The Pacific sleeper shark (''Somniosus pacificus'') is a sleeper shark of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Somniosidae The Somniosidae are a family of sharks in the order Squaliformes, commonly known as sleeper sharks. The common name ''"sleeper shark"'' comes from their slow swimming, low activity level, and perceived non-aggressive nature. Distribution and hab ...

, found in the North Pacific on

continental shelves A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

and slopes in

Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...

and

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

waters between

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

s 70°N and 22°N, from the surface to deep. Records from southern oceans are likely misidentifications of

relatives Relatives can refer to: * Kinship * ''Relatives'' (1985 film), a 1985 Australian movie * ''Relatives'' (2006 film), a 2006 Hungarian movie * "Relatives", a song by Irving Berlin Irving Berlin (born Israel Beilin; yi, ישראל ביילין ...

. Its length is up to , although it could possibly reach lengths in excess of .

Feeding habits

Pacific sleeper sharks, which are thought to be both predators and scavengers, can glide through the water with little body movement and little hydrodynamic noise, making them successful stealth predators. They feed by means of suction and cutting of their prey. They have large mouths that can essentially inhale prey and their teeth cut up any pieces that are too large to swallow. They show a characteristic rolling motion of the head when feeding. Only in

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

has the shark's diet been studied - most sharks' stomachs contain remains of giant Pacific octopus. They are also known to feed on bottom-dwelling teleost fishes, as well as soles,

flounder Flounders are a group of flatfish species. They are demersal fish, found at the bottom of oceans around the world; some species will also enter estuaries. Taxonomy The name "flounder" is used for several only distantly related species, thou ...

s, Alaska pollock, rockfishes,

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

s, hermit crabs, and even marine

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastro ...

s. Larger Pacific sleeper sharks are also found to feed on fast-swimming prey such as

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

s, Pacific salmon, and

harbor porpoise The harbour porpoise (''Phocoena phocoena'') is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar ...

s. The diet of the Pacific sleeper shark seems to broaden as they increase in size. For example, a 3.7-m female shark found off Trinidad, California was found to have fed mostly on

giant squid The giant squid (''Architeuthis dux'') is a species of deep-ocean dwelling squid in the family Architeuthidae. It can grow to a tremendous size, offering an example of abyssal gigantism: recent estimates put the maximum size at around Trace ...

. Sleeper sharks found in Alaskan waters from seem to feed mostly on flounder, pollock, and

cephalopods A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, an ...

, while sleeper sharks long seem to consume teleosts and cephalopods, as well as

marine mammal Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their reli ...

s. A recent study in the Gulf of Alaska suggests that sleeper sharks may prey on juvenile

Steller sea lion The Steller sea lion (''Eumetopias jubatus''), also known as the Steller's sea lion and northern sea lion, is a near-threatened species of sea lion in the northern Pacific. It is the sole member of the genus ''Eumetopias'' and the largest of t ...

Reproduction

Very little is known about the early life of Pacific sleeper sharks. They are believed to produce eggs that hatch inside the female's body (reproduction is

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

), but gestation time is unknown and litter sizes are thought to be about 10 pups. Its length at birth is about or less.

Size

The average mature size is and . The largest Pacific sleeper shark verified in size measured long and weighed , although it could possibly reach or more.Castro, José I., ''The Sharks of North America''. Oxford University Press (2011), In 1989, an enormous Pacific sleeper shark was attracted to a bait in deep water outside

Tokyo Bay is a bay located in the southern Kantō region of Japan, and spans the coasts of Tokyo, Kanagawa Prefecture, and Chiba Prefecture. Tokyo Bay is connected to the Pacific Ocean by the Uraga Channel. The Tokyo Bay region is both the most populous a ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, and filmed. The shark was estimated by Eugenie Clark to be about long.

Adaptations

Due to living in frigid depths, the sleeper shark's liver oil does not contain squalene, which would solidify into a dense, nonbuoyant mass. Instead, the low-density compounds in the sharks' liver are diacylglyceryl ethers and

triacylglycerol A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride''). Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...

, which maintain their fluidity even at the lowest temperatures. Also, they store very little

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...

in their skin (like many deep sea sharks), but like other elasmobranchs, have high concentrations of urea and

trimethylamine oxide Trimethylamine ''N''-oxide (TMAO) is an organic compound with the formula (CH3)3NO. It is in the class of amine oxides. Although the anhydrous compound is known, trimethylamine ''N''-oxide is usually encountered as the dihydrate. Both the anhydro ...

(nitrogenous waste products) in their tissues as

osmoprotectant Osmoprotectants or compatible solutes are small organic molecules with neutral charge and low toxicity at high concentrations that act as osmolytes and help organisms survive extreme osmotic stress. Osmoprotectants can be placed in three chemical c ...

s and to increase their

buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...

. Trimethylamine oxide also serves to counteract the

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

- destabilizing tendencies of

and pressure. Its presence in the tissues of both elasmobranch and teleost fish has been found to increase with depth. Because food is relatively scarce on the deep sea floor, the sleeper shark is able to store food in its capacious stomach. The sleeper shark's jaws are able to produce a powerful bite due to their short and transverse shape. The upper jaw teeth of the sleeper shark are spike-like, while the lower jaw teeth are oblique cusps and overlapping bases. This arrangement allows grasping and sawing of food too large to swallow. Pacific sleeper sharks have a short

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

, which allows them to store energy for fast and violent bursts of energy to catch prey. In 2015 a pacific sleeper shark was filmed near the Solomon Islands underneath an active volcano. The shark is able to survive in water with a high temperature and acidity.

Known predators

Sleeper sharks are preyed on by the offshore ecotype of

killer whale The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus ''Orcinus'' and is recognizable by its black-and-white pa ...

off British Columbia. In addition, like the

Greenland shark The Greenland shark (''Somniosus microcephalus''), also known as the gurry shark, grey shark, or by the Kalaallisut name ''eqalussuaq'', is a large shark of the family Somniosidae ("sleeper sharks"), closely related to the Pacific and southern s ...

, the parasitic

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

Ommatokoita elongata ''Ommatokoita'' is a monotypic genus of copepods, the sole species being ''Ommatokoita elongata''. However, a specimen has been found on the skin of '' Etmopterus princeps'', which has been assigned to the genus but not the species. ''Ommatokoit ...

'' can often be observed consuming the shark's corneal tissue.

References

;General references * * * Castro, Jose. "Pacific Sleeper Sharks (Somniosus pacificus)." Conservation Science Institute. 1983

* Martin, R. A. "Pacific Sleeper Shark Bibliography." Biology of Sharks and Reys. ReefQuest Centre for Shark Researc

* "Megalodon caught on tape." My Paranormal Life. Google

(Erroneously-labelled footage of a sleeper shark) * Carroll, Amy. "Sleeper Sharks: Awake and Hungry Sleeper sharks Not Culprits in Sea Lion Declines." Alaska Fish and Wildlife News. 1999. Alaska Department of Fish and Gam

External links

*
ORCA Video of a sleeper shark
{{DEFAULTSORT:Pacific sleeper shark Somniosus Fish of the Pacific Ocean Fish of the Arctic Ocean Fish of Canada Fish of Japan Fish of Mexican Pacific coast Fish of Russia Fish of the Western United States Fauna of Alaska Fauna of California Fauna of the Baja California Peninsula Marine fish of Asia Western North American coastal fauna Fish described in 1944 Least concern biota of Asia Least concern biota of North America