The seven-arm octopus (''Haliphron atlanticus'') is one of the two largest known species of

octopus An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefis ...

; based on scientific records, it has a maximum estimated total length of and mass of . The only other similarly large extant species is the giant Pacific octopus, '' Enteroctopus dofleini''. The

genera 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 ...

''Alloposina'' Grimpe, 1922, ''Alloposus'' Verrill, 1880 and ''Heptopus'' Joubin, 1929 are junior synonyms of ''Haliphron'', a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus in the monotypic

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Alloposidae, part of the superfamily Argonautoidea in the suborder Incirrata of the order Octopoda.

Description

The seven-arm octopus is so named because in males, the hectocotylus (a specially modified arm used in egg fertilization) is coiled in a sac beneath the right eye. Due to this species' thick, gelatinous tissue, the arm is easily overlooked, giving the appearance of just seven arms. However, like other octopuses, it actually has eight.

Distribution

The

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

of ''H. atlanticus'' was collected in the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

at (west of the

Azores ) , motto= ( en, "Rather die free than subjected in peace") , anthem=( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...

). It is deposited at the University of Copenhagen Zoological Museum. Since then, several specimens have been caught throughout the Atlantic, as far as the

archipelago and near

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 eas ...

. In 2002, a single specimen of giant proportions was caught by fishermen trawling at a depth of 920 m off the eastern Chatham Rise,

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 List of islands of New Zealand, smaller islands. It is the ...

. This specimen, the largest of this species and of all octopuses, was the first validated record of ''Haliphron'' from the South Pacific. It had a

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

length of , a total length of , and a weight of , although it was incomplete.

Ecology

Isotopic, photographic and video evidence have shown complex interactions between ''H. atlanticus'' and

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

and other gelatinous zooplankton, from feeding to protection, respectively. Predators of ''H. atlanticus'' include the blue shark, Hawaiian monk seal,

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 ...

, and swordfish.

Beak morphology

References

External links

Tree of Life web project: ''Haliphron atlanticus''The giant octopus ''Haliphron atlanticus'' (Mollusca: Octopoda) in New Zealand watersBBC News: Giant octopus puzzles scientists
{{Taxonbar, from=Q603484 Octopuses Molluscs of the Atlantic Ocean Molluscs of the Pacific Ocean Cephalopods of Oceania Cephalopods described in 1861 Molluscs of the Azores