The Greenland shark can live for centuries, longer than any other known vertebrate.
Greenland sharks glide through the cold, dark North Atlantic more slowly than almost any fish their size. They may not breed until they are around 150 years old. By dating crystals in the lenses of their eyes, scientists estimate a lifespan of at least 272 years, the longest of any known vertebrate.
The Greenland shark is one of the largest sharks alive, usually 4 to 5 metres long, and lives in water just above freezing, often hundreds of metres down, across the North Atlantic and Arctic. It is famously sluggish, averaging about a third of a metre per second, the lowest swimming speed for its size of any fish. That makes it a puzzle that seals turn up in its stomach; biologists suspect it ambushes them while they sleep. It also scavenges, and remains of moose, horses and even an entire reindeer have been found inside.
Working out a shark's age is difficult, so researchers turned to radiocarbon dating of crystals within the lenses of their eyes. The results suggested a lifespan of at least 272 years, with the oldest individual in the study estimated at 392 years, give or take 120. Females are thought to reach maturity at around 150 years, and a pregnancy may last somewhere between 8 and 18 years. One shark tagged in 1936 and caught again in 1952 had grown only about a centimetre a year.
Such a slow life seems tied to the cold and a very slow metabolism, and the species is now being studied for clues to longevity. Its genome, published in 2024, is huge, and more than two-thirds of it is made up of 'jumping genes' that can copy themselves around. Researchers suspect an unusual set of DNA-repair genes helps limit the damage. Many Greenland sharks are nearly blind, thanks to a parasitic crustacean that attaches to their eyes, yet they seem to cope well using smell and their pressure-sensing lateral line.
Their flesh is toxic unless treated, because of high levels of a compound called TMAO; in Iceland it is fermented and dried for months to make the pungent delicacy hákarl. Today the biggest threat is accidental capture, with an estimated 3,500 caught each year as bycatch. For an animal that takes a century and a half to breed, even modest losses could take centuries to make good.
Source: Wikipedia — Greenland shark · Text summarised from Wikipedia (CC BY-SA 4.0)
