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The colossal squid (Mesonychoteuthis hamiltoni) is the heaviest known living invertebrate and one of the largest cephalopods ever discovered. Colossal squid belong to the glass squid family, though the majority of other species in this family are small to medium in size with much less muscle density than the colossal squid. Adult colossal squid can reach a mantle length of about 8 ft (2.5 meters) and a total length of about 33 ft (10 meters). The largest confirmed specimen, a female captured near New Zealand in 2007, weighed approximately 1091 lbs (495 kilograms). Colossal squid are much more
robust than even the longest cephalopod, the giant squid (Architeuthis dux). Colossal squid inhabit the cold waters of the Southern Ocean. They have a circumpolar distribution around Antarctica. Adults live in the deep ocean, near the seafloor. They are quite abundant, but rarely seen. Their mantle is long, with two fins at the top that taper to a point. They have huge, protruding eyes that possess light-producing organs called photophores. Their eyes currently hold the record for the largest eyes in the animal kingdom. They have eight arms and two long feeding tentacles. The
feeding tentacles are kept hidden when not in use. They have swiveling hooks on their tentacle clubs. Several pairs of suckers toward the middle of each of their eight arms also develop into large, swiveling, claw-like hooks as a colossal squid matures. As juveniles, they are quite transparent, but they lose their see-through appearance as they grow. Their life cycle is poorly understood, but it is believed that they undergo major changes in habitat as they grow. Very young paralarvae can occur from relatively close to the surface to 1600 ft (500 meters) deep. Juveniles and subadults
gradually move into deeper waters, from 1600 ft (500 m) to more than 6500 ft (2,000 m). Adults are concentrated even deeper, and may occur at depths approaching 13,100 ft (4,000 m). Colossal squid are powerful predators and they occupy a position near the top of the Southern Ocean food web. Their diet includes organisms such as lanternfish (myctophids), Patagonian toothfish, sleeper sharks, and other squid. Cannibalism may also occur. Rather than relying on high-speed pursuit, it is believed that colossal squid are primarily ambush predators, using their
arms and specialized tentacles to seize prey. Colossal squid are preyed on by numerous Southern Ocean animals such as seabirds, fish, seals, and whales. Sperm whales are particularly important predators of large colossal squid and appear to be the principal predators capable of regularly consuming healthy adults. Reproduction of this species is poorly understood. Spawning is thought to occur during the Antarctic summer, with females potentially making vertical migrations from deep water toward shallower regions to reproduce. For more marine facts, click the SUBSCRIBE button!
