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 Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''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 reach a mass of at least , though the largest specimens—known only from beaks found in

sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the Genus (biology), genus ''Physeter'' and one of three extant species in the s ...

stomachs—may perhaps weigh as much as , making it the largest extant

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

. Maximum total length is ~. Larger estimates exist, however these include the feeding tentacles measured on dead specimens as in life the squid’s tentacles are hidden, only released when capturing prey. If tentacles are considered, lengths of and exist, but the former estimate is more likely.Roper, C.F.E. & P. Jereb (2010). Family Cranchiidae. In: P. Jereb & C.F.E. Roper (eds.)
Cephalopods of the world. An annotated and illustrated catalogue of species known to date. Volume 2. Myopsid and Oegopsid Squids
'. FAO Species Catalogue for Fishery Purposes No. 4, Vol. 2. FAO, Rome. pp. 148–178. The colossal squid has the largest eyes of any known creature ever to exist, with an estimated diameter of to for the largest collected specimen. The species has similar anatomy to 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 The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...

. It is presumed to be an

ambush predator Ambush predators or sit-and-wait predators are carnivorous animals that capture their prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey u ...

, with a diet including various fish, and is likely a key prey item of the sperm whale.

Morphology

The colossal

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

shares features common to all squids: a mantle for locomotion, one pair of gills, a beak or tooth, and certain external characteristics like eight arms and two tentacles, a head, and two fins. In general, the morphology and anatomy of the colossal squid are the same as any other squid. However, there are certain morphological characteristics that separate the colossal squid from other squids in its family: the colossal squid is the only squid in its family whose arms and tentacles are equipped with hooks, either swiveling or three-pointed. There are squids in other families that also have hooks, but no other squid in the family Cranchiidae. Calmarcolossal

Unlike most squid species, the colossal squid exhibits abyssal gigantism, as it is the heaviest living invertebrate species, reaching weights up to . For comparison, squids typically have a mantle length of about and weigh about . The colossal squid also has the largest eyes documented in the animal kingdom, with a diameter of .

Distribution and habitat

The squid's known range extends thousands of kilometres north of

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

to southern

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

, southern

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

, and the southern tip of

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, making it primarily an inhabitant of the circumantarctic

. Colossal squid are also often sighted near Cooperation Sea and

Ross Sea The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land and within the Ross Embayment, and is the southernmost sea on Earth. It derives its name from the British explorer James Clark Ross who ...

because of its prey and competitor, the Antarctic toothfish. The region between the

Weddell Sea The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha C ...

and the western Kerguelen archipelago has been deemed a "hotspot" based on characteristics of the habitat. The squid's vertical distribution appears to correlate directly with age. Young squid are found between , adolescent squid are found and adult squid are found primarily within the

mesopelagic The mesopelagic zone (Greek language, Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light ...

and bathypelagic regions of the open ocean.

Behavior

Feeding

While little is known about their behavior, colossal squid are believed to feed primarily on small fish, such as

lanternfish Lanternfish (or myctophids, from the Greek language, Greek μυκτήρ ''myktḗr'', "nose" and ''ophis'', "serpent") are small mesopelagic fish of the large family (biology), family Myctophidae. One of two families in the order Myctophiformes, ...

and deep-sea smelt, which have been found as stomach contents in adult specimens. They also attack larger fish; of 8,000 Antarctic toothfish brought aboard by 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. Studies measuring the δ¹⁵N content of the

chitin Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...

ous beaks of cephalopods to determine trophic ecology levels have demonstrated that the colossal squid is a top predator that is positively correlated with its increased size. This new confirmation of the colossal squid's trophic level suggests that it likely preys on large fishes and smaller squids, according to its size, and that its predators include

s and sleeper sharks.

Metabolism

The colossal squid is thought to have a very slow metabolic rate, needing only around of prey daily for an adult with a mass of . Estimates of its energy requirements suggest it is a slow-moving

, using its large eyes primarily for prey-detection rather than engaging in active hunting.

Predation

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

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

consumed by these whales. Many other animals also feed on colossal squid, including the

beaked whale Beaked whales (systematic name Ziphiidae) are a Family (biology), family of cetaceans noted as being one of the least-known groups of mammals because of their deep-sea habitat, reclusive behavior and apparent low abundance. Only three or four of ...

s, such as southern bottlenose whales, and Cuvier's and Baird's beaked whales. Other possible predators include the

pilot whale Pilot whales are cetaceans belonging to the genus ''Globicephala''. The two Extant taxon, extant species are the long-finned pilot whale (''G. melas'') and the short-finned pilot whale (''G. macrorhynchus''). The two are not readily distinguish ...

, killer whales, larger southern elephant seals, Patagonian toothfish, southern sleeper sharks (''Somniosus antarcticus''), Antarctic toothfish, and

albatross Albatrosses, of the biological family Diomedeidae, are large seabirds related to the procellariids, storm petrels, and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Paci ...

es (e.g., the wandering and sooty albatrosses). Beaks from mature adults have only been recovered from large predators (i.e. sperm whales and southern sleeper sharks), while other predators only eat juveniles or young adults.

Reproduction

Not much is known about the colossal squid's reproductive cycle, although it does have two distinct sexes. Many species of squid, however, develop sex-specific organs as they age and develop. The adult female colossal squid has been discovered in much shallower waters, which likely implies that females spawn in shallower waters, rather than their usual depth. Additionally, the colossal squid has a high possible

fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the capability to produc ...

reaching over 4.2 million

oocyte An oocyte (, oöcyte, or ovocyte) is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ger ...

s, which is quite high compared to other squids in such cold waters. Colossal squid oocytes have been observed at sizes ranging from as large as 3.2x2.1 mm to as small as 1.4x0.5 mm. Sampling of colossal squid ovaries show an average of 2175 eggs per gram. Young squid are thought to spawn near the summer time at surface temperatures of .

Vision

For pelagic organisms of similar weight to the colossal squid, such as the

swordfish The swordfish (''Xiphias gladius''), also known as the broadbill in some countries, are large, highly migratory predatory fish characterized by a long, flat, pointed bill. They are the sole member of the Family (biology), family Xiphiidae. They ...

, the average eye diameter required for visual detection is 10 cm, but the colossal squid's are as large as . This allowed for an increase in visual detection strategies, including reduced diffraction blurring and greater contrast distinction, which must be extremely beneficial to the colossal squid to justify the large energetic expenses to grow, move, camouflage, and maintain these eyes. The colossal squid's increased pupil size has been mathematically proven to overcome the visual complications of the

pelagic zone The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

(the combination of downwelling daylight,

bioluminescence Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorgani ...

, and light scattering with increasing distance), especially by monitoring larger volumes of water at once and by detecting long-range changes in

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

bioluminescence via the physical disruption of large moving objects (e.g., sperm whales). The colossal squid's eyes glow in the dark via long, rectangular 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. It is hypothesized that the colossal squid's eyes can detect predator movement beyond 120 m, which is the upper limit of the sperm whale's sonar range.

Hearing

Squid have been found to detect the movement of sound waves via organs called

statocyst The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, crustaceans, and gastropods, A similar structure is also found in '' Xenoturbella''. T ...

s (similar to the human

cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus (cochlea), modiolus. A core component of the cochlea is the organ of Cort ...

). Squid statocysts likely respond to low-frequency sounds less than 500 Hz, similar to pelagic fish. Colossal squid are likely essentially deaf to high frequencies, such as whale

sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances ( ranging), communicate with or detect objects o ...

, so they rely largely on visual detection mechanisms to avoid predation.

History of knowledge

The colossal squid, species ''Mesonychoteuthis hamiltoni'', was discovered in 1925. This species belongs to the class

Cephalopoda A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, ...

and family Cranchiidae. In 1981, an adult specimen was discovered; in 2003, a second specimen was collected. Captured in 2007, the largest colossal squid weighed , and is now on display at the Museum of New Zealand Te Papa Tongarewa. Most of the time, full colossal squid specimens are not collected; as of 2015, only 12 complete colossal squids had ever been recorded, with only half of these being full adults. Beak remnants of the colossal squid are commonly collected; 55 beaks of colossal squids have been recorded in total. Less commonly (four times), a fin, mantle, arm or tentacle of a colossal squid has been collected.

First collected specimens

The species was first discovered in the form of two arm crowns found in the stomach of a

in the winter of 1924–1925. This species, named ''Mesonychoteuthis hamiltoni'' after E. Hamilton who made the initial discovery, was formally described by Guy Coburn Robson in 1925.

Entire collected specimens

In 1981, a Soviet Russian trawler in the

, off the coast of

, caught a large squid with a total length of over , which was later identified as an immature female of ''M. hamiltoni''.Ellis, R. 1998. '' The Search for the Giant Squid''. The Lyons Press. In 2003, a complete specimen of a subadult female was found near the surface with a total length of and a mantle length of 2.5 m (8 feet 3 inches). In 2005, the first full living specimen was captured at a depth of while taking a toothfish from a longline off

South Georgia Island South Georgia is an island in the Atlantic Ocean, South Atlantic Ocean that is part of the British Overseas Territories, British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. ...

. Although the mantle was not brought aboard, its length was estimated at over 2.5 m (8 feet 3 inches), and the tentacles measured . The animal is thought to have weighed between .

Largest known specimen

The largest recorded specimen was a female, which are thought to be larger than males, captured in February 2007 by a New Zealand fishing boat in the

off Antarctica. The squid was close to death when it was captured and subsequently was taken back to New Zealand for scientific study. The specimen was initially estimated to measure about 10 metres in total length and weigh about 450 kg.

Defrosting and dissection, April–May 2008

Thawing and dissection of the specimen took place at the Museum of New Zealand Te Papa Tongarewa. AUT biologist Steve O'Shea, Tsunemi Kubodera, and AUT biologist Kat Bolstad were invited to the museum to aid in the process, joined by Marine Ecologist Mark Fenwick and Dutch scientist Olaf Blaauw.Te Papa's Specimen: The Thawing and Examination
. Tepapa.govt.nz. Retrieved on 30 September 2011. Media reports suggested scientists at the museum were considering using a giant microwave to defrost the squid because thawing it at room temperature would take several days and it would likely begin to decompose on the outside while the core remained frozen. However, they later opted for the more conventional approach of thawing the specimen in a bath of salt water. After thawing, it was found that the specimen was 495 kg with a mantle length of 2.5 m and a total length of only 4.2 m, probably because the tentacles shrank once the squid was dead. Parts of the specimen have been examined: *The beak is considerably smaller than some found in the stomachs of

s, suggesting that some other colossal squid are much larger than this one. *The eye is wide, with a lens across. This is the largest eye of any known animal. These measurements are of the partly collapsed specimen; when the squid was alive, the eye was probably 30 to 40 cm (12 to 16 in) across. *Inspection of the specimen with an endoscope revealed

ovaries The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are endocr ...

containing thousands of eggs.

Exhibition

The Museum of New Zealand Te Papa Tongarewa began displaying this specimen from 13 December 2008. The exhibition was closed between 2018 and 2019, but it was reopened for public viewing at Te Papa.

Filming in natural habitat

In 2022–23 there were several attempts made by scientists, including an ocean exploration non-profit called KOLOSSAL, to find and film the colossal squid in its natural habitat for the first time to learn more about its biology and ecological behavior. The science team used a tourism vessel to survey 36 locations throughout the Southern Ocean and may have filmed a small juvenile colossal squid for the first time. Researchers have confirmed that that video is of a species of glass squid, but due to

marine snow In the deep ocean, marine snow (also known as "ocean dandruff") is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to ...

, the footage has been harder to confirm without a DNA analysis, and may instead represent '' Galiteuthis glacialis'' or a new species of glass squid unknown to science. On 9 March 2025, for the first time, a confirmed colossal squid was filmed in its natural environment during an expedition near the

South Sandwich Islands The South Sandwich Islands () are a chain of uninhabited volcanic islands in the South Atlantic Ocean. They are administered as part of the British Overseas Territory of South Georgia and the South Sandwich Islands. The chain lies in the sub-A ...

in the South

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

. The squid, a juvenile measuring around long, was captured on video at a depth of by the Schmidt Ocean Institute's remotely operated vehicle (ROV) SuBastian.

Conservation status

The colossal squid has been assessed as a species of "

least concern A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...

" on the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...

. Colossal squid are not targeted by fishers; rather, they are only caught when they attempt to feed on fish caught on hooks. Additionally, due to their habitat, interactions between humans and colossal squid are considered rare.

References

External links

Tree of Life web project: ''Mesonychoteuthis hamiltoni''

Museum of New Zealand Te Papa Tongarewa(Te Papa) Colossal Squid Specimen Information

Museum of New Zealand Te Papa Tongarewa(Te Papa) Colossal Squid Images and Video

Tonmo.com: Giant Squid and Colossal Squid Fact Sheet

''New Zealand Herald'': Fishermen haul in world's biggest squid

BBC: Super squid surfaces in Antarctic

MarineBio: ''Mesonychoteuthis hamiltoni''
{{Taxonbar, from=Q378330, from2=Q2345488 Taoniinae Molluscs of the Southern Ocean Fauna of Antarctica Bioluminescent molluscs Cenozoic cephalopods Pliocene molluscs Cephalopods described in 1925