The colossal squid, Mesonychoteuthis hamiltoni, is a creature of myth and mystery, dwelling in the cold, dark depths of the Southern Ocean. It is the largest invertebrate on Earth and the world’s largest mollusc, surpassing even the giant squid in mass. Although it shares a few similarities with other squid species, the colossal squid is unique and remains largely an enigma to science.
These deep-sea giants can reach impressive sizes. While the longest recorded length is 4.2 meters (13.8 feet), with a weight of 470 kg (1036 pounds), some scientists estimate they may grow up to 10-14 meters (33-46 feet) long and weigh as much as 700 kg (1,500 lb). Adult females are typically larger than males. The colossal squid has the largest eyes in the animal kingdom, with diameters ranging from 27-40 cm (11-16 inches). These huge eyes are thought to be an adaptation for spotting predators like sperm whales. Adding to their fearsome appearance, the colossal squid’s arms and tentacles are equipped with rotating hooks, used for capturing prey.
Colossal squid are found primarily in the Southern Ocean surrounding Antarctica, with sightings as far north as New Zealand. They inhabit the mesopelagic to bathypelagic zones of the open ocean. Young squid are found in shallower waters, but as they mature they descend to greater depths.
Little is known about the colossal squid’s behaviour, but it is believed to be an ambush predator, feeding on fish, including Patagonian toothfish, as well as other squids and chaetognatha. They have a slow metabolic rate and are thought to drift passively, waiting for prey to come close. Sperm whales are their main predator, with evidence of colossal squid beaks found in their stomachs, making up 77% of the whale’s biomass consumed. Other predators include southern sleeper sharks, pilot whales, elephant seals, and albatrosses.
The colossal squid was first discovered in 1925, with initial specimens consisting of arm fragments found in the stomach of a sperm whale. Since then, only a few complete specimens have been recorded. The largest specimen, a female, was captured in 2007 in the Ross Sea and is now on display at the Museum of New Zealand Te Papa Tongarewa. It weighed 495 kg and had a total length of 4.2 meters. This specimen required special handling to preserve it for display, including a slow thawing process and submersion in a special liquid.
Despite their large size and fearsome reputation, colossal squid are classified as a species of least concern by the IUCN. They are not targeted by fisheries, and their deep-sea habitat means they rarely interact with humans. Scientists continue to study these fascinating creatures in the hopes of better understanding their biology and ecology.
Expeditions are ongoing to film live colossal squid in their natural habitat to better understand these animals. The data collected is critical to assessing their population trends and the health of the Southern Ocean’s ecosystem.
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