Mesonychoteuthis hamiltoni

Geographic Range

Mesonychoteuthis hamiltoni occurs in the Southern Ocean from Antarctica to the southern tips of Africa, South America, and New Zealand. This species’ range coincides with the Antarctic Circumpolar Current. (Rodhouse and Clarke, 1986)


Juveniles of M. hamiltoni swim in the upper 1000 m of the ocean and have not been found below 1000 m. The early stages are concentrated beneath the surface layer in the upper zone of the warm deep water, perhaps because at this depth biological activity is high resulting from spikes in phytoplankton biomass. Because adult beaks have been found in the stomachs of sperm whales, the adults must have reach depths of at least 2200 m. (Evans and Hindell, 2004; O'Shea and Bolstad, 2000; Rodhouse and Clarke, 1986)

Physical Description

While no adults have been located or observed, M. hamiltoni may reach up to 14 m in length with a mantle length of 2-4 m. This species is the largest known invertebrate. The eyes can measure up to 30 cm in diameter, possibly the largest in the animal kingdom. These squid have the largest beaks of any squid, along with 25 rotating hooks that are aligned in two rows at the ends of their tentacles. (Rosa and Seibel, 2010)

  • Range length
    14 (high) m
    45.93 (high) ft


Not much is known about M. hamiltoni development because no adult organisms have ever been captured or observed.


Upon dissection of a mature male adult, there seems to be no hectocotylus, which in typical squids is the organ of sperm storage and transfer and is found at the end of one of the male’s tentacles. Instead, it is speculated that M. hamiltoni males have penises. (Clarke and Prince, 1976; O'Shea and Bolstad, 2000)

Little is known about the reproductive behavior of M. hamiltoni because no specimens have been observed live. In general, many squids have precopulatory rituals, and males seize females with their tentacles prior to mating. Fertilization is likely internal. (Brusca and Brusca, 2003)

Little is known about the reproductive behavior of M. hamiltoni because no specimens have been observed live.


No adult M. hamiltoni specimens have been discovered so the lifespan of the organism is currently unknown.


Mesonychoteuthis hamiltoni is thought to have a slow paced life because of its large size and low prey requirements. (Rosa and Seibel, 2010)

Communication and Perception

Mesonychoteuthis hamiltoni is likely a visual predator due to its extremely large eye which can reach up to about 30 cm in diameter. (O'Shea and Bolstad, 2000)

Food Habits

Mesonychoteuthis hamiltoni has low prey requirements and feeds on large fish including the Patagonian toothfish, Dissostichus eleginoides. One 5 kg toothfish may provide enough energy for a 500 kg squid to survive for up to 200 days. 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. Mesonychoteuthis hamiltoni is thought to be an ambush predator that depends on its hooks to catch prey. Because of its size and probable energy intake, it most likely does not expend energy actively chasing its prey. (Rosa and Seibel, 2010)

  • Animal Foods
  • fish


The sperm whale, Physeter catodon is a known predator of M. hamiltoni. Mesonychoteuthis hamiltoni may prey on or fight with P. catodon. (Evans and Hindell, 2004)

Ecosystem Roles

Currently, little if anything is known about its distinct role in the ecosystem.

Economic Importance for Humans: Positive

Not much is known about this species and any benefits that it might have on humans yet.

Economic Importance for Humans: Negative

There are no known adverse affects of M. hamiltoni on humans. Because of its remote range, it is unlikely that this species has much of a negative economic effect on humans. (Rodhouse and Clarke, 1986)

Conservation Status

Not enough is known on colossal squid populations to determine its conservation status.

  • IUCN Red List [Link]
    Not Evaluated


Dan Ravaioli (author), Rutgers University, Tracy Youngster (author), Rutgers University, David V. Howe (editor), Rutgers University, Renee Mulcrone (editor), Special Projects.



lives on Antarctica, the southernmost continent which sits astride the southern pole.


Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map


on or near the ocean floor in the deep ocean. Abyssal regions are characterized by complete lack of light, extremely high water pressure, low nutrient availability, and continuous cold (3 degrees C).

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


chemicals released into air or water that are detected by and responded to by other animals of the same species


an animal that mainly eats fish


the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.


uses sight to communicate


Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Clarke, M., P. Prince. 1976. Cephalopod remains in regurgitations of black-browned and gray-headed albatrosses at South Georgia. British Antarctic Survey Bulletin, 54: 1-7. Accessed February 27, 2012 at

Evans, K., M. Hindell. 2004. The diets of sperm whales (Physeter macrocephalus) in southern Australian waters. ICES Journal of Marine Science, 61: 1313-1329. Accessed March 02, 2012 at

O'Shea, S., K. Bolstad. 2000. "Giant Squid and Colossal Squid Fact Sheet" (On-line). Accessed February 27, 2012 at

Rodhouse, P., M. Clarke. 1986. Distribution of the early-life phase of the Antarctic squid Galitheuthis glacialis in relation to the hydrology of the southern ocean in the sector 15° to 30° E. Marine Biology, 91: 353-357. Accessed February 27, 2012 at

Rosa, R., B. Seibel. 2010. Slow pace of life of the Antarctic colossal squid. Journal of the Marine Biological Association of the United Kingdom, 90: 1375-1378.