A squid is a mollusc 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 these criteria. Like all other cephalopods, squid have a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen, made of chitin.
The giant squid is a species of deep-ocean dwelling squid in the family Architeuthidae. It can grow to a tremendous size, offering an example of abyssal gigantism: recent estimates put the maximum size at around 12–13 m (39–43 ft) for females and 10 m (33 ft) for males, from the posterior fins to the tip of the two long tentacles. The mantle of the giant squid is about 2 m long, and the length of the squid excluding its tentacles rarely exceeds 5 m (16 ft). Claims of specimens measuring 20 m (66 ft) or more have not been scientifically documented.
Spirula spirula is a species of deep-water squid-like cephalopod mollusk. It is the only extant member of the genus Spirula, the family Spirulidae, and the order Spirulida. Because of the shape of its internal shell, it is commonly known as the ram's horn squid or the little post horn squid. Because the live animal has a light-emitting organ, it is also sometimes known as the tail-light squid.
The Mastigoteuthidae, also known as whip-lash squid, are a family of small deep-sea squid. Approximately 20 known species in six genera are represented, with members found in both the mesopelagic and bathypelagic zone of most oceans. Originally described by Verill in 1881, it was later lowered by Chun (1920) to a subfamily (Mastigoteuthinae) of the Chiroteuthidae. However, Roper et al. (1969) raised it back to the family level, and this has not been changed since. The taxonomy of this family is extremely unstable, and there have been at times one genus, two genera and four subgenera(Salcedo-Vargas & Okutani, 1994), two genera and several 'groups', five genera and one species with an uncertain placement, or six genera.
Bigfin squids are a group of rarely seen cephalopods with a distinctive morphology. They are placed in the genus Magnapinna and family Magnapinnidae. Although the family was described only from larval, paralarval, and juvenile specimens, numerous video observations of larger squid with similar morphology are assumed to be adult specimens of the same family.
Taningia danae, the Dana octopus squid, is a species of squid in the family Octopoteuthidae. It is one of the largest known squid species, reaching a mantle length of 1.7 m (5.6 ft) and total length of 2.3 m (7.5 ft). The largest known specimen, a mature female, weighed 161.4 kg (356 lb).
Cephalopods, which include squids and octopuses, vary enormously in size. The smallest are only about 1 centimetre (0.39 in) long and weigh less than 1 gram (0.035 oz) at maturity, while the largest—the giant and colossal squids—can exceed 10 metres (33 ft) in length and weigh close to half a tonne (1,100 lb), making them the largest living invertebrates. Living species range in mass more than three-billion-fold, or across nine orders of magnitude, from the lightest hatchlings to the heaviest adults. Certain cephalopod species are also noted for having individual body parts of exceptional size. The giant and colossal squids, for example, have the largest known eyes among living animals.
Magnapinna atlantica, previously known as "Magnapinna sp. A", is a species of bigfin squid known from only two specimens collected in the northern Atlantic Ocean. It is characterised by several unique morphological features: the tentacle bases are narrower than adjacent arm bases, the proximal tentacle lacks suckers but possesses glandular structures, and the animal's pigment is contained mostly in functional chromatophores.
Magnapinna pacifica is a species of bigfin squid known only from three immature specimens; two caught at a depth of less than 300 m and one from a fish stomach. M. pacifica is the type species of the genus Magnapinna. It is characterised primarily by its proximal tentacles, which are wider than adjacent arms and bear numerous suckers.
Magnapinna talismani is a species of bigfin squid known only from a single damaged specimen. It is characterised by small white nodules present on the ventral surface of its fins.
Magnoteuthis is a genus of whip-lash squid containing at least three species. Some teuthologists consider Idioteuthis or Mastigoteuthis synonymous with this taxon, but it is genetically and morphologically distinct.
Asperoteuthis acanthoderma is a large species of squid belonging to the family Chiroteuthidae. It is characterised by the tiny, pointed tubercules present on its skin and a Y-shaped groove in the funnel locking apparatus.
Promachoteuthis sulcus is a species of promachoteuthid squid. It is distinguished from related taxa on the basis of several morphological features: Nuchal fusion between the head and mantle, much larger size of arm-suckers compared to club-suckers, greater width of tentacle-base than arm-base, a recessed club-base, and the presence of an aboral tentacle-groove.
All cephalopods possess flexible limbs extending from their heads and surrounding their beaks. These appendages, which function as muscular hydrostats, have been variously termed arms, legs or tentacles.
The colossal squid is part of the family Cranchiidae. It is sometimes called the Antarctic squid or giant cranch squid and is believed to be the largest squid species in terms of mass. It is the only recognized member of the genus Mesonychoteuthis and is known from only a small number of specimens. The species is confirmed to reach a mass of at least 495 kilograms (1,091 lb), though the largest specimens—known only from beaks found in sperm whale stomachs—may perhaps weigh as much as 600–700 kilograms (1,300–1,500 lb), making it the largest known invertebrate. Maximum total length has been estimated at 9–10 metres (30–33 ft). The colossal squid has the largest eyes of any known creature ever to exist, with an estimated diameter of 27 cm (11 in).
Illex coindetii, commonly known as the southern shortfin squid or broadtail shortfin squid, is a species of neritic squids in the family Ommastrephidae. They are found in the Mediterranean Sea and on both sides of the north Atlantic Ocean.
Teuthowenia megalops, sometimes known as the Atlantic cranch squid, is a species of glass squid from the subarctic and temperate waters of the northern Atlantic Ocean. They are moderately sized squid with a maximum mantle length of 40 cm (16 in). Their very large eyes are the source for the specific name megalops. Like other members of the genus Teuthowenia, they are easily recognizable by the presence of three bioluminescent organs (photophores) on their eyeballs.
Cephalopods exhibit various dermal structures on their mantles and other parts. These may take the form of conspicuous warts, cushions, papillae or scales, though in many species they are microscopic tubercles. The most elaborate forms are found among the oceanic squid of the order Teuthida.
Mastigotragus is a genus of whip-lash squid containing a single species, Mastigotragus pyrodes. This species was originally placed within Mastigoteuthis, but has been subsequently separated from other species in that genus due to multiple morphological characters. This genus is characterized by a lack of antitragus in the funnel-locking cartilage, larger sucker rings on the tentacles, a particular photophore morphology, and relatively large eyelid photophore. This genus is Latin for 'whip-lash goat'.
Richard E. Young is a teuthologist. He is an Emeritus Professor of Oceanography at the University of Hawaii's School of Ocean and Earth Science and Technology.
