Squid
Overview
Squid are cephalopod
s 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, tentacle
s. Squid are strong swimmers and certain species can 'fly' for short distances out of the water.
Squid have differentiated from their ancestral molluscs such that the body plan has been condensed antero-posteriorly and extended dorso-ventrally.
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a 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...
, and arms
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...
. Squid, like cuttlefish
Cuttlefish
Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....
, have eight arms
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...
arranged in pairs and two, usually longer, tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s. Squid are strong swimmers and certain species can 'fly' for short distances out of the water.
Squid have differentiated from their ancestral molluscs such that the body plan has been condensed antero-posteriorly and extended dorso-ventrally.
Unanswered Questions
Discussions
Encyclopedia
Squid are cephalopod
s 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, tentacle
s. Squid are strong swimmers and certain species can 'fly' for short distances out of the water.
of the ancestor is modified into a complex set of tentacles and highly developed sense organs, including advanced eyes similar to those of vertebrate
s.
The ancestral shell has been lost, with only an internal gladius, or pen, remaining. The pen is a feather-shaped internal structure that supports the squid's mantle
and serves as a site for muscle attachment. It is made of a chitin
-like substance.
The main body mass is enclosed in the mantle
, which has a swimming fin along each side. These fins, unlike in other marine organisms, are not the main source of locomotion in most species.
The skin is covered in chromatophore
s, which enable the squid to change color to suit its surroundings, making it practically invisible. The underside is also almost always lighter than the topside, to provide camouflage
from both prey and predator.
Under the body are openings to the mantle cavity, which contains the gills (ctenidia) and openings to the excretory and reproductive system
s. At the front of the mantle cavity lies the siphon, which the squid uses for locomotion via precise jet propulsion
. In this form of locomotion, water is sucked into the mantle cavity and expelled out of the siphon in a fast, strong jet. The direction of the siphon can be changed, to suit the direction of travel.
Inside the mantle cavity, beyond the siphon, lies the visceral mass, which is covered by a thin, membranous epidermis
. Under this are all the major internal organs.
, which may be up to 1 mm (0.04 inches) in diameter in some larger species, innervates
the mantle and controls part of the jet propulsion system.
As cephalopods, squid exhibit relatively high intelligence among invertebrates. For example, groups of Humboldt squid
hunt cooperatively, using active communication. (See Cephalopod intelligence
.)
is hidden from view by a pair of white nidamental gland
s, which lie anterior to the gills. There are also red-spotted accessory nidamental glands. Both organs are associated with food manufacture and shells for the eggs. Females also have a large translucent ovary
, situated towards the posterior of the visceral mass.
Males do not possess these organs, but instead have a large testis in place of the ovary, and a spermatophoric gland and sac. In mature males, this sac may contain spermatophore
s, which are placed inside the female's mantle during mating.
Shallow water species of the continental shelf
and epipelagic/mesopelagic
zones are characterised by the presence of hectocotyli, specially modified arms used to fertilise the female's eggs. Most deep sea squid lack hectocotyli and have longer penis
es; Ancistrocheiridae and Cranchiinae
are exceptions. Giant squid
of the genus Architeuthis are unusual in that they possess both a large penis and modified arm tips, although it is uncertain whether the latter are used for spermatophore transfer. Penis elongation has been observed in the deep water species Onykia ingens; when erect, the penis may be as long as the mantle, head and arms combined. As such, deep water squid have the greatest known penis length relative to body size of all mobile animals, second in the entire animal kingdom only to certain sessile barnacle
s.
is found roughly in the midpoint of the visceral mass. From there, the bolus
moves into the caecum for digestion. The caecum, a long, white organ, is found next to the ovary or testis. In mature squid, more priority is given to reproduction such that the stomach and caecum often shrivel up during the later life stages. Finally, food goes to the liver
(or digestive gland), found at the siphon end, for absorption. Solid waste is passed out of the rectum
. Beside the rectum is the ink sac, which allows a squid to rapidly discharge black ink into the mantle cavity.
s. Two branchial heart
s feed the gills, each surrounding the larger systemic heart that pumps blood around the body. Squid blood contains the copper
-rich protein
hemocyanin
for transporting oxygen
. The faintly greenish hearts are surrounded by the renal sacs - the main excretory system. The kidney
s are difficult to identify and stretch from the hearts (located at the posterior side of the ink sac) to the liver. The systemic heart is made of three chambers, a lower ventricle
and two upper auricles.
containing many suckers along the edge. These tentacles do not grow back if severed. In the mature male, one basal half of the left ventral tentacle is hectocotylised
— and ends in a copulatory pad rather than suckers. It is used for intercourse.
The mouth is equipped with a sharp horny beak mainly made of chitin
and cross-linked proteins, and is used to kill and tear prey into manageable pieces. The beak is very robust, but does not contain minerals, unlike the teeth and jaws of many other organisms, including marine species.
Captured whale
s often have indigestible squid beaks in their stomachs. The mouth contains the radula
(the rough tongue common to all molluscs except bivalvia
).
The eyes, on either side of the head, each contain a hard lens
. The image is focused by changing the position of the lens, as in a camera
or telescope
, rather than changing the shape of the lens, as in the human eye
.
Squid appear to have limited hearing.
The majority are no more than 60 centimetres (23.6 in) long, although the giant squid
may reach 13 metres (42.7 ft).
In 1978, sharp, curved claws on the suction cups of squid tentacles cut up the rubber coating on the hull of the USS Stein
. The size suggested the largest squid known at the time.
In 2003, a large specimen of an abundant but poorly understood species, Mesonychoteuthis hamiltoni (the Colossal Squid
), was discovered. This species may grow to 14 metres (45.9 ft) in length, making it the largest invertebrate
. Squid have the largest eyes in the animal kingdom. Giant squid are featured in literature and folklore with a frightening connotation. The Kraken
is a legendary tentacled monster possibly based on sightings of real giant squid.
In February 2007, a New Zealand fishing vessel caught a Colossal Squid
weighing 495 kilograms (1,091.3 lb) and measuring around 10 metres (32.8 ft) off the coast of Antarctica. This specimen represents the largest cephalopod to ever be scientifically documented.
Squid are members of the class Cephalopod
a, subclass Coleoidea
, order Teuthida, of which there are two major suborders, Myopsina
and Oegopsina
(including giant squid
s like Architeuthis dux). Teuthida is the largest cephalopod order with around 300 species classified into 29 families.
The order Teuthida is a member of the superorder Decapodiformes
(from the Greek
for "ten legs"). Two other orders of decapodiform cephalopods are also called squid, although they are taxonomically
distinct from Teuthida and differ recognizably in their gross anatomical features. They are the bobtail squid
of order Sepiolida and the ram's horn squid
of the monotypic order Spirulida
. The vampire squid
, however, is more closely related to the octopuses than to any squid.
, the cephalopod catch for 2002 was 3173272 tonnes (6,995,867,236.5 lb). Of this, 2,189,206 tonnes, or 75.8 percent, was squid. The following table lists the squid species fishery catches which exceeded 10000 tonnes (22,046,226.2 lb) in 2002.
Many species are popular as food in cuisines as diverse as Chinese
, Greek, Turkish
, Japanese
, Portuguese
, Italian
, Spanish
, Korean, Indian
, Vietnamese, and Filipino.
In English
-speaking countries, squid as food is often marketed using the Italian word calamari. Squid are found abundantly in certain areas, and provide large catches for fisheries
. The body can be stuffed whole, cut into flat pieces or sliced into rings. The arms, tentacles and ink are also edible; in fact, the only parts that are not eaten are the beak
and gladius
(pen). Squid is a good food source for zinc
, manganese
and high in the recommended daily intake of copper
, selenium
, vitamin B12
, and riboflavin
.
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a 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...
, and arms
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...
. Squid, like cuttlefish
Cuttlefish
Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....
, have eight arms
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...
arranged in pairs and two, usually longer, tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s. Squid are strong swimmers and certain species can 'fly' for short distances out of the water.
Modification from ancestral forms
Squid have differentiated from their ancestral molluscs such that the body plan has been condensed antero-posteriorly and extended dorso-ventrally. What before may have been the footFoot
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...
of the ancestor is modified into a complex set of tentacles and highly developed sense organs, including advanced eyes similar to those of vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s.
The ancestral shell has been lost, with only an internal gladius, or pen, remaining. The pen is a feather-shaped internal structure that supports the squid's 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...
and serves as a site for muscle attachment. It is made of a chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
-like substance.
Anatomy
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...
, which has a swimming fin along each side. These fins, unlike in other marine organisms, are not the main source of locomotion in most species.
The skin is covered in chromatophore
Chromatophore
Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, and cephalopods. They are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development...
s, which enable the squid to change color to suit its surroundings, making it practically invisible. The underside is also almost always lighter than the topside, to provide camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
from both prey and predator.
Under the body are openings to the mantle cavity, which contains the gills (ctenidia) and openings to the excretory and reproductive system
Reproductive system
The reproductive system or genital system is a system of organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes...
s. At the front of the mantle cavity lies the siphon, which the squid uses for locomotion via precise jet propulsion
Jet propulsion
Jet propulsion is motion produced by passing a jet of fluid in the opposite direction to the direction of motion. By conservation of momentum, the moving body is propelled in the opposite direction to the jet....
. In this form of locomotion, water is sucked into the mantle cavity and expelled out of the siphon in a fast, strong jet. The direction of the siphon can be changed, to suit the direction of travel.
Inside the mantle cavity, beyond the siphon, lies the visceral mass, which is covered by a thin, membranous epidermis
Squamous epithelium
In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...
. Under this are all the major internal organs.
Nervous system
The giant axonSquid giant axon
The squid giant axon is the very large axon that controls part of the water jet propulsion system in squid. It was discovered by English zoologist and neurophysiologist John Zachary Young in 1936...
, which may be up to 1 mm (0.04 inches) in diameter in some larger species, innervates
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
the mantle and controls part of the jet propulsion system.
As cephalopods, squid exhibit relatively high intelligence among invertebrates. For example, groups of Humboldt squid
Humboldt Squid
The Humboldt squid , also known as jumbo squid, jumbo flying squid, pota or diablo rojo , is a large, predatory squid found in the waters of the Humboldt Current in the Eastern Pacific Ocean. They are most commonly found at depths of , from Tierra del Fuego to California...
hunt cooperatively, using active communication. (See Cephalopod intelligence
Cephalopod intelligence
Cephalopod intelligence has an important comparative aspect in the understanding of intelligence because it relies on a nervous system fundamentally different from that of vertebrates...
.)
Reproductive system
In females the ink sacInk sac
With the exception of nocturnal and very deep water cephalopods, all coeloids which dwell in light conditions have an ink sac, which can be used to expel a cloud of dark ink to confuse predators. This sac is a muscular bag which originated as an extension of the hind gut...
is hidden from view by a pair of white nidamental gland
Nidamental gland
The nidamental gland is an internal organ found in some elasmobranchs and certain molluscs, including cephalopods and gastropods....
s, which lie anterior to the gills. There are also red-spotted accessory nidamental glands. Both organs are associated with food manufacture and shells for the eggs. Females also have a large translucent ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
, situated towards the posterior of the visceral mass.
Males do not possess these organs, but instead have a large testis in place of the ovary, and a spermatophoric gland and sac. In mature males, this sac may contain spermatophore
Spermatophore
A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...
s, which are placed inside the female's mantle during mating.
Shallow water species of 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 epipelagic/mesopelagic
Mesopelagic
The mesopelagic is that part of the pelagic zone that extends from a depth of 200 to 1000 metres below the ocean surface. It lies between the photic epipelagic above and the aphotic bathypelagic below, where there is no light at all...
zones are characterised by the presence of hectocotyli, specially modified arms used to fertilise the female's eggs. Most deep sea squid lack hectocotyli and have longer penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
es; Ancistrocheiridae and Cranchiinae
Cranchiinae
Cranchiinae is a subfamily containing four genera of glass squids.-Species:*Genus Cranchia**Cranchia scabra*Genus Drechselia ***Drechselia danae **Genus Leachia**Leachia cyclura**Leachia ellipsoptera...
are exceptions. Giant squid
Giant squid
The giant squid is a deep-ocean dwelling squid in the family Architeuthidae, represented by as many as eight species...
of the genus Architeuthis are unusual in that they possess both a large penis and modified arm tips, although it is uncertain whether the latter are used for spermatophore transfer. Penis elongation has been observed in the deep water species Onykia ingens; when erect, the penis may be as long as the mantle, head and arms combined. As such, deep water squid have the greatest known penis length relative to body size of all mobile animals, second in the entire animal kingdom only to certain sessile barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s.
Digestive system
Like all cephalopods, squid have complex digestive systems. The muscular stomachStomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
is found roughly in the midpoint of the visceral mass. From there, the bolus
Bolus (digestion)
In digestion, a bolus is a mass of food that has been chewed at the point of swallowing. Once a bolus reaches the stomach, digestion begins....
moves into the caecum for digestion. The caecum, a long, white organ, is found next to the ovary or testis. In mature squid, more priority is given to reproduction such that the stomach and caecum often shrivel up during the later life stages. Finally, food goes to the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
(or digestive gland), found at the siphon end, for absorption. Solid waste is passed out of the rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...
. Beside the rectum is the ink sac, which allows a squid to rapidly discharge black ink into the mantle cavity.
Cardiovascular system
Squid have three heartHeart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
s. Two branchial heart
Branchial heart
Branchial hearts are myogenic accessory pumps found in coleoid cephalopods that supplement the action of the main, systemic heart. Each consists of a single chamber and they are always paired, being located at the base of the gills. They pump blood through the gills via the afferent branchial veins...
s feed the gills, each surrounding the larger systemic heart that pumps blood around the body. Squid blood contains the copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
-rich protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
hemocyanin
Hemocyanin
Hemocyanins are respiratory proteins in the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule . Oxygenation causes a color change between the colorless Cu deoxygenated form and the blue Cu oxygenated form...
for transporting oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
. The faintly greenish hearts are surrounded by the renal sacs - the main excretory system. The kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s are difficult to identify and stretch from the hearts (located at the posterior side of the ink sac) to the liver. The systemic heart is made of three chambers, a lower ventricle
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
and two upper auricles.
Head
The head end bears 8 arms and 2 tentacles, each a form of muscular hydrostatMuscular hydrostat
A muscular hydrostat is a biological structure found in animals. It is used to manipulate items or to move its host about and consists mainly of muscles with no skeletal support...
containing many suckers along the edge. These tentacles do not grow back if severed. In the mature male, one basal half of the left ventral tentacle is hectocotylised
Hectocotylus
A hectocotylus is one of the arms of the male of most kinds of cephalopods that is modified in various ways to effect the fertilization of the female's eggs. It is a specialized, extended muscular hydrostat used to store spermatophores, the male gametophore...
— and ends in a copulatory pad rather than suckers. It is used for intercourse.
The mouth is equipped with a sharp horny beak mainly made of chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
and cross-linked proteins, and is used to kill and tear prey into manageable pieces. The beak is very robust, but does not contain minerals, unlike the teeth and jaws of many other organisms, including marine species.
Captured whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s often have indigestible squid beaks in their stomachs. The mouth contains the radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
(the rough tongue common to all molluscs except bivalvia
Bivalvia
Bivalvia is a taxonomic class of marine and freshwater molluscs. This class includes clams, oysters, mussels, scallops, and many other families of molluscs that have two hinged shells...
).
The eyes, on either side of the head, each contain a hard lens
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...
. The image is focused by changing the position of the lens, as in a camera
Camera
A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...
or telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
, rather than changing the shape of the lens, as in the human eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
.
Squid appear to have limited hearing.
Size
The majority are no more than 60 centimetres (23.6 in) long, although the giant squid
Giant squid
The giant squid is a deep-ocean dwelling squid in the family Architeuthidae, represented by as many as eight species...
may reach 13 metres (42.7 ft).
In 1978, sharp, curved claws on the suction cups of squid tentacles cut up the rubber coating on the hull of the USS Stein
USS Stein (FF-1065)
The third USS Stein was a Knox-class destroyer escort, later redesignated as a frigate in the United States Navy.The USS Stein was named after Tony Stein, the first Marine to receive the Medal of Honor for action in the Battle of Iwo JimaStein was laid down on 1 June 1970 at Seattle, Washington,...
. The size suggested the largest squid known at the time.
In 2003, a large specimen of an abundant but poorly understood species, Mesonychoteuthis hamiltoni (the Colossal Squid
Colossal Squid
The colossal squid , sometimes called the Antarctic or giant cranch squid, is believed to be the largest squid species in terms of mass. It is the only known member of the genus Mesonychoteuthis...
), was discovered. This species may grow to 14 metres (45.9 ft) in length, making it the largest invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
. Squid have the largest eyes in the animal kingdom. Giant squid are featured in literature and folklore with a frightening connotation. The Kraken
Kraken
Kraken are legendary sea monsters of giant proportions said to have dwelt off the coasts of Norway and Iceland.In modern German, Krake means octopus but can also refer to the legendary Kraken...
is a legendary tentacled monster possibly based on sightings of real giant squid.
In February 2007, a New Zealand fishing vessel caught a Colossal Squid
Colossal Squid
The colossal squid , sometimes called the Antarctic or giant cranch squid, is believed to be the largest squid species in terms of mass. It is the only known member of the genus Mesonychoteuthis...
weighing 495 kilograms (1,091.3 lb) and measuring around 10 metres (32.8 ft) off the coast of Antarctica. This specimen represents the largest cephalopod to ever be scientifically documented.
Classification
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
a, subclass Coleoidea
Coleoidea
Subclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the primarily soft-bodied creatures. Unlike its sister group Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal bone or shell that is used for buoyancy or support...
, order Teuthida, of which there are two major suborders, Myopsina
Myopsina
Myopsina is a suborder of squid containing two families. Some systematists raise it to the level of an order, in which case it is known as Myopsida.-External links:*...
and Oegopsina
Oegopsina
Oegopsina is a suborder of the squid order, Teuthida, in the Cephalopod Class. Some taxonomists raise it to the level of an order, in which case it is known as Oegopsida....
(including giant squid
Giant squid
The giant squid is a deep-ocean dwelling squid in the family Architeuthidae, represented by as many as eight species...
s like Architeuthis dux). Teuthida is the largest cephalopod order with around 300 species classified into 29 families.
The order Teuthida is a member of the superorder Decapodiformes
Decapodiformes
Decapodiformes is a superorder of Cephalopoda, which includes all species with ten limbs; the name derives from the Greek word meaning ten feet. The ten limbs are divided into 8 short arms and 2 long tentacles. It is presumed that an ancestral coleoid had five identical pairs of limbs, and that one...
(from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
for "ten legs"). Two other orders of decapodiform cephalopods are also called squid, although they are taxonomically
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
distinct from Teuthida and differ recognizably in their gross anatomical features. They are the bobtail squid
Bobtail squid
Bobtail squid are a group of cephalopods closely related to cuttlefish. Bobtail squid tend to have a rounder mantle than cuttlefish and have no cuttlebone. They have eight suckered arms and two tentacles and are generally quite small...
of order Sepiolida and the ram's horn squid
Ram's Horn Squid
Spirula spirula is a species of deepwater squid-like cephalopod mollusk. It is the only extant member of the genus Spirula, the family Spirulidae, and the order Spirulida...
of the monotypic order Spirulida
Spirulida
Spirulida is an order of cephalopods comprising one extant species and several extinct taxa.-Classification:*Order Spirulida**?Family Shimanskyidae**Suborder †Groenlandibelina***Family †Groenlandibelidae...
. The vampire squid
Vampire Squid
The vampire squid is a small, deep-sea cephalopod found throughout the temperate and tropical oceans of the world. Unique retractile sensory filaments justify the Vampire Squid's placement in its own order: Vampyromorphida , which shares similarities with both squid and octopuses...
, however, is more closely related to the octopuses than to any squid.
- CLASS CEPHALOPODA
- Subclass Nautiloidea: nautilus
- Subclass ColeoideaColeoideaSubclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the primarily soft-bodied creatures. Unlike its sister group Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal bone or shell that is used for buoyancy or support...
: squid, octopusOctopusThe octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
, cuttlefishCuttlefishCuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....
- Superorder OctopodiformesOctopodiformesOctopodiformes is a superorder of the subclass Coleoidea. It comprises the octopuses and the vampire squid. All members of Octopodiformes have 8 arms.-Classification:*Class Cephalopoda**Subclass Nautiloidea: nautilus**Subclass †Ammonoidea: ammonites...
- Superorder DecapodiformesDecapodiformesDecapodiformes is a superorder of Cephalopoda, which includes all species with ten limbs; the name derives from the Greek word meaning ten feet. The ten limbs are divided into 8 short arms and 2 long tentacles. It is presumed that an ancestral coleoid had five identical pairs of limbs, and that one...
- ?Order †BoletzkyidaBoletzkyidaThe Boletzkyda are perhaps the very earliest of the teuthid coleoid cephalopods, which seem to form a link between nautiloid orthocerids and more advanced coleoids. The Beletzkyda was named and described by Bandel, Reitner, and Sturmer in 1983 from specimens found the Lower Devonian black slate...
- Order SpirulidaSpirulidaSpirulida is an order of cephalopods comprising one extant species and several extinct taxa.-Classification:*Order Spirulida**?Family Shimanskyidae**Suborder †Groenlandibelina***Family †Groenlandibelidae...
: Ram's Horn Squid - Order Sepiida: cuttlefish
- Order Sepiolida: bobtail squid
- Order Teuthida: squid
- Family †PlesioteuthididaePlesioteuthididaePlesioteuthididae is an extinct family of squid.-External links:**...
(incertae sedisIncertae sedis, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
) - Suborder MyopsinaMyopsinaMyopsina is a suborder of squid containing two families. Some systematists raise it to the level of an order, in which case it is known as Myopsida.-External links:*...
- Family Australiteuthidae
- Family LoliginidaeLoliginidaeLoliginidae, commonly known as pencil squids, is an aquatic family of the order Teuthida .-Species:The following classification follows Vecchione et al. and the Tree of Life Web Project .*Genus Afrololigo...
: inshore, calamari, and grass squid
- Suborder OegopsinaOegopsinaOegopsina is a suborder of the squid order, Teuthida, in the Cephalopod Class. Some taxonomists raise it to the level of an order, in which case it is known as Oegopsida....
- Family AncistrocheiridaeSharpear Enope SquidThe Sharpear Enope Squid is the only species in the genus Ancistrocheirus and family Ancistrocheiridae. With a mantle length of 25 cm, this moderately sized squid may be found throughout the tropical and subtropical oceans...
: Sharpear Enope Squid - Family Architeuthidae: giant squid
- Family BathyteuthidaeBathyteuthisBathyteuthis is the singular genus of squid in the family Bathyteuthidae, encompassing three species. None obtain a mantle length greater than 80 mm....
- Family BatoteuthidaeBush-club SquidBush-club Squid is the single rare species in genus Batoteuthis, which is the only genus in family Batoteuthidae. The squid is found in Antarctic waters, and reaches a mantle length of at least 350 mm...
: Bush-club Squid - Family BrachioteuthidaeBrachioteuthidaeBrachioteuthidae is a family of squid. It contains two genera and around six species.-Species:*Genus Brachioteuthis**Brachioteuthis beanii**Brachioteuthis behnii**Brachioteuthis bowmani ***Brachioteuthis picta, Ornate Arm Squid...
- Family ChiroteuthidaeChiroteuthidaeChiroteuthids are deep-sea squid of the family Chiroteuthidae. They are generally small to medium in size, rather soft and gelatinous, and slow moving. They are found in most temperate and tropical oceans, but are known primarily from the North Atlantic, North Pacific, and Indo-Pacific...
- Family ChtenopterygidaeChtenopteryxChtenopteryx is a genus of small, muscular, midwater squid in the monotypic family Chtenopterygidae. Four species are presently recognized in the genus, but more are believed to exist....
: comb-finned squid - Family CranchiidaeGlass squidThe family Cranchiidae comprises the approximately 60 species of glass squid, also known as cranchiid or cranch squid. Cranchiid squid occur in surface and midwater depths of open oceans around the world. They range in mantle length from to over , in the case of the Colossal Squid. The common...
: glass squid - Family CycloteuthidaeCycloteuthidaeCycloteuthidae is a family in the order Teuthida, comprising two genera. While physically dissimilar, molecular evidence supports the relatedness of the genera. The family is found primarily in mesopelagic tropical to subtropical waters...
- Family EnoploteuthidaeEnoploteuthidaeEnoploteuthidea is a family of squid comprising approximately 40 species in 4 genera. Most species have a mantle length ranging from 3-13 cm. Hooks are present on all arms and tentacles...
- Family GonatidaeGonatidaeThe 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...
: armhook squid - Family HistioteuthidaeHistioteuthisHistioteuthis is a genus of squid and the only member of the Histioteuthidae family. It goes by the English name cock-eyed squid, because in all species the right eye is normal-sized, round, blue and sunken; whereas the left eye is at least twice the diameter of the right eye, tubular,...
: jewel squid - Family JoubiniteuthidaeJoubin's SquidJoubin's Squid is a rare, small squid found in both the Atlantic Ocean, Pacific Ocean and in rare cases, the Indian Ocean. The species is named after Louis Joubin, a French zoologist. It is known to reach a mantle length of 9 cm....
: Joubin's Squid - Family LepidoteuthidaeGrimaldi Scaled SquidThe Grimaldi Scaled Squid is a large squid growing to 1 m in mantle length. It is named after the Grimaldi family, reigning house of Monaco. Prince Albert I of Monaco was an amateur teuthologist who pioneered the study of deep sea squids by collecting the 'precious regurgitations' of sperm...
: Grimaldi Scaled Squid - Family LycoteuthidaeLycoteuthidaeLycoteuthidae is a family of squid comprising four known genera in two subfamilies. They are characterised by a lack of hooks and by photophores present on the viscera, eyeballs and tentacles.-Species:Subfamily Lampadioteuthinae...
- Family MagnapinnidaeBigfin squidThe bigfin squids are a group of rarely seen cephalopods with a distinctive morphology. They are placed in the genus Magnapinna and family Magnapinnidae...
: bigfin squid - Family Mastigoteuthidae: whip-lash squid
- Family NeoteuthidaeNeoteuthidaeNeoteuthidae is a family of squid comprising four monotypic genera.-Species:* Alluroteuthis** Alluroteuthis antarcticus, Antarctic Neosquid* Narrowteuthis** Narrowteuthis nesisi* Neoteuthis** Neoteuthis thielei* Nototeuthis...
- Family OctopoteuthidaeOctopoteuthidaeOctopoteuthidae is a family of squid comprising two genera. The family is characterised by tentacles which cease to grow after the paralarval stage; and the use of a penis, instead of a hectocotylus.-Species:*Genus Octopoteuthis**Octopoteuthis danae...
- Family OmmastrephidaeOmmastrephidaeOmmastrephidae is a family of squid. It contains 3 subfamilies, 11 genera, and over 20 species.-External links:***...
: flying squid - Family Onychoteuthidae: hooked squid
- Family PholidoteuthidaePholidoteuthisPholidoteuthis is a genus of squid in the monotypic family Pholidoteuthidae, comprising at least two species. The defunct genus Tetronychoteuthis was previously incorporated into Pholidoteuthidae based upon a singular taxon known as Tetronychoteuthis massyae. Following the discovery of...
- Family PromachoteuthidaePromachoteuthisPromachoteuthis is a genus of small, weakly muscled squid found at bathypelagic depths. Three species have been formally described, while another two await description.-External links:**...
- Family PsychroteuthidaeGlacial SquidThe Glacial Squid is the only known species in the monotypic genus Psychroteuthis, in the family Psychroteuthidae. While only one species has been confirmed, it is possible that two undescribed species also exist. The species occurs in coastal waters near Antarctica and South America. It grows to...
: Glacial Squid - Family PyroteuthidaePyroteuthidaeFire squid are species belonging to the family Pyroteuthidae. The family comprises two genera. Species are diurnally mesopelagic, however migrate into surface waters during the night. The family is characterised by the tentacles, which have a permanent constriction and bend near the base; and...
: fire squid - Family ThysanoteuthidaeThysanoteuthisThysanoteuthis is a genus of large squid comprising one well known species, the Diamond Squid, and two dubious taxa.-Species:*? Thysanoteuthis danae **Thysanoteuthis nuchalis **Thysanoteuthis rhombus, Diamond Squid or Diamondback Squid...
: rhomboid squid - Family WalvisteuthidaeWalvisteuthisWalvisteuthis is a genus of squid consisting of a single species, Walvisteuthis virilis. It is found in the southern Atlantic Ocean...
- Parateuthis tunicata (incertae sedisIncertae sedis, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
)
- Family Ancistrocheiridae
- Family †Plesioteuthididae
- ?Order †Boletzkyida
- Superorder Octopodiformes
Commercial fishing
According to the FAOFão
Fão is a town in Esposende Municipality in Portugal....
, the cephalopod catch for 2002 was 3173272 tonnes (6,995,867,236.5 lb). Of this, 2,189,206 tonnes, or 75.8 percent, was squid. The following table lists the squid species fishery catches which exceeded 10000 tonnes (22,046,226.2 lb) in 2002.
| World squid catch in 2002 | ||||
| Species | Family | Common name | Catch tonnes |
Percent |
|---|---|---|---|---|
| Loligo gahi | Loliginidae Loliginidae Loliginidae, commonly known as pencil squids, is an aquatic family of the order Teuthida .-Species:The following classification follows Vecchione et al. and the Tree of Life Web Project .*Genus Afrololigo... |
Patagonian squid | 24,976 | 1.1 |
| Loligo pealei | Loliginidae Loliginidae Loliginidae, commonly known as pencil squids, is an aquatic family of the order Teuthida .-Species:The following classification follows Vecchione et al. and the Tree of Life Web Project .*Genus Afrololigo... |
Longfin squid | 16,684 | 0.8 |
| Common squid nei | Loliginidae Loliginidae Loliginidae, commonly known as pencil squids, is an aquatic family of the order Teuthida .-Species:The following classification follows Vecchione et al. and the Tree of Life Web Project .*Genus Afrololigo... |
225,958 | 10.3 | |
| Ommastrephes bartramii | Ommastrephidae Ommastrephidae Ommastrephidae is a family of squid. It contains 3 subfamilies, 11 genera, and over 20 species.-External links:***... |
Neon flying squid Neon flying squid Ommastrephes bartramii , is a species of large flying squids in the family Ommastrephidae... |
22,483 | 1.0 |
| Illex argentinus | Ommastrephidae Ommastrephidae Ommastrephidae is a family of squid. It contains 3 subfamilies, 11 genera, and over 20 species.-External links:***... |
Argentine shortfin squid Argentine Shortfin Squid Illex argentinus, commonly known as the Argentine Shortfin Squid, is a species of squid in the family Ommastrephidae.It is one of the most commercially fished species of squid, with 511,087 tons taken in 2002, or 23.3% of the entire squid harvest.... |
511,087 | 23.3 |
| Dosidicus gigas | Ommastrephidae Ommastrephidae Ommastrephidae is a family of squid. It contains 3 subfamilies, 11 genera, and over 20 species.-External links:***... |
Jumbo flying squid | 406,356 | 18.6 |
| Todarodes pacificus | Ommastrephidae Ommastrephidae Ommastrephidae is a family of squid. It contains 3 subfamilies, 11 genera, and over 20 species.-External links:***... |
Japanese flying squid Japanese Flying Squid The Japanese Flying Squid or Japanese Common Squid, Todarodes pacificus, is a squid of the family Ommastrephidae. This animal lives in the northern Pacific Ocean, in the area surrounding Japan, up the full coast of China up to Russia, then spreading across the Bering Straight over towards the lower... |
504,438 | 23.0 |
| Nototoda russloani | Ommastrephidae Ommastrephidae Ommastrephidae is a family of squid. It contains 3 subfamilies, 11 genera, and over 20 species.-External links:***... |
Wellington Flying Squid | 62,234 | 2.8 |
| Squid nei | Various | 414,990 | 18.6 | |
| Total squid | 2,189,206 | 100.0 | ||
As food
Chinese cuisine
Chinese cuisine is any of several styles originating in the regions of China, some of which have become highly popular in other parts of the world – from Asia to the Americas, Australia, Western Europe and Southern Africa...
, Greek, Turkish
Turkish cuisine
Turkish cuisine is largely the heritage of Ottoman cuisine, which can be described as a fusion and refinement of Central Asian, Middle Eastern and Balkan cuisines. Turkish cuisine has in turn influenced those and other neighbouring cuisines, including that of western Europe...
, Japanese
Japanese cuisine
Japanese cuisine has developed over the centuries as a result of many political and social changes throughout Japan. The cuisine eventually changed with the advent of the Medieval age which ushered in a shedding of elitism with the age of shogun rule...
, Portuguese
Portuguese cuisine
Portuguese cuisine is characterised by rich, filling and full-flavored dishes and is closely related to Mediterranean cuisine. The influence of Portugal's former colonial possessions is also notable, especially in the wide variety of spices used. These spices include piri piri and black pepper, as...
, Italian
Italian cuisine
Italian cuisine has developed through centuries of social and political changes, with roots as far back as the 4th century BCE. Italian cuisine in itself takes heavy influences, including Etruscan, ancient Greek, ancient Roman, Byzantine, Jewish and Arab cuisines...
, Spanish
Spanish cuisine
Spanish cuisine consists of a variety of dishes, which stem from differences in geography, culture and climate. It is heavily influenced by seafood available from the waters that surround the country, and reflects the country's deep maritime roots...
, Korean, Indian
Indian cuisine
Indian cuisine consists of thousands of regional cuisines which date back thousands of years. The dishes of India are characterised by the extensive use of various Indian spices, herbs, vegetables and fruit. Indian cuisine is also known for the widespread practice of vegetarianism in Indian society...
, Vietnamese, and Filipino.
In English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
-speaking countries, squid as food is often marketed using the Italian word calamari. Squid are found abundantly in certain areas, and provide large catches for fisheries
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
. The body can be stuffed whole, cut into flat pieces or sliced into rings. The arms, tentacles and ink are also edible; in fact, the only parts that are not eaten are the beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
and gladius
Gladius
Gladius was the Latin word for sword, and is used to represent the primary sword of Ancient Roman soldiers. Early ancient Roman swords were similar to those used by the Greeks. From the 3rd century BC, the Romans adopted swords similar to those used by the Celtiberians and others during the early...
(pen). Squid is a good food source for zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
and high in the recommended daily intake of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, selenium
Selenium
Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...
, vitamin B12
Vitamin B12
Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
, and riboflavin
Riboflavin
Riboflavin, also known as vitamin B2 or additive E101, is an easily absorbed micronutrient with a key role in maintaining health in humans and animals. It is the central component of the cofactors FAD and FMN, and is therefore required by all flavoproteins. As such, vitamin B2 is required for a...
.