Description & Behavior
Greenland sharks, Somniosus microcephalus (Bloch and Schneider, 1801), aka sleeper sharks, are named for their lethargic behavior; Somniosus, which refers to “sleep”, and microcephalus which means “small head.” In spite of their small heads, Greenland sharks are large, robust sharks that reach up to 6.5 m in length and weigh up to 900 kg. They have short, rounded snouts, small eyes, and small but sharp teeth. Their dorsal and pectoral fins are also quite small, as are their gill slits in relation to their body size. They are brown, gray, or black in color, and some may have dark lines or white spots on their dorsal (upper) sides or along their flanks.
World Range & Habitat
Greenland sharks, Somniosus microcephalus, are found between 80°N-55°S in the northern Atlantic and Arctic regions, although sightings have been reported south near France and Portugal, as far west as the Gulf of St. Lawrence, and as far south as off Cape Cod and North Carolina. Sightings have also been reported in the Southern Atlantic near Argentina and even in Antarctic waters. Greenland sharks are a deep-water species that inhabits cold waters between 1-12°C, near the continental and insular (island) shelves and upper slopes down to at least 1,200 m. In the Arctic and subarctic Atlantic, however, Greenland sharks can be found during the colder months inshore in intertidal areas and even at the surface of shallow bays and river mouths.
Feeding Behavior (Ecology)
Greenland sharks, Somniosus microcephalus, feed on pelagic (open water) and bottom fishes, other sharks, skates, eels, seals, small cetaceans, sea birds, squids, crabs, amphipods, marine snails, brittle stars, sea urchins, and jellyfish (i.e., just about anything). Greenland sharks are also known to feed on carrion, including reindeer and even a dead horse.
Greenland sharks, Somniosus microcephalus, are an ovoviviparous species. Pups measure about 38 cm at birth and litter size is between 5-10 young.
Ovoviviparous: eggs are retained within the body of the female in a brood chamber where the embryo develops, receiving nourishment from a yolk sac. This is the method of reproduction for the “live-bearing” fishes where pups hatch from egg capsules inside the mother’s uterus and are born soon afterward. Also known as aplacental viviparous.
Conservation Status & Comments
Greenland sharks are hunted commercially and recreationally. Their meat is dried and sold for human and dog consumption. In its fresh form, their flesh is said to be toxic when eaten because the flesh contains high concentrations of urea and trimethylamine oxide, which induces a intoxicating affect (see Eating Rotten Shark Meat for more information).
References & Further Research
Greenland Shark Eats A Polar Bear — Sleeper Shark Facts, Lifespan, Diet, And Video
Greenland Shark, Somniosus microcephalus (Bloch and Schneider, 1801) ~ GEERG
Arctic Kingdom Marine Expeditions – Greenland Shark (image galleries)
Research Somniosus microcephalus @
Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS