SQUID
This article is about the sea animal. For other uses of "squid", see Squid (disambiguation).
Myopsina
Oegopsina
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The
squid is a marine
mollusk of the class
Cephalopoda, subclass
Coleoidea, order
Teuthida, of which there are two major suborders,
Myopsina and
Oegopsina (including the
giant squids like
Architeuthis dux). Teuthida is the largest of the cephalopod orders, edging out the octopuses (order
Octopoda) for total number of species, with 298 classified into 28 families.
The order Teuthida is a member of the superorder Decapodiformes (literally "ten legged"). Two other orders of decapodiform cephaopods are also called squid, although they are
taxonomically disctinct from Teuthida and differ recognizably in their gross anatomical features. They are the
bobtail squids of order
Sepiolida, and the
Ram's Horn Squid of the single species order
Spirulida. The
Vampire Squid, however, is more closely related to the octopuses than to any other squid.
Like all cephalopods, squids are distinguished by having a distinct head, bilateral symmetry and
tentacles with suckers; squid, like
cuttlefish, have eight arms and two tentacles arranged in pairs. They also have
chromatophores imbedded in their
skin and the ability to expel
ink if threatened. Being coleoids means that their bony structure is internalized (in the
octopus it is nonexistent); in squid there is a single flat
bone plate buried within the soft tissue structure. They have a specialized foot called the siphon, or hyponome, that enables them to move by expelling water under pressure. Squid are the most skilled of the coleoids at this form of motion. The mouth of the squid is beak-like and made of
chitin, and contains the
radula (the rough tongue common to all molluscs).
Squid have two
gills and an extensive closed
circulatory system with one major and two subsidiary
hearts.
They are exclusively
carnivorous, feeding on fish and other invertebrates. Squid usually have two elongated tentacles especially for the capture of food.
The majority of squid are no more than 60 cm in length, but the
giant squid is reportedly up to 20m in length, which made it the largest invertebrate in the world, and it has the largest eyes of all. Recently, however, an even larger specimen of a poorly understood species,
Mesonychoteuthis hamiltoni (the
Colossal Squid) has been discovered.
Individual species of squid are found abundantly in certain areas and provide large catches for
fisheries.
Squid is a popular food in many parts of the world, and finds its way into cuisines as widely separated as the
Japanese and the
Italian. In American fish markets and restaurants, it is usually known by the Greek plural
calamari.
Classification
