Colossal Squids: Characteristics, Feeding and Size

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Colossal Squid

In February 2007, a gigantic squid was caught in the Ross Sea, Antarctica that was eight meters long and weighed 450 kilograms, making it the largest squid ever found in terms of mass, 150 kilograms larger than the previous largest record. The creature was a colossal squid not a giant squid. [Source: Reuters]

The colossal squid was so big that if cut up it would produce rings the size of tractor tires. The squid had hundreds of hooks on its arms as well a large and powerful beak capable of easily snapping the backbone of a fish up to two meters long, Steve O’shea, a scientist at Auckland University of Technology told Reuters. The captain of the long-line fishing vessel that caught the squid told Newsweek it took his 25-man crew two hours to land the creature, which surfaced barely alive, eating a hooked Antarctic toothfish that was being pulled in. “Being alongside a creature that big is just awesome,” he said. The squid was male. After it was caught it was frozen. Scientists carefully checked it out after thawing it out a year later. It was later put on display at New Zealand’s national museum in Wellington.

The colossal squid (Mesonychoteuthis hamiltoni) is the heaviest living invertebrate species. Sometimes called the Antarctic squid or giant cranch squid and and known only from a small number of specimens, it is the largest squid species in terms of mass and the only recognized member of the genus Mesonychoteuthis. The largest confirmed specimen weighed least 495 kilograms (1,091 pounds), 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. Colossal squids are believed to have a longer mantle than giant squids. The colossal squid also has the largest eyes documented in the animal kingdom: 40 centimeters. Some of the giant squid reports may have actually been of colossal squids. [Source: Wikipedia]

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase ; Encyclopedia of Life ; Smithsonian Oceans Portal

Colossal Squid Habitat Characteristics

The range of the colossal squid extends thousands of kilometers north of Antarctica to southern South America, southern South Africa, and the southern tip of New Zealand, making it primarily an inhabitant of the entire circumantarctic Southern Ocean. Its range coincides with the Antarctic Circumpolar Current. [Source: Wikipedia, Animal Diversity Web (ADW)]

Colossal squid have been sighted near Cooperation Sea and less near Ross Sea. This also coincides with the presence of Antarctic toothfish, a predator, food and competitor of colossal squid. . The region between the Weddell Sea and the western Kerguelen archipelago has been deemed a “hotspot” based on characteristics of the habitat.

The colossal squid's vertical distribution appears to correlate directly with age. Young squid are found between 0–500 meters (0–1,640 feet), adolescent squid are found 500–2,000 meters (1,600–6,600 feet). Younger squid are concentrated closer to the surface, perhaps because there is more food for them resulting from increases phytoplankton biomass. Adult squid are found primarily within the mesopelagic zone (200 to 1,000 meters, 650 and 3,300 feet) and bathypelagic zone (1000 to 3000 meters, 3300 to 9800 feet) of the open ocean. Because adult beaks have been found in the stomachs of sperm whales, adults may reach depths of at least 2200 meters

Colossal Squid Characteristics

pulling up the colossal squid in February 2007

Colossal squid belong to the Cranchiidae family of squid, which comprises approximately 60 species of glass squid, also known as cockatoo squid, cranchiid, cranch squid, or bathyscaphoid squid. Cranchiid squid generally occur in surface and midwater depths of open oceans around the world. They range in mantle length from 10 centimeters (3.9 inches) to over three meters (9.8 feet) in the case of the colossal squid. Giant squids belong to the Architeuthidae squid family. [Source: Wikipedia]

Colossal squid have features in common with all squids, including a mantle, one pair of gills, eight arms and two tentacles, a head, and two fins. Among the morphological and anatomical characteristics that differentiate colossal squid from other squids in the family are its hooks. The colossal squid is the only squid in its family with hooks, either swivelling or three-pointed, equipped on its arms and tentacles. There are squids in other families that also have hooks, but no other squid in the family Cranchiidae.

The colossal squid exhibits abyssal gigantism. It is unclear what the maximum weight for colossal squids is. Colossal squid are essentially deaf to high frequencies (like whale sonar), and presumably rely largely on visual detection to avoid predation.

Colossal Squid Eyes and Vision

The colossal squid also has the largest eyes documented in the animal kingdom, with an estimated diameter of 30–40 centimeters (12–16 inches). For pelagic organisms of similar weight to the colossal squid, such as the swordfish, the average eye diameter required for visual detection is 10 centimeters, but colossal squid's can be almost three times that size. Colossal squid eyes glow in the dark via long rectangularly shaped light-producing photophores located next to the lens on the front of both eyeballs. Symbiotic bacteria reside within these photophores and luminesce through chemical reaction. [Source: Wikipedia]

Advantages provided by colossal squid’s large eyes include reduced diffraction blurring and greater contrast distinction. The colossal squid's increased pupil size has been mathematically proven to overcome visual complications of the pelagic zone such as the combination of downwelling daylight, bioluminescence, and light scattering with increasing distance — especially by monitoring larger volumes of water at once and by detecting long-range changes in plankton bioluminescence via the physical disruption of large moving objects such as sperm whales.

It has been presumed that the colossal squid’s large eyes must be extremely beneficial to the squid to justify the large energetic expenses to grow, move, camouflage, and maintain them. It has been hypothesized that the colossal squid's eyes may detect predator movement beyond 120 meters, which is the upper limit of the sperm whale's sonar range.

Colossal Squid Feeding, Prey and Metabolism

Colossal squid tentacle club

Colossal squids appear to not move around so much and thus don’t need so much food. They feed on chaetognatha (marine worms), smaller squid and large fish including the Patagonian toothfish, It has been estimated that one five-kilogram toothfish may provide enough energy and nutrients for a 500-kilogram squid to survive for up to 200 days. Colossal squids are thought to be ambush predators that depends on its hooks to catch prey. Because of its size and low energy intake, it most likely does not expend energy actively chasing its prey. They may use bioluminescence to attract or confuse prey.[Source: Dan Ravaioli and Tracy Youngster, Animal Diversity Web (ADW)]

A study by Remeslo, Yakushev and Laptikhovsky revealed that Antarctic toothfish make up a significant part of the colossal squid's diet. Of 8,000 toothfish brought aboard trawlers between 2011 and 2014, seventy-one showed clear signs of attack by colossal squid. A study in Prydz Bay region of Antarctica found squid remains in a female colossal squid's stomach, suggesting the possibility of cannibalism within this species.

Colossal squids thought to have a slow paced life because of their large size and low prey requirements. Their very slow metabolic rate means even a 500-kilogram squid need only around 30 grams (1 oz) of prey per day. It is believed they use their large eyes primarily for prey-detection rather than active hunting. As the squid grows older it moves into deeper and darker waters, possibly to reduce the possibility of it being detected, and also to reduce predation pressure.

Colossal Squids, Predator and Sperm Whales

Many sperm whales have scars on their backs, believed to be caused by the hooks of colossal squid. Colossal squid are a major prey item for sperm whales in the Antarctic; 14 percent of the squid beaks found in the stomachs of these sperm whales are those of the colossal squid, which indicates that colossal squid make up 77 percent of the biomass consumed by these whales. [Source: Wikipedia]

Many other animals also feed on colossal squid, including the beaked whales, such as southern bottlenose whales, Cuvier's and Baird's beaked whales. These whales resemble oversized dolphins and have a pronounced underbite on their snout (or "beak"). They are among the deepest-diving cetaceans ever recorded, besides the sperm whale. They dive to the deep depths occupied by colossal squid,

Other possible squid predators include pilot whales, larger southern elephant seals, killer whales, Patagonian toothfish, southern sleeper sharks, Antarctic toothfish, and albatrosses such as the wandering and sooty albatrosses. However, beaks from mature adults have only been recovered from large predators such as whales and southern sleeper sharks. Most of the other predators mentioned above primarily eat juveniles or young adults.

Colossal Squid Reproduction

Little is known about the reproductive behavior of colassal squids. Many squids have precopulatory rituals, and males seize females with their tentacles prior to mating. Perhaps this is true with colassal squid. Fertilization is likely internal. [Source: Dan Ravaioli and Tracy Youngster, Animal Diversity Web (ADW)]

Dissection of a mature male adult, seems to show that it had no hectocotylus (arms of male cephalopods specialized to store and transfer spermatophores to the female). which are found in most squids is found at the end of one of the male’s tentacles. Instead, it is speculated that colossal may have a penis or penises.

Many species of squid develop sex-specific organs as they age and develop. Adult female colossal squid has been discovered in much shallower waters which likely implies that they spawn in shallower waters than their normal depth. Colossal squid can release as many as 4.2 million eggs, an unusually high number compared to other cold water squids. Colossal squid eggs range in size from as large as 3.2x2.1 millimeters to as small as 1.4x0.5 millimeters and average 2175 eggs per gram. Young squid are thought to spawn in the Antarctic summer time when the water surface temperatures are −0.9–0 °C (30.4–32.0 °F).

Differences Between Giant Squids and Colossal Squids

Giant squids and colossal squids are the largest squids and the largest invertebrates but are different species. Giant squids belong to the genus Architeuthidae while colossal squids belong to the genus Mesonychoteuthis. [Source: AZ Animals]

Giant squids live around the world, in the Atlantic, Indian and Pacific Oceans while colossal squids live in very cold waters near Antarctica and the Southern Ocean exclusively. Giant squids live in deep waters, often more than 500 meters (1600 feet deep) in temperate seas, but rarely tropical or polar waters, Colossal squids are found only in polar seas, often at depths of more than 1000 meters 3300 feet deep.

Giant squids are 12 to 15 meters (40 to 50 feet) in length and weigh up to 300 kilograms (660 pounds). Colossal squids are 9 to 12 5 meters (30-40 feet) in length and weigh up to 500 kilograms (1,100 pounds). Giant squids have eight arms, two long tentacles with suckers and teeth; huge eyes and long narrow body. Colossal squids also have eight arms but have shorter tentacles with hooks used to catch prey. They also have a body that is shorter, stouter and wider than that of a giant squid

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated April 2023

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