If you think sharks are scary, wait until you hear about the Greenland shark. This mysterious creature is the longest-living vertebrate known, and it can also make you intoxicated with its toxic meat.
The Greenland shark, also known as the gurry shark or the eqalussuaq in Kalaallisut, is a large shark that inhabits the cold waters of the Arctic and North Atlantic oceans. It can grow up to 24 feet long and weigh up to 2,645 pounds, making it one of the largest living species of shark. It belongs to a family of sleeper sharks, which move slowly and stealthily through the water, sneaking up on live prey and scavenging a variety of dead animals, including other sharks, seals, drowned horses and polar bears.
But what makes the Greenland shark truly remarkable is its longevity. A 2016 study published in the journal Science estimated that Greenland sharks have a maximum life span of at least 272 years, based on analysis of the sharks’ eye tissue. Some scientists even suggest that they could live for more than 500 years, making them the oldest living animals on Earth.
How do they achieve such an impressive age? One possible explanation is their slow metabolism and growth rate, which are adaptations to living in the cold and dark depths of the ocean. Another factor could be their high concentration of trimethylamine oxide (TMAO) in their tissues, which helps them cope with the high pressure and low temperature of their environment.
However, this same compound also makes their meat toxic to humans. If the meat is eaten without being treated by drying or soaking, it will break down into a poisonous compound during digestion, causing effects similar to extreme drunkenness. “The untreated meat will literally make you ‘shark drunk’ because of the toxins,” according to Knowledge WOW, a website that answers curious questions.
Despite this risk, some people in Iceland and Greenland enjoy eating Greenland shark meat as a delicacy known as kæstur hákarl or hákarl. The meat is fermented for several weeks or months before being consumed, which reduces the toxin levels but also gives it a strong ammonia smell and taste.
Another peculiar feature of the Greenland shark is its eye parasite. Many of them are infected by a parasite called Ommatokoita elongata, which attaches itself to the eyes of the sharks and can grow up to an inch long. “The eye parasite tends to live in just one of the shark’s eyes so they usually don’t go completely blind,” according to Live Science, a website that covers science news and discoveries.
The parasite may impair the shark’s vision, but it does not seem to affect its hunting ability much, as the shark relies more on its other senses to catch prey in the dark ocean waters. The parasite may even have a mutualistic relationship with the shark, acting as a lure for potential prey or a deterrent for predators.
Speaking of predators, are Greenland sharks dangerous to humans? Not really. They are rarely encountered by humans, as they live in regions where people do not typically swim. The only known report of a possible attack by a Greenland shark on a person dates to 1859, according to Britannica, an online encyclopedia.
However, humans may pose a threat to Greenland sharks, as they are vulnerable to overfishing and climate change. They have slow growth, late maturity, and low reproductive rates, which make them susceptible to population decline. “Greenland sharks in Canada are required to be discarded alive, but the survival rate of these discarded sharks is also currently unknown,” according to Oceans North, an organization that promotes marine conservation in the Arctic.
The Greenland shark is a fascinating and mysterious animal that deserves more attention and protection. It is not only a living fossil that has witnessed centuries of history but also a potential source of scientific and medical insights. Who knows what secrets this ancient shark holds in its toxic flesh and parasitic eyes?
Relevant articles:
– Greenland sharks: Toxic, half-blind giants of the ocean, Live Science, January 7, 2023
– What We Don’t Know About Greenland Sharks Could Hurt Them, Oceans North, April 2023
– Greenland shark | Size, Age, & Facts | Britannica, Britannica, June 30, 2023