In the midst of Shark Week, it only seems fitting to do a post about sharks. The shark I’ve chosen to write about isn’t one of the most popular or well known species, and it’s generally not one that shows up in many television shows; however, it’s worth taking the time to learn about!
Somniosus microcephalus, also known as the Greenland shark or Sleeper shark, is one of the larger species of shark and can reach up to 24 feet in length. It is a member of the class elasmobranch, which is a group that includes sharks, rays and skates, and therefore it has a skeleton made of cartilage rather than bone. Sightings of this species of shark are quite rare. The first underwater photos of a Greenland shark weren’t taken until 1995, and the first video of one swimming in its natural habitat wasn’t taken until 2003. Because of this, not much is known about the Greenland shark, although research is now being conducted by a Canadian group known as the Greenland Shark and Elasmobranch Education and Research Group, or GEERG.
The Greenland shark is a pretty strange looking guy:
He is also reaalllly slow, averaging a cruising speed of 0.76 mph. This sluggish speed works well for these sharks due to their preferred habitat in the Northern Atlantic and Arctic regions, in cold waters ranging from -0.6 to 12°C. A slowed metabolism allows them to be the only species of shark that can tolerate cold temperatures year round. They also age slowly, with a growth rate estimated between 0.5 to 1.1 cm a year (which puts the 7 meter, or 24 foot long, individuals at an estimated age of over 200 years!)
One very interesting fact is that the Greenland shark often plays host to a parasitic copepod (small crustacean) called Ommatokoita elongata. This parasite attaches to the eyes of the shark, feeding off of the tissue and rendering him blind. Fortunately, the shark seems unaffected by it since it relies much more on its sense of smell than on vision to search for food. The Greenland shark’s food of choice is fish, such as salmon and cod, and any carrion it can sink its teeth into. Marine mammals such as seals have been found in the contents of this shark’s stomach, however it is uncertain as to whether they are able to catch a live seal. Other remains of animals found in the Greenland shark’s stomach include polar bears, porpoises, moose, horses, and in one case an entire reindeer.
The Greenland shark is ovoviviparous, meaning that the female carries eggs within her body until the embryos are full term. They then hatch within her body and are born live, with no placental attachment.
The flesh of the Greenland shark is toxic to humans due to the presence of TMAO (trimethylamine oxide) that is used by the shark to regulate osmotic pressure as well as working as a natural antifreeze. It is still eaten in Iceland as a delicacy: the meat is first compressed in large containers to remove the toxins and then allowed to dry outside for 2-4 months, after which it is safe to consume.
I will end this post with this brief video of a Greenland shark encounter. Thanks for stopping by!