The Greenland shark’s scientific name is Somniosus microcephalus, and its Latin name roughly translates into “sleepy little head.” This species has been described in scientific literature as “notably sluggish.”
Lumpish, with stunted pectoral fins that they use for ponderously slow swimming in cold and dark Arctic waters, they have blunt snouts and gaping mouths that give them an unfortunate, dull-witted appearance.
They grow between 8 and 14 feet but can reach up to 23 feet and weigh up to 1.5 tons. Greenland sharks are among the largest sharks in the world, comparable in size to great whites.
Greenland sharks are one of many fish that live in the waters around Greenland, though this is not the only area in which the shark inhabits. These sharks, which are sometimes referred to as “gray sharks” or “gurry sharks,” can also be found in the north Atlantic Ocean near Iceland, Norway, and Canada.
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. This toxicity is due to trimethylamine oxide (TMAO) in the tissue of Greenland shark flesh, which helps the fish stabilize their enzymes and structural proteins against the debilitating effects of severe cold and high water pressure.
Nonetheless, Greenland shark meat can be prepared in a fermentation process that removes the TMAO, resulting in a much-enjoyed national dish of Iceland. This dish, known as Hákarl or kæstur hákarl, is prepared by hanging the meat of the Greenland shark up for four to five months, thus removing the adverse effects of the neurotoxins. This species was not even captured on film for the first time until 1995, and it took 18 more years for anyone to get a video that depicted Greenland sharks in their natural environment.
The Greenland shark is an apex predator and mostly eats fish, and it has been observed actively hunting seals in Canada. The prey found in the stomachs of Greenland sharks is an indicator of the active hunting patterns of these predators.
Recorded fish prey has included smaller sharks, skates, eels, herring, capelin, Arctic char, cod, rosefish, sculpins, lumpfish, wolffish, and flounder. Small Greenland sharks eat predominantly squid, while the larger sharks over 79 inches were discovered eating prey such as epibenthic and benthic fishes as well as seals. The largest of these sharks were found having eaten redfish and other higher trophic level prey.
Using their cryptic coloration, they can approach prey undetected before closing the remaining distance by opening their large buccal cavity in order to create a suction that draws in the prey. This is the likely explanation as to why the gut contents discovered in Greenland sharks are often whole prey specimens.
One of the primary reasons Greenland sharks are spotted so infrequently is their ability to dive to such extreme depths. Researchers have recorded them going as deep as 7,218 feet, and they can sometimes be found relaxing on the slopes and shelves far under the ocean’s surface.
All sharks are cold-blooded, but this particular species truly thrives in a frigid environment. Greenland sharks prefer to stay in water ranging from 30.2 to 50°F, and they migrate to the coldest part of the water each season. Indeed, Greenland sharks are the only known shark species that can tolerate Arctic conditions all year long.
Many shark species can be aged by counting growth bands on their vertebrae, like rings on a tree. The Greenland shark’s soft vertebrae do not have these bands, however. Instead, its age is determined by removing the layers of the lens of its eye—which continues growing throughout its lifetime—and radiocarbon dating the tissue in the center.
The mystery might have lingered were it not for the work of three Danish scientists—a physicist named Jan Heinemeier and two marine biologists, John Fleng Steffensen, and Julius Nielsen. Nine years ago, Heinemeier and four of his colleagues published a paper on lens crystallines, a class of proteins found in the human eye. Like all organic molecules, crystallines contain carbon, including trace amounts of the radioactive isotope carbon-14. Unlike other proteins, which undergo constant recycling and replenishment, crystallines remain stable throughout a person’s life;
they are envelopes sealed at birth, their contents an artifact from the womb. And, if crystallines are the envelopes, then carbon-14 is the postmark. The isotope has always occurred naturally on Earth, formed wherever incoming cosmic rays strike the atmosphere, but some of the current supply also comes from nuclear weapons tests. The level fluctuates from year to year, and that means that every given time period has its own carbon-14 signature.
(There was a particularly huge spike, called the bomb pulse, in the nuke-happy heyday of the fifties and sixties.) Experimenting on cadavers’ lenses, Heinemeier found that he could measure how much carbon-14 they contained and use it to determine the deceased’s date of birth.
Using this method it has been determined that Greenland sharks can live up to and beyond 500 years. It is firmly established Greenland sharks are the longest-living vertebrates on Earth. In theory, the biggest ones could be nearly six centuries old.
- Carbon-14, C-14, 14 C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological, and hydrogeological samples. Carbon-14 was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934. [Back]