HOME

TheInfoList



OR:

''Thysanoteuthis rhombus'', also known as the diamond squid, diamondback squid, or rhomboid squid, is a large species of
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 ...
from the family Thysanoteuthidae which is found worldwide, throughout tropical and subtropical waters. ''T. rhombus'' is given its name for the appearance of the fins that run the length of the mantle. They are a fast growing species with a lifespan of approximately 1 year. The diamond squid is the only cephalopod species known to be
monogamous Monogamy ( ) is a relationship of two individuals in which they form a mutual and exclusive intimate partnership. Having only one partner at any one time, whether for life or serial monogamy, contrasts with various forms of non-monogamy (e.g. ...
. ''T. rhombus'' often preys on fish and other small cephalopods at varying water depths. This species is commercially fished in
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
, specifically 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 ...
and
Okinawa most commonly refers to: * Okinawa Prefecture, Japan's southernmost prefecture * Okinawa Island, the largest island of Okinawa Prefecture * Okinawa Islands, an island group including Okinawa itself * Okinawa (city), the second largest city in th ...
.


Description

''Thysanoteuthis rhombus'' are distinguishable by the presence of
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 ...
with two series of suckers, whereas the
tentacular 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 mainl ...
clubs have four. It lacks
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. ''T. rhombus'' is named for its
fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. F ...
s, which run in equal length along the mantle, giving the appearance of a
rhombus In plane Euclidean geometry, a rhombus (: rhombi or rhombuses) is a quadrilateral whose four sides all have the same length. Another name is equilateral quadrilateral, since equilateral means that all of its sides are equal in length. The rhom ...
. The species is able to grow up to in mantle length and a maximum weight of , although it averages around . The lifespan of ''T. rhombus'' is 1 year. Males mature at a mantle length between (170 to 200 days of age) while females mature at a mantle length between (230 to 250 days).


Biology

''T. rhombus'' typically inhabits open ocean waters of the subtropical and tropical locations with temperatures of . ''T. rhombus'' is not an active swimmer and propels itself slowly using its triangular fins, although the species is able to make powerful contractions of its mantle to escape predation ( jet propulsion). The diamond squid was found to be largely inactive or even die to sudden drops in temperatures, which went below This species feeds during the daytime at deep water levels and during the night at shallow water levels (
Diel vertical migration 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 ...
). ''T. rhombus'' are often found in pairs, but groups up to 20 have been recorded.


Ecology


Diet

In subsurface water levels, ''T. rhombus'' juveniles were found to feed on crustaceans, small cephalopods and
fishes A fish (: fish or fishes) is an aquatic, anamniotic, gill-bearing vertebrate animal with swimming fins and a hard skull, but lacking limbs with digits. Fish can be grouped into the more basal jawless fish and the more common jawed ...
. As adults, the stomach contents of the Diamond squid were found to consist mostly of nonactive fishes at water depths of .


Predation

The predators that feed on ''T. rhombus'' include various species of ommastrephid squids,
giant squid The giant squid (''Architeuthis dux'') is a species of deep-ocean dwelling 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, ...
(''Architeuthis dux''),
dolphinfish ''Coryphaena'' is a genus of marine ray-finned fishes known as the dolphinfishes, and is currently the only known genus in the family Coryphaenidae. The generic name is from Greek κορυφή (''koryphē'', "crown, top") and -αινα (-''aina ...
(''Coryphaena hippurus''), lancetfish (''Alepisaurus sp.''),
tuna A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...
,
swordfish The swordfish (''Xiphias gladius''), also known as the broadbill in some countries, are large, highly migratory predatory fish characterized by a long, flat, pointed bill. They are the sole member of the Family (biology), family Xiphiidae. They ...
(''Xiphias gladius''), snake mackerel (''Gempylus serpens''), and
shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...
s. Other predators include
cetaceans 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 ...
;
oceanic dolphin Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as the ...
s such as
rough-toothed dolphin The rough-toothed dolphin (''Steno bredanensis'') is a species of dolphin that can be found in deep warm and tropical waters around the world. The species was first described by Georges Cuvier in 1823. The genus name ''Steno'', of which this spe ...
s (''Steno bredanensis'') and
false killer whale The false killer whale (''Pseudorca crassidens'') is a species of oceanic dolphin that is the only extant representative of the genus ''Pseudorca''. It is found in oceans worldwide but mainly in tropical regions. It was first species descriptio ...
s (''Pseudorca crassidens''), along with
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 (''Physeter macrocephalus''), prey on diamond squid.


Reproduction

''T. rhombus'' has a relatively low population density, which has led to a unique situation among squids, where male and female couples of the same size remain together from their juvenile stage until death; this species is
monogamous Monogamy ( ) is a relationship of two individuals in which they form a mutual and exclusive intimate partnership. Having only one partner at any one time, whether for life or serial monogamy, contrasts with various forms of non-monogamy (e.g. ...
. The pairing of males and females occurs at an immature stage where mantle length is less than and pairs remain monogamous. Mating occurs in a head-to-head position, in which the male uses his
hectocotylus A hectocotylus (: hectocotyli) is one of the arms of male cephalopods that is specialized to store and transfer spermatophores to the female. Structurally, hectocotyli are muscular hydrostats. Depending on the species, the male may use it merel ...
to attach to the female's buccal membrane to transfer his
spermatophore A spermatophore, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especiall ...
s. Spawning is year round in tropical waters and lasts for 2–3 months, but in temperate regions spawning is restricted to summer or early autumn periods and warmer currents. ''T. rhombus'' is known to be an intermittent spawner and is known to have multiple spawning in succession. During spawning, females will produce secretions of gel-like substance from
nidamental gland Nidamental glands are internal organs found in some elasmobranchs and certain molluscs, including cephalopods (specifically Decapodiformes and nautiluses) and gastropod Gastropods (), commonly known as slugs and snails, belong to a large Ta ...
s, similar to the
Japanese flying squid The Japanese flying squid, Japanese common squid or Pacific flying squid, scientific name ''Todarodes pacificus'', is a squid of the family Ommastrephidae. This animal lives in the northern Pacific Ocean, in the area surrounding Japan, along the e ...
, that will enter the water and swell; this engorged secretion will then be molded by the female into a cylinder. Her oviductal glands will then begin to form two
mucous Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...
threads, each with one row of eggs, which will fuse into a single cord containing a double row of eggs in the mantle cavity. The fused egg-cord or mass is expelled into the water through the
funnel A funnel is a tube or pipe that is wide at the top and narrow at the bottom, used for guiding liquid or powder into a small opening. Funnels are usually made of stainless steel, aluminium, glass, or plastic. The material used in its constructi ...
where the eggs are fertilized with spermatozoa that were attached to the female's buccal membrane, in her
seminal receptacle Female sperm storage is a biological process and often a type of sexual selection in which sperm cells transferred to a female during mating are temporarily retained within a specific part of the reproductive tract before the oocyte, or egg, is fe ...
s. The fertilized egg cord is then wound onto the cylinder. A female can produce 8 to 12 egg-masses if properly utilizing its vitelline
oocyte An oocyte (, oöcyte, or ovocyte) is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ger ...
s.


Commercial value

''T. rhombus'' is targeted by growing
fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life or, more commonly, the site where such enterprise takes place ( a.k.a., fishing grounds). Commercial fisheries include wild fisheries and fish farm ...
in near southern and central Japan due to its firm and flavorful
flesh Flesh is any aggregation of soft tissues of an organism. Various multicellular organisms have soft tissues that may be called "flesh". In mammals, including humans, ''flesh'' encompasses muscles, fats and other loose connective tissues, ...
. The main fishing grounds are 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 ...
,
Okinawa Prefecture is the southernmost and westernmost prefecture of Japan. It consists of three main island groups—the Okinawa Islands, the Sakishima Islands, and the Daitō Islands—spread across a maritime zone approximately 1,000 kilometers east to west an ...
, and
Kagoshima Prefecture is a Prefectures of Japan, prefecture of Japan located on the island of Kyushu and the Ryukyu Islands. Kagoshima Prefecture has a population of 1,527,019 (1 February 2025) and has a geographic area of 9,187 Square kilometre, km2 (3,547 Square m ...
; the majority (~90%) of captures are located in the Sea of Japan and Okinawa. The Sea of Japan fishery runs from July to February, while the fishery in Okinawa runs primarily between November and April. To capture the diamond squid in the Sea of Japan, inshore trap nets and free-floating angling gear called "taru-nagashi" are used. In Okinawa, free-floating angling gear called "Hata-nagashi" is used for capture. "Taru-nagashi" is gear that consists of a vertical weighted
long line Long line or longline may refer to: *'' Long Line'', an album by Peter Wolf *Long line (topology), or Alexandroff line, a topological space * Long line (telecommunications), a transmission line in a long-distance communications network *Longline fi ...
with two or three artificial lures and with two or three rows of stainless steel
hook A hook is a tool consisting of a length of material, typically metal, that contains a portion that is curved/bent back or has a deeply grooved indentation, which serves to grab, latch or in any way attach itself onto another object. The hook's d ...
s. At the other end of the line, an orange fluorescent
buoy A buoy (; ) is a buoyancy, floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. History The ultimate origin of buoys is unknown, but by 1295 a seaman's manual referred to navig ...
lays on its side on the surface until a squid hooks onto the line, which causes the buoy to stand up and alert the fisherman. The caught squid are pulled up by hand or by using a
winch A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension (physics), tension of a rope or wire rope (also called "cable" or "wire cable"). In its simplest form, it consists of a Bobb ...
, so it is primarily used during the day. "Hata-nagashi" is gear that was adapted for the oceanographic conditions of Okinawa Prefecture. It has several artificial lures attached to a longer main line than those used in the Sea of Japan. The line is attached to several buoys and a flag at the surface. This gear lead to the increase of catches of ''T. rhombus''.


See also

*
Cephalopod size Cephalopods, which include squids and octopuses, vary enormously in size. The smallest are only about long and weigh less than at maturity, while the giant squid can exceed in length and the colossal squid weighs close to half a tonne (), makin ...
*
Humboldt squid The Humboldt squid (''Dosidicus gigas''), also known as jumbo squid or jumbo flying squid, is a large, predatory squid living in the eastern Pacific Ocean. It is the Monotypic taxon, only known species of the genus ''Dosidicus'' of the subfamily ...
, another large species with its own dedicated fishery


References

* Tokalau, T. 2014
Giant squid market
''The Fiji Times Online'', 5 July 2014.
Giant potential: giant squid fishing could be next big Pacific market
Australia Network News, 10 July 2014.


External links


Tree of Life web project: ''Thysanoteuthis rhombus''
{{Taxonbar, from=Q3204576, from2=Q1994083 Cranchioidea Molluscs of the Atlantic Ocean Molluscs of the Indian Ocean Molluscs of the Pacific Ocean Sushi Cephalopods described in 1857 Taxa named by Franz Hermann Troschel