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The Greenland shark (Somniosus microcephalus) is a large, slow-moving shark of the family Somniosidae, native to the North Atlantic Ocean. It is renowned for its exceptionally long lifespan, making it the longest-living vertebrate known. This species is adapted to cold, deep waters and plays a significant role as an apex predator in its ecosystem.
Physical Characteristics
- Body shape
- torpedo
- Coloration
- Typically dark grey, brownish-grey, or blackish, often with lighter mottling or banding. The ventral side is usually lighter.
- Scale type
- placoid
- Mouth position
- subterminal
- Distinctive features
- Small eyes relative to body size, often parasitized by a copepod (Ommatokoita elongata) which can cause bioluminescence and impair vision., Blunt, rounded snout., Two small dorsal fins, without spines, located far back on the body., Lack of an anal fin., Asymmetrical caudal fin, with the upper lobe longer than the lower., Rough, placoid scales covering the skin.
- Dorsal fin
- Two small, spineless dorsal fins, positioned far posteriorly on the body, with the first dorsal fin originating behind the pelvic fin origin.
- Tail fin
- Asymmetrical caudal fin, with a longer upper lobe and a shorter, less developed lower lobe.
- Pectoral fin
- Relatively small and paddle-like.
- Distinctive fins
- Absence of an anal fin.
Identification Tips
Size and Shape
Very large, robust body with a blunt snout and relatively small eyes.
Fin Placement
Two small dorsal fins located far back on the body, behind the pelvic fins. No anal fin.
Coloration
Uniform dark grey to brownish-black, often mottled.
Eye Parasite
Often has a parasitic copepod (Ommatokoita elongata) attached to its cornea, which appears as a yellowish-white worm-like structure on the eye. This is a strong indicator for this species.
Slow Movement
Known for its extremely slow swimming speed, a characteristic of 'sleeper sharks'.
Habitat
- Water type
- saltwater
- Depth
- Typically found at depths ranging from 0 to 2,800 meters (0 to 9,186 feet), with a preference for deeper waters (below 200 meters) but occasionally observed near the surface, especially in winter.
- Environment
- Cold, deep oceanic waters, primarily associated with continental shelves and slopes, as well as abyssal plains. They inhabit both pelagic and benthic zones.
- Geographic range
- North Atlantic Ocean, from the eastern Canadian Arctic to the Barents Sea, including waters around Greenland, Iceland, Norway, and occasionally as far south as the Gulf of Maine and the Bay of Biscay.
Aquarium Information
- Care level: expert
- Temperament: aggressive
- Diet: carnivore
- Minimum tank size: Not suitable for aquaria due to extreme size, specialized habitat requirements, and deep-sea nature.
- Temperature: 1-12°C (34-54°F)
- pH level: 7.8-8.2
- Hardness: High (marine salinity)
- Compatibility: Not applicable for home aquaria. In the wild, they are apex predators.
- Special requirements: Requires vast, deep, cold, and dark environments with specific pressure conditions, making it impossible to keep in captivity outside of highly specialized research facilities, and even then, it's extremely challenging.
Wild Information
- Conservation status: near threatened
- Seasonality: No distinct seasonal migration patterns are well-documented; they are present year-round in their deep-water habitats, though some individuals may move into shallower waters during winter months in certain areas.
- Market price: Historically low, primarily for liver oil and meat (after processing to remove toxins). Currently, very low due to conservation concerns and toxicity.
- Commercial importance: low
- Taste: The fresh meat is toxic due to high concentrations of urea and trimethylamine oxide, which act as an antifreeze. If properly processed (fermented and dried), it becomes edible, known as 'hákarl' in Iceland, with a strong, ammonia-rich taste.
- Texture: Firm, dense, and somewhat rubbery when fresh; becomes very chewy and pungent after fermentation.
- Cooking methods: Fermentation, Drying
- Nutritional value: High in protein and fats, but the fresh meat is poisonous. Processed hákarl is a traditional food source, but its nutritional value is secondary to its cultural significance and unique preparation.
Key Facts
Longest-Living Vertebraterecord
The Greenland shark holds the record for the longest-living vertebrate, with an estimated maximum lifespan of at least 272 years, and potentially over 500 years, based on radiocarbon dating of eye lenses.
Slow Growth, Late Maturitybehavior
They grow extremely slowly, about 1 cm per year, and reach sexual maturity at an estimated age of 150 years, making them one of the slowest-maturing animals.
Deep-Sea Predatorbehavior
Despite their slow speed, they are effective apex predators, preying on fish, seals, and even reindeer and polar bears (likely scavenged).
Toxic Meatinteresting
Their flesh contains high concentrations of urea and trimethylamine oxide, which act as an antifreeze but make the fresh meat toxic to humans and dogs. It must be fermented and dried to be edible (hákarl).
Parasitic Copepodinteresting
Many Greenland sharks are observed with a parasitic copepod (Ommatokoita elongata) attached to their corneas, which can impair their vision but may also be bioluminescent, potentially attracting prey.
Safety Information
Handle with care- Safety level: caution
- Venomous: No
- Edibility: not recommended
- Handling notes: While not venomous, Greenland sharks are large, powerful predators. Direct interaction should be avoided. Their fresh meat is toxic due to high urea and trimethylamine oxide content, which can cause 'shark sickness' if consumed without proper processing. This makes them inedible unless fermented and dried (e.g., hákarl).
Similar Species
Pacific Sleeper Shark
Somniosus pacificus
The Pacific sleeper shark inhabits the North Pacific Ocean and generally has a more pointed snout and larger dorsal fins relative to its body size compared to the Greenland shark. Genetic analysis is often required for definitive differentiation in overlapping regions.
Southern Sleeper Shark
Somniosus antarcticus
Found in the Southern Ocean. Morphologically very similar to the Greenland shark, but geographically distinct. Genetic studies have confirmed it as a separate species.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Chondrichthyes
- Order
- Squaliformes
- Family
- Somniosidae
- Genus
- Somniosus
- Species
- microcephalus
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