Gonatidae
Encyclopedia
The Gonatidae, also known as armhook squid, are a family
of moderately-sized squid
. The family contains approximately 19 species
in three genera
, widely distributed and plentiful in cold boreal waters of the Pacific Ocean
. At least one species is known from Antarctic waters, and two from the North Atlantic.
Morphologically, armhook squid are fairly uniform: all species are characterised by the suckers of their arm
s, 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), it is only the females who 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 (Gonatus) pyros), possesses photophore
s; these are located on the ventral periphery of the eye
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 percent of the mantle
length, to reniform and about 30 percent of the mantle length. Of moderate size, these squid range in size from 11 centimetres to 40 centimetres—most species are 25 centimetres or less. Females are somewhat larger than males.
These squid are pelagic
, associated with the continental shelf
and may roam as deep as 4,500 metres or more, depending on the species. Their habits are poorly studied, but the squid are thought to undertake diel
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 (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 obeserved have been seen to deposit eggs on the sea floor than 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 Gonatidae family or if it is particular to this species.
Prey items include both benthic
and pelagic species, including; smaller fish
such as sculpin
s and juvenile pollock
, crustacean
s including euphausiids and amphipods, and other squid. Cannibalism
is also known to occur among the Gonatidae.
Cetaceans are important predators of gonatids; Baird's beaked whale, the narwhal
, the short-finned pilot whale
, Dall's porpoise
and sperm whale
s are all known to feed upon them. Other predators include large seabird
s, Northern fur seal
s and elephant seal
s, large fish such as grenadier
s, halibut
and several species of salmon
. In far southern waters, Weddell seal
s and Southern fur seals as well as several species of albatross
and penguin
feed upon Gonatus (Gonatus) antarcticus.
The species listed above with an asterisk (* ) is questionable and needs further study to determine if it is a valid species or a synonym.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of moderately-sized squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
. The family contains approximately 19 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in three genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, widely distributed and plentiful in cold boreal waters of the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. At least one species is known from Antarctic waters, and two from the North Atlantic.
Physical description
Cephalopod arm
A cephalopod arm is distinct from a tentacle, though the terms are often used interchangeably.Generally, cephalopod arms have suckers along most of their length, as opposed to tentacles, which have suckers only near their ends. Octopuses have eight arms and no tentacles, while squid and cuttlefish...
s, 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
Magister Armhook Squid
The Magister Armhook Squid , also known as the Commander Squid or Schoolmaster Gonate Squid, is a medium-sized squid in the family Gonatidae. It is found in cold, high latitude waters of the North Pacific where it is among the most numerous squid species recorded.There are three recognised...
(Berryteuthis magister), it is only the females who possess hooks. Species of the genus Gonatus
Gonatus
Gonatus is a genus of squid in the family Gonatidae, comprising twelve species, and therefore containing the most species in the family. Adult squid belonging to species in this genus are notable for their lack of tentacles.-Species:...
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 (Gonatus) pyros), possesses photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...
s; these are located on the ventral periphery of the eye
Cephalopod eye
Cephalopods, as active marine predators, possess sensory organs specialized for use in aquatic conditions. They have a camera-type eye, which consists of a lens projecting an image onto a retina. Unlike the vertebrate camera eye, the cephalopods' form as invaginations of the body surface , and...
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 percent of the mantle
Mantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
length, to reniform and about 30 percent of the mantle length. Of moderate size, these squid range in size from 11 centimetres to 40 centimetres—most species are 25 centimetres or less. Females are somewhat larger than males.
Life history
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
, associated with the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
and may roam as deep as 4,500 metres or more, depending on the species. Their habits are poorly studied, but the squid are thought to undertake diel
Diel vertical migration
Diel vertical migration, also known as diurnal vertical migration, is a pattern of movement that some organisms living in the ocean and in lakes undertake each day. Usually organisms move up to the epipelagic zone at night and return to the mesopelagic zone of the oceans or to the hypolimnion zone...
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 (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 obeserved have been seen to deposit eggs on the sea floor than leave the eggs to hatch on their own. Five female Gonatus onyx squids have been observed in Monterey Canyon
Monterey Canyon
Monterey Canyon, or Monterey Submarine Canyon, is a submarine canyon in Monterey Bay, California. It is the subject of ongoing study by the scientists at the Monterey Bay Aquarium Research Institute, the Moss Landing Marine Laboratories, and other oceanographic institutions.Monterey Canyon begins...
dragging a membrane sack containing 2,000 to 3,000 developing eggs. It is uncertain if this behavior extends to other members of the Gonatidae family or if it is particular to this species.
Prey items include both benthic
Benthos
Benthos is the community of organisms which live on, in, or near the seabed, also known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.Many organisms...
and pelagic species, including; smaller fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
such as sculpin
Sculpin
A Sculpin is a fish that belongs to the order Scorpaeniformes, suborder Cottoidei and superfamily Cottoidea, that contains 11 families, 149 genera, and 756 species...
s and juvenile pollock
Pollock
Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...
, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s including euphausiids and amphipods, and other squid. Cannibalism
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...
is also known to occur among the Gonatidae.
Cetaceans are important predators of gonatids; Baird's beaked whale, the narwhal
Narwhal
The narwhal, Monodon monoceros, is a medium-sized toothed whale that lives year-round in the Arctic. One of two living species of whale in the Monodontidae family, along with the beluga whale, the narwhal males are distinguished by a characteristic long, straight, helical tusk extending from their...
, the short-finned pilot whale
Short-finned Pilot Whale
The Short-finned Pilot Whale is one of the two species of cetacean in the genus Globicephala. It is part of the oceanic dolphin family , though its behaviour is closer to that of the larger whales....
, Dall's porpoise
Dall's Porpoise
Dall's porpoise is a species of porpoise found on the North Pacific. It came to worldwide attention in the 1970s when it was disclosed for the first time to the public that salmon fishing trawls were killing a lot, thousands of Dall's porpoises and other cetaceans each year by accidentally...
and sperm whale
Sperm Whale
The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...
s are all known to feed upon them. Other predators include large seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s, Northern fur seal
Northern Fur Seal
The Northern fur seal 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 and the only species in the genus Callorhinus.-Physical description:Northern fur seals have extreme sexual dimorphism, with males...
s and elephant seal
Elephant seal
Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the northern elephant seal and the southern elephant seal . Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered...
s, large fish such as grenadier
Rattail
Grenadiers or rattails are generally large, brown to black gadiform marine fish of the family Macrouridae...
s, halibut
Halibut
Halibut is a flatfish, genus Hippoglossus, from the family of the right-eye flounders . Other flatfish are also called halibut. The name is derived from haly and butt , for its popularity on Catholic holy days...
and several species of salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
. In far southern waters, Weddell seal
Weddell Seal
The Weddell seal , is a relatively large and abundant true seal with a circumpolar distribution surrounding Antarctica. Weddell seals have the most southerly distribution of any mammal, with a habitat that extends as far south as McMurdo Sound...
s and Southern fur seals as well as several species of albatross
Albatross
Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
and penguin
Penguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...
feed upon Gonatus (Gonatus) antarcticus.
Species
- Genus BerryteuthisBerryteuthisBerryteuthis is a genus of squid in the family Gonatidae, comprising two known species. The two members differ greatly in size, with B. anonychus and B. magister reaching mature mantle lengths of 10 cm and 40 cm respectively...
- Berryteuthis anonychus, Sparkling Enope Squid or Firefly Squid
- Berryteuthis magister
- Berryteuthis magister magister, Magister Armhook Squid
- Berryteuthis magister nipponensis
- Berryteuthis magister shevtsovi
- Genus Eogonatus
- Eogonatus tinro
- Genus Gonatopsis
- Subgenus Boreoteuthis
- Gonatopsis borealis, Boreopacific Armhook Squid
- Subgenus Gonatopsis
- Gonatopsis japonica
- Gonatopsis makko, Makko Armhook Squid
- Gonatopsis octopedatus
- Gonatopsis okutanii *
- Subgenus Boreoteuthis
- Genus GonatusGonatusGonatus is a genus of squid in the family Gonatidae, comprising twelve species, and therefore containing the most species in the family. Adult squid belonging to species in this genus are notable for their lack of tentacles.-Species:...
- 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 (