The colossal squid (Mesonychoteuthis hamiltoni) 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).

This species shares anatomy similar to other members of its family although it is the only member of Cranchiidae to display hooks on its arms and tentacles. It is known to inhabit the circumantarctic Southern Ocean. Although little is known about the behavior, it is known to use bioluminescence to attract prey. Additionally, it is presumed to be an ambush predator, and is a major prey of the sperm whale.

The first specimens were discovered and described in 1925. In 1981, an adult specimen was discovered, and in 2003 a second specimen was collected. Captured in 2007, the largest live colossal squid weighed 495 kilograms (1,091 lb), and is now on display with a second specimen at the Museum of New Zealand Te Papa Tongarewa.

 

Note:   The above text is excerpted from the Wikipedia article Colossal squid, which has been released under the GNU Free Documentation License.