''Gonatopsis japonicus'' is a species of

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 ...

from 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 ...

Gonatidae The Gonatidae, also known as armhook squid, are a family of moderately sized squid. The family contains about 19 species in three genera, widely distributed and plentiful in cold boreal waters of the Pacific Ocean. At least one species is known f ...

. This species is restricted to the western North Pacific in the seas around the

Japanese Archipelago The Japanese archipelago (Japanese: 日本列島, ''Nihon rettō'') is a group of 6,852 islands that form the country of Japan, as well as the Russian island of Sakhalin. It extends over from the Sea of Okhotsk in the northeast to the East Chin ...

Description

''Gonatopsis japonicus'' is a squid with a slender, muscular mantle. It is relatively large with thin fins and a long, pointed tail. The head is wider than the opening of the mantle. It has robust

arms Arms or ARMS may refer to: *Arm or arms, the upper limbs of the body Arm, Arms, or ARMS may also refer to: People * Ida A. T. Arms (1856–1931), American missionary-educator, temperance leader Coat of arms or weapons *Armaments or weapons **Fi ...

that are armed with heavy hooks. These arms are of different lengths, the longest being just over half the length of the mantle. There are five rows of teeth on the radula.

Tentacles In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

are absent in adults. It is a large species that grows to a mantle length of 620mm.

Distribution

''Gonatopsis japonicus'' is restricted to the western North Pacific in the

Sea of Japan The Sea of Japan is the marginal sea between the Japanese archipelago, Sakhalin, the Korean Peninsula, and the mainland of the Russian Far East. The Japanese archipelago separates the sea from the Pacific Ocean. Like the Mediterranean Sea, it h ...

north to the southern

Okhotsk Sea The Sea of Okhotsk ( rus, Охо́тское мо́ре, Ohótskoye móre ; ja, オホーツク海, Ohōtsuku-kai) is a marginal sea of the western Pacific Ocean. It is located between Russia's Kamchatka Peninsula on the east, the Kuril Islands ...

and it may also occur off the eastern coast of Japan. It has also been reported from the

Kuril Islands The Kuril Islands or Kurile Islands (; rus, Кури́льские острова́, r=Kuril'skiye ostrova, p=kʊˈrʲilʲskʲɪjə ɐstrɐˈva; Japanese: or ) are a volcanic archipelago currently administered as part of Sakhalin Oblast in the ...

east to the central and eastern

Bering Sea The Bering Sea (, ; rus, Бе́рингово мо́ре, r=Béringovo móre) is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasses on Earth: Eurasia and The Ameri ...

Habitat and biology

''Gonatopsis japonicus'' appears to mature at a relatively small size of approximately 150 mm in mantle length, and this is indicated by the development of hooks on the arms and the drak pigmentation of the

beak The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for food ...

. This species can be found from the

epipelagic The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...

zone down into the

mesopelagic The mesopelagic zone (Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light, and begins ...

and bathypelagic zones, with specimens having been taken from midwater at depths from near the surface to 1000m and from the sea bed at depths from 400m to 2000m. In the Sea of Japan this species was most abundant in the upper 140 m, and its abundance rapidly declined with increasing depth. The regular capturing of juveniles and young adults in the surface layers suggests that this species is an active vertical migrant, it further suggests that its

ontogenetic Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the st ...

descent takes place relatively late in its life cycle. Most of the specimens taken up to now have been immature or they were newly mature. In the Okhotsk Sea measurements of mature and pre-spawning males from the mesopelagic and bathypelagic zones gave mantle lengths which ranged from 278mm to 478mm, while immature and maturing females mantle lengths ranged from 398mm to 582mm. The largest specimen taken had a mantle length of 620mm. As the squid matures the muscle tissues in its body become increasingly gelatinous.

Human use

''Gonatopsis japonicus'' is not utilised by humans.

References

{{Taxonbar, from=Q2329689 Squid Molluscs described in 1969