The Gonatidae, also known as armhook squid, are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of moderately sized

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

. The family contains about 19

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

in three

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

, widely distributed and plentiful in cold boreal waters of the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

. At least one species is known from

Antarctic The Antarctic (, ; commonly ) is the polar regions of Earth, polar region of Earth that surrounds the South Pole, lying within the Antarctic Circle. It is antipodes, diametrically opposite of the Arctic region around the North Pole. The Antar ...

waters, and two from the

North Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for ...

. The genus '' Eogonatus'' was created for the species known as '' Eogonatus tinro'' because it did not have hooks on the

tentacular club All cephalopods possess flexible limbs extending from their heads and surrounding their cephalopod beak, beaks. These appendages, which function as muscular hydrostats, have been variously termed arms, legs or tentacles. Description In ...

and it has 5 rows of teeth on the

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...

. Molecular studies in allozymes and

mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

have indicated that this species nests within the genus '' Gonatus'', although other authorities treat it as a

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

of '' Gonatopsis okutanii''.

Description

Morphologically, armhook squid are fairly uniform: all species are characterised by the suckers of their arms, which are arranged in four rows (series) rather than the typical count of two. In most species, the arm's two mesial rows of suckers have been modified into hooks and the tentacular clubs—which are covered with many irregular rows of tiny suckers—may possess an enlarged central hook, with or without several smaller hooks. In the magister armhook squid (''Berryteuthis magister''), only the females possess hooks. Species of the genus '' Gonatus'' differ from the rest of the family (and from most squid) by their lack of tentacles as adults. Only one species, the fiery armhook squid (''Gonatus pyros''), possesses

photophore A photophore is a specialized anatomical structure found in a variety of organisms that emits light through the process of boluminescence. This light may be produced endogenously by the organism itself (symbiotic) or generated through a mut ...

s; these are located on the ventral periphery of the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

s. Gonatids typically have muscular, cylindrical bodies with very soft, reddish to purplish-brown skin. The arms are thick and capable; the fins vary in shape and size, from sagittate and about 50% of the mantle length, to reniform and about 30% of the mantle length. Of moderate size, these squid range in size from 11 to 40 cm—most species are 25 cm or less. Females are somewhat larger than males.

Life history

These squid are

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

, associated with the

continental shelf 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 islan ...

and may roam as deep as 4,500 m or more, depending on the species. Their habits are poorly studied, but the squid are thought to undertake

diel Diel vertical migration (DVM), also known as diurnal vertical migration, is a pattern of movement used by some organisms, such as copepods, living in the ocean and in lakes. The adjective "diel" ( IPA: , ) comes from , and refers to a 24-hour ...

migration; by day, the squid remain in the blackness of the depths in midwater. By night, they ascend to the upper layers of the water column to feed by starlight. One species, however, '' Gonatopsis octopedatus'', has curiously recurved arms, suggesting a benthic existence. Little is known about the reproductive cycle of armhook squid. Most squid species whose reproduction has been observed have been seen to deposit eggs on the sea floor, then leave the eggs to hatch on their own. Five female ''Gonatus onyx'' squids have been observed in Monterey Canyon dragging a membrane sack containing 2,000 to 3,000 developing eggs. It is uncertain if this behavior extends to other members of the family Gonatidae or if it is particular to this species. Prey items include both

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

and pelagic species, including smaller

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

, such as

sculpin A sculpin is a type of fish that belongs to the superfamily Cottoidea in the order Perciformes.Kane, E. A. and T. E. Higham. (2012)Life in the flow lane: differences in pectoral fin morphology suggest transitions in station-holding demand acros ...

s and juvenile

pollock Pollock or pollack (pronounced ) is the common name used for either of the two species of North Atlantic ocean, marine fish in the genus ''Pollachius''. ''Pollachius pollachius'' is referred to as "pollock" in North America, Ireland and the Unit ...

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, including euphausiids and amphipods, and other squid.

Cannibalism Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is also well document ...

is also known to occur among the Gonatidae.

Cetacean Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...

s are important predators of gonatids; Baird's beaked whale, the

narwhal The narwhal (''Monodon monoceros'') is a species of toothed whale native to the Arctic. It is the only member of the genus ''Monodon'' and one of two living representatives of the family Monodontidae. The narwhal is a stocky cetacean with a ...

, the

short-finned pilot whale The short-finned pilot whale (''Globicephala macrorhynchus'') is one of the two species of cetaceans in the genus ''Pilot whale, Globicephala'', which it shares with the long-finned pilot whale (''G. melas''). It is part of the oceanic dolphin ...

Dall's porpoise Dall's porpoise (''Phocoenoides dalli'') is a species of porpoise endemic to the North Pacific. It is the largest of porpoises and the only member of the genus ''Phocoenoides''. The species is named after American naturalist William Healey Dall, ...

, and

sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the Genus (biology), genus ''Physeter'' and one of three extant species in the s ...

s are all known to feed upon them. Other predators include large

seabird Seabirds (also known as marine birds) are birds that are adaptation, adapted to life within the marine ecosystem, marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent ...

northern fur seal The northern fur seal (''Callorhinus ursinus'') is an eared seal found along the north Pacific Ocean, the Bering Sea, and the Sea of Okhotsk. It is the largest member of the fur seal subfamily (Arctocephalinae) and the only living species in the ...

elephant seal Elephant seals or sea elephants are very large, oceangoing earless seals in the genus ''Mirounga''. Both species, the northern elephant seal (''M. angustirostris'') and the southern elephant seal (''M. leonina''), were hunted to the brink of ...

s, and large fish, such as

grenadier A grenadier ( , ; derived from the word ''grenade'') was historically an assault-specialist soldier who threw hand grenades in siege operation battles. The distinct combat function of the grenadier was established in the mid-17th century, when ...

halibut Halibut is the common name for three species of flatfish in the family of right-eye flounders. In some regions, and less commonly, other species of large flatfish are also referred to as halibut. The word is derived from ''haly'' (holy) and ...

and several species of

salmon Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...

. In far southern waters,

Weddell seal The Weddell seal (''Leptonychotes weddellii'') is a relatively large and abundant Earless seal, true seal with a Subantarctic, circumpolar distribution surrounding Antarctica. The Weddell seal was discovered and named in the 1820s during expediti ...

s and southern fur seals, as well as several species of

albatross Albatrosses, of the biological family Diomedeidae, are large seabirds related to the procellariids, storm petrels, and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Paci ...

and

penguin Penguins are a group of aquatic flightless birds from the family Spheniscidae () of the order Sphenisciformes (). They live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, is equatorial, with a sm ...

, feed upon '' Gonatus antarcticus''.

Species

*Genus '' Berryteuthis'' **'' Berryteuthis anonychus'', minimal armhook squid **'' Berryteuthis magister'' ***'' Berryteuthis magister magister'', magister armhook squid ***'' Berryteuthis magister nipponensis'' ***'' Berryteuthis magister shevtsovi'' *Genus '' Gonatopsis'' **Subgenus ''Boreoteuthis'' ***'' Gonatopsis borealis'', boreopacific armhook squid **Subgenus ''Gonatopsis'' ***'' Gonatopsis japonicus'' ***'' Gonatopsis makko'', Makko armhook squid ***'' Gonatopsis octopedatus'' ***'' Gonatopsis okutanii'' * *Genus '' Gonatus'' **'' Gonatus antarcticus'' **'' Gonatus berryi'', Berry armhook squid **'' Gonatus californiensis'', California armhook squid **'' Gonatus fabricii'', boreoatlantic armhook squid **'' Gonatus kamtschaticus'' **'' Gonatus madokai'', Madokai armhook squid **'' Gonatus onyx'', clawed armhook squid or black-eyed squid **'' Gonatus oregonensis'', Oregon armhook squid **'' Gonatus pyros'', fiery armhook squid **'' Gonatus steenstrupi'', Atlantic armhook squid **'' Gonatus ursabrunae'', brown bear armhook squid The species listed above with an asterisk (*) is questionable and needs further study to determine if it is a valid species or a synonym.

References

External links

Tree of Life web project: GonatidaeGonatidae discussion forum at TONMO.comSmall-clawed armhook quid subduing and killing an owlfish
video from the Monterey Bay Aquarium Research Institute. * {{Authority control Oegopsida Cephalopod families Taxa named by William Evans Hoyle