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, cuttle ...

; based on scientific records, it has a maximum estimated total length of and mass of . The only other similarly large

extant species Neontology is a part of biology that, in contrast to paleontology, deals with living (or, more generally, ''recent'') organisms. It is the study of extant taxa (singular: extant taxon): taxa (such as species, genera and families) with members st ...

is the giant Pacific octopus, ''

Enteroctopus dofleini The giant Pacific octopus (''Enteroctopus dofleini''), also known as the North Pacific giant octopus, is a large marine cephalopod belonging to the genus ''Enteroctopus''. Its spatial distribution includes the coastal North Pacific, along Mexico ...

''. 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 nomenclat ...

''Alloposina'' Grimpe, 1922, ''Alloposus'' Verrill, 1880 and ''Heptopus'' Joubin, 1929 are

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

s 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 Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Alloposidae, part of the superfamily Argonautoidea in the

suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

Incirrata of the order Octopoda.

Description

The seven-arm octopus is so named because in males, the

hectocotylus A hectocotylus (plural: ''hectocotyli'') is one of the arms of male cephalopods that is specialized to store and transfer spermatophores to the female. Structurally, hectocotyli are muscular hydrostats. Depending on the species, the male may use i ...

(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 wiktionary:en:specimen, 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 a ...

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's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

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 The Copenhagen Zoological Museum (Danish: ''Zoologisk Museum'') is a part of the Natural History Museum of Denmark, which is affiliated with the University of Copenhagen. History The Zoological Museum It is among the world's oldest natural hist ...

. 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 east� ...

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

Chatham Rise The Chatham Rise is an area of ocean floor to the east of New Zealand, forming part of the Zealandia continent. It stretches for some from near the South Island in the west, to the Chatham Islands in the east. It is New Zealand's most productive ...

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 count ...

. 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 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 The blue shark (''Prionace glauca''), also known as the great blue shark, is a species of requiem shark, in the family Carcharhinidae, which inhabits deep waters in the world's temperate and tropical oceans. Averaging around and preferring co ...

Hawaiian monk seal The Hawaiian monk seal (''Neomonachus schauinslandi'') is an endangered species of earless seal in the family Phocidae that is endemic to the Hawaiian Islands. The Hawaiian monk seal is one of two extant monk seal species; the other is the Med ...

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 Swordfish (''Xiphias gladius''), also known as broadbills in some countries, are large, highly migratory predatory fish characterized by a long, flat, pointed bill. They are a popular sport fish of the billfish category, though elusive. Swordfis ...

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