The seven-arm octopus (''Haliphron atlanticus''), also known as the blob octopus or sometimes called septopus, is one of the two largest known species of

octopus An octopus (: octopuses or octopodes) 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, cuttlefish, and nautiloids. Like oth ...

; the largest specimen ever discovered had an 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, studies and 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) wi ...

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'' and Enteroctopodidae family. Its spatial distribution encompasses much o ...

''. The

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

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

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

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 "unisp ...

genus in the monotypic

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Alloposidae, part of the superfamily Argonautoidea in the

suborder Order () 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 recognized ...

Incirrata of the order Octopoda.

Description

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

hectocotylus A hectocotylus (: 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 it merel ...

(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 wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

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

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 ...

at (west of the

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

). It is deposited at the

University of Copenhagen Zoological Museum The Copenhagen Zoological Museum ( Danish: ''Zoologisk Museum'') was a separate zoological museum in Copenhagen, Denmark. It is now a part of the Natural History Museum of Denmark, which is affiliated with the University of Copenhagen. The separa ...

. Since then, several specimens have been caught throughout the Atlantic, as far as the

archipelago and near

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. ...

. In 2002, a single specimen of giant proportions was caught by fishermen trawling at a depth of 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 productiv ...

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 ...

. 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, also known as sea jellies or simply jellies, are the #Life cycle, medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animal ...

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 and the only member of its genus which inhabits deep waters in the world's temperate and tropical oceans. Ave ...

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 ...

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 ...

, and

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 ...

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