Colossal squid

The colossal squid (Mesonychoteuthis hamiltoni) is a species of very large squid belonging to the family Cranchiidae, that of the cockatoo squids, or glass squids. It is sometimes called the Antarctic cranch squid or giant squid (not to be confused with the giant squid in genus Architeuthis) and is believed to be the largest squid species in terms of mass. It is the only recognized member of the genus Mesonychoteuthis. The species is confirmed to have a mass of at least 495 kilograms (1,091 lb), although some specimens, known only from beaks found in sperm whale stomachs, may have weighed as much as 600–700 kilograms (1,300–1,500 lb), making the squid the largest extant invertebrate. The maximum total length is ~4.2 metres (14 ft). Larger estimates exist; however, these include the feeding tentacles measured on dead specimens. In life the squid's tentacles are hidden, only released when capturing prey. If tentacles are considered, lengths of 10 metres (33 ft) and 14 metres (46 ft) exist, but the former estimate is more likely. The colossal squid has the largest eyes of any known creature ever to exist, with an estimated diameter of 27–30 cm (11–12 in) to 40 cm (16 in) for the largest collected specimen. The species has anatomy similar to that of other members of its family, although it is the only member of Cranchiidae to display hooks on its arms, suckers, and tentacles. It is known to inhabit the circumantarctic Southern Ocean. It is presumed to be an ambush predator, with a diet including various fish, and is likely a key prey item of the sperm whale.