The colossal squid (''Mesonychoteuthis hamiltoni'') is part of the family

Cranchiidae The family Cranchiidae comprises the approximately 60 species of glass squid, also known as cockatoo squid, cranchiid, cranch squid, or bathyscaphoid squid. Cranchiid squid occur in surface and midwater depths of open oceans around the world. The ...

. 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 Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

''Mesonychoteuthis'' and is known from only a small number of specimens. 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 ''Physeter'' and one of three extant species in the sperm whale famil ...

stomachs—may perhaps weigh as much as ,

e Papa "" (English: "Oh, Uncle Waiari"), also known as "" is a traditional Māori song, often used in tītī tōrea, a type of whakaraka (skill and dexterity game) played by passing tītī (40-60cm long sticks) while seated, in time to a rhythmic so ...

(2019)
How big is the colossal squid on display?

Museum of New Zealand Te Papa Tongarewa The Museum of New Zealand Te Papa Tongarewa is New Zealand's national museum and is located in Wellington. ''Te Papa Tongarewa'' translates literally to "container of treasures" or in full "container of treasured things and people that spring f ...

(2019)
The beak of the colossal squid

. making it the largest known

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...

. Maximum total length has been estimated at .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. 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 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 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-smal ...

. Although little is known about the behaviour, it is known to use

bioluminescence Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some b ...

to attract prey. It is presumed to be an

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

, 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 colossal squid weighed , and is now on display with a second specimen at the

Morphology

The colossal

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fittin ...

shares features common to all squids: a mantle for locomotion, one pair of gills, and certain external characteristics like eight arms and two tentacles, a head, and two fins. In general, it is safe to describe the morphology and anatomy of the colossal squid the same way one would describe any other squid. However, there are certain morphological / anatomical characteristics that separate the colossal squid from other squids in its family: 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

Unlike most squid species, the colossal squid exhibits abyssal gigantism; it is the heaviest living invertebrate species, reaching weights up to . For comparison, squids typically have a mantle length of about and weigh about . Compared to the

giant squid The giant squid (''Architeuthis dux'') is a species of deep-ocean dwelling squid in the family Architeuthidae. It can grow to a tremendous size, offering an example of abyssal gigantism: recent estimates put the maximum size at around Tra ...

, which also exhibits deep-sea gigantism, the colossal squid is heavier. One evidence is that an analysis of the beaks of other specimens from the stomach of sperm whales have shown proof that it is likely that colossal squids much heavier (up to ) exist. The colossal squid also has the largest eyes documented in the animal kingdom, with an estimated 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, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

to southern

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

, southern

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

, and the southern tip of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

, making it primarily an inhabitant of the entire circumantarctic

. Colossal squid are also sighted often near

Cooperation Sea Cooperation Sea, also called Commonwealth Sea (erratum) or Sodruzhestvo Sea (russian: Море Содружества), is a proposed sea name for part of the Southern Ocean, between Enderby Land (the eastern limit of which is 59°34'E) and West I ...

and less near

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 predator and competitor, the

Antarctic toothfish The Antarctic toothfish (''Dissostichus mawsoni'') is a large, black or brown fish found in very cold (subzero) waters of the Southern Ocean near Antarctica. It is the largest fish in the Southern Ocean, feeding on shrimp and smaller fish, and pr ...

. 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 ...

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 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 begins at ...

and

bathypelagic The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagi ...

regions of the open ocean.

Behavior

Feeding

Little is known about their behaviour, but it is believed to feed on prey such as

chaetognatha The Chaetognatha or chaetognaths (meaning ''bristle-jaws'') are a phylum of predatory marine worms that are a major component of plankton worldwide. Commonly known as arrow worms, about 20% of the known Chaetognatha species are benthic, and ca ...

, large

fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

such as the

Patagonian toothfish The Patagonian toothfish (''Dissostichus eleginoides'') is a species of notothen found in cold waters () between depths of in the southern Atlantic, Pacific, and Indian Oceans and Southern Ocean on seamounts and continental shelves around most ...

, and smaller squid in the deep

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wor ...

using

. A recent study by Remeslo, Yakushev and Laptikhovsky revealed that

make up a significant part of the colossal squid's diet; of the 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 Prydz Bay is a deep embayment of Antarctica between the Lars Christensen Coast and Ingrid Christensen Coast. The Bay is at the downstream end of a giant glacial drainage system that originates in the East Antarctic interior. The Lambert Glacie ...

region of Antarctica found squid remains in a female colossal squid's stomach, suggesting the possibility of

cannibalism Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...

within this species. Studies measuring the δ15N content of the

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

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 Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

, 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, 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 make up 77% of the

biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...

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

beaked whale Beaked whales ( systematic name Ziphiidae) are a family of cetaceans noted as being one of the least known groups of mammals because of their deep-sea habitat and apparent low abundance. Only three or four of the 24 species are reasonably well- ...

s (such as the

southern bottlenose whale The southern bottlenose whale (''Hyperoodon planifrons'') is a species of whale, in the Ziphiid family, one of two members of the genus ''Hyperoodon''. Seldom observed, the southern bottlenose whale is resident in Antarctic waters. The species w ...

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

southern elephant seal The southern elephant seal (''Mirounga leonina'') is one of two species of elephant seals. It is the largest member of the clade Pinnipedia and the order Carnivora, as well as the largest extant marine mammal that is not a cetacean. It gets its ...

, southern sleeper sharks (''Somniosus antarcticus''),

, 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 Pac ...

es (e.g., the wandering and

sooty albatross The sooty albatross, dark-mantled sooty albatross or dark-mantled albatross,BirdLife International (2008b) (''Phoebetria fusca''), is a species of bird in the albatross family. They breed on sub-Antarctic islands and range at sea across the S ...

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

Reproduction

Little is known about the colossal squid's reproductive cycle although the colossal squid 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 than their normal 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 natural capability to pr ...

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 ...

s which is quite unique 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 average eye diameter required for visual detection is 10 cm, but colossal squid's are as large as 27 cm. The allowed increase in visual detection strategies, including reduced diffraction blurring and greater contrast distinction, 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 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 (e.g., sperm whales). The colossal squid's eyes glow in the dark via long rectangularly shaped light-producing

photophore A photophore is a glandular organ that appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors, ...

s located next to the lens on the front of both eyeballs.

Symbiotic bacteria Symbiotic bacteria are bacteria living in symbiosis with another organism or each other. For example, rhizobia living in root nodules of legumes provide nitrogen fixing activity for these plants. Symbiosis was first defined by Marko de Bary in 1869 ...

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

Although squid cannot hear sound, they can 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, and crustaceans. A similar structure is also found in '' Xenoturbella''. The statocyst c ...

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. A core component of the cochlea is the Organ of Corti, the sensory o ...

). Squid statocysts likely respond to low frequency sounds less than 500 Hz, similar to pelagic fish. Colossal squid are essentially deaf to high frequencies (like 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 on o ...

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

Taxonomy and history

The colossal squid, species ''Mesonychoteuthis hamiltoni'', was discovered in 1925. This species belongs to the class Cephalopoda and family Cranchiidae. 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. Commonly, beak remnants of the colossal squid are 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 was collected.

Notable discoveries

First 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, then named ''Mesonychoteuthis hamiltoni'' after E. Hamilton who made the initial discovery, was formally described by Guy Coburn Robson in 1925.

Entire 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 Search for the Giant Squid'' is a non-fiction book by Richard Ellis on the biology, history and mythology of the giant squid of the genus '' Architeuthis''. It was well received upon its release in 1998. Though soon rendered outdated by i ...

''. 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 ''Dissostichus'', the toothfish, is a genus of marine ray-finned fish belonging to the family Nototheniidae, the notothens or cod icefish. These fish are found in the Southern Hemisphere. Toothfish are marketed in the United States as Chilea ...

from a longline off

South Georgia Island South Georgia ( es, Isla San Pedro) is an island in the South Atlantic Ocean that is part of the British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. Stretching in the east� ...

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

= Defrosting and dissection, April–May 2008

= Thawing and dissection of the specimen took place at the

. AUT biologist

Steve O'Shea Steve O'Shea (born 14 December 1965 in Auckland, New Zealand) is a marine biologist and environmentalist known for his research on giant squid. O'Shea obtained his degrees from Auckland university. He undertook a Bachelor of Science between 1984 ...

Tsunemi Kubodera is a Japanese zoologist with the National Museum of Nature and Science. On September 30, 2004, Kubodera and his team became the first people to ''photograph'' a live giant squid in its natural habitat.Kubodera, T. & K. Mori 2005First-ever observa ...

, and AUT biologist Kat Bolstad were invited to the museum to aid in the process.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 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 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; 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 an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

containing thousands of eggs.

=Exhibition

= The

began displaying this specimen in an exhibition that opened on 13 December 2008; however the exhibition was closed in 2018 and was slated to return in 2019. The exhibition is now open again for public viewing at Te Papa.

Second specimen

In August 2014, Te Papa received a second colossal squid, captured in early 2014. The specimen was also female, measuring long and weighing approximately .

Conservation status

The colossal squid has been assessed as "

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

" 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 the world's most comprehensive inventory of the global conservation status of biolo ...

. Furthermore, colossal squid are not targeted by fishermen; 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 Squid Fauna of the Southern Ocean Fauna of Antarctica Bioluminescent molluscs Cenozoic cephalopods Pliocene animals Molluscs described in 1925