcephalus). 353(6300), pp. 702-704, DOI: 10.1126/science.aaf1703

Article published by Shreya Dasgupta

Animals, Conservation, Environment, Fish, Marine Biodiversity, Marine Conservation, Oceans, Sharks, Sharks And Rays, Wildlife

Arctic, Arctic Ocean, Atlantic Ocean

Print