The Greenland shark is the longest-living vertebrate. The transparent tissue in the Greenland shark eye lens is metabolically inactive, with new layers added throughout the shark’s lifetime, much like the rings of a tree. Age estimations range between 252 and 512 years. Even if Greenland sharks typically lived only to the lower range of that estimate, they would be the longest-living vertebrate known to science.

The species is primarily found in the cold-water environments from the Arctic Ocean to the eastern USA. They are the only known shark species that can tolerate Arctic conditions all year long. If consumed, Greenland shark meat can cause symptoms in humans similar to severe inebriation, and the neurotoxins in their flesh can even be incapacitating to sled dogs. Greenland sharks are among the largest sharks in the world, comparable in size to great whites. They have been known to grow to 6.4 meters (21 feet).

Although Greenland sharks are large and strong, they are known to be especially non-confrontational. This species was not even captured on film for the first time until 1995, and it took another 18 years for anyone to get a video that depicted them in their natural environment. Researchers have recorded them diving as deep as 2,200 meters (7,218 feet), and they can sometimes be found relaxing on the slopes and shelves far under the ocean’s surface. Their average pace so slow and quiet, they are often called 'sleeper sharks' or 'zombies of the deep'.

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