seven-arm octopus

{{Speciesbox

| image = Haliphron atlanticus (70 mm ML).jpg

| image_caption = Ventral view of young female (70 mm ML)

| image2 = Haliphron atlanticus1.jpg

| image2_caption = Lateral view of young male

| status = LC

| status_system = IUCN3.1

| status_ref = {{cite iucn |author=Allcock, L. |date=2014 |title=Haliphron atlanticus |volume=2014 |page=e.T163207A983527 |doi=10.2305/IUCN.UK.2014-3.RLTS.T163207A983527.en |access-date=19 November 2021}}

| grandparent_authority = Verrill, 1881

| genus = Haliphron

| parent_authority = Steenstrup, 1861

| species = atlanticus

| authority = Steenstrup, 1861{{cite web | url = http://www.marinespecies.org/aphia.php?p=taxdetails&id=137643 | title = Haliphron Steenstrup, 1859 | access-date = 5 February 2018 | publisher = Flanders Marine Institute | author = Julian Finn | year = 2017 | work = World Register of Marine Species}}

| synonyms ={{bulleted list

|Alloposus mollis {{small|(Verrill, 1880)}}

|?Octopus alberti {{small|(Joubin, 1895)}}

|Alloposus pacificus {{small|(Ijima & Ikeda, 1902)}}

|Heptopus danai {{small|(Joubin, 1929)}}

|Alloposus hardyi {{small|(Robson, 1930)}}

|?Alloposina albatrossi {{small|(Robson, 1932)}}

}}

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; the largest specimen ever discovered had an estimated total length of {{cvt|3.5|m|ft}} and mass of {{cvt|75|kg|lb}}.{{cite journal | last1 = O'Shea | first1 = S. | year = 2002 | title = Haliphron atlanticus — a giant gelatinous octopus | url =http://isopods.nhm.org/pdfs/27566/27566.pdf | journal = Biodiversity Update | volume = 5 | page = 1 }}{{cite journal | last1 = O'Shea | first1 = S. | year = 2004 | title = The giant octopus Haliphron atlanticus (Mollusca : Octopoda) in New Zealand waters | doi = 10.1080/03014223.2004.9518353 | journal = New Zealand Journal of Zoology | volume = 31 | issue = 1| pages = 7–13 | s2cid = 84954869 | doi-access = free }} The only other similarly large extant species is the giant Pacific octopus, Enteroctopus dofleini.

The genera Alloposina (Grimpe, 1922), Alloposus (Verrill, 1880) and Heptopus (Joubin, 1929) are junior synonyms of Haliphron, a monotypic genus in the monotypic family Alloposidae, part of the superfamily Argonautoidea in the suborder Incirrata of the order Octopoda.

Description

File:Haliphron atlanticus embryos.jpg ({{coord|17|24|N|22|57|W}}): The eggs measure around {{cvt|8|mm}} at their widest.]]

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.{{Cite web |date=2023-03-02 |title=About Live Science |url=https://www.livescience.com/about-live-science |access-date=2025-01-20 |website=livescience.com |language=en}}

Distribution

The type specimen of H. atlanticus was collected in the Atlantic Ocean at {{coord|38|N|34|W}} (west of the Azores). It is deposited at the University of Copenhagen Zoological Museum.[http://www.mnh.si.edu/cephs/newclass.pdf Current Classification of Recent Cephalopoda]

Since then, several specimens have been caught throughout the Atlantic, as far as the Azores archipelago{{cite journal | last1 = Rosa | first1 = R. | last2 = Kelly | first2 = J. | last3 = Lopes | first3 = V. | last4 = Paula | first4 = J. | last5 = Goncalves | first5 = J. | last6 = Calado | first6 = R. | last7 = Norman | first7 = M. | last8 = Barreiros | first8 = J. | year = 2017 | title = Deep-sea seven-arm octopus hijacks jellyfish in shallow waters | doi = 10.1007/s12526-017-0767-3 | journal = Marine Biodiversity | volume = 49| pages = 495–499 | s2cid = 255616524 }} and near South Georgia Island.{{cite journal | last1 = Guerreiro | first1 = M. | last2 = Phillips | first2 = R. | last3 = Cherel | first3 = Y. | last4 = Ceia | first4 = F. | last5 = Alvito | first5 = P. | last6 = Rosa | first6 = R. | last7 = Xavier | first7 = J. | year = 2015 | title = Habitat and trophic ecology of Southern Ocean cephalopods from stable isotope analyses | doi = 10.3354/meps11266 | url =https://www.int-res.com/articles/meps_oa/m530p119.pdf | journal = Marine Ecology Progress Series | volume = 530 | pages = 119–134 | bibcode = 2015MEPS..530..119G | doi-access = free }}

In 2002, a single specimen of giant proportions was caught by fishermen trawling at a depth of {{cvt|920|m}} off the eastern Chatham Rise, New Zealand. 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 {{cvt|0.69|m|ft}}, a total length of {{cvt|2.90|m|ft}}, and a weight of {{cvt|61.0|kg|lb}}, although it was incomplete.

Ecology

Isotopic, photographic and video evidence have shown complex interactions between H. atlanticus and jellyfish and other gelatinous zooplankton, from feeding to protection, respectively.

Predators of H. atlanticus include the blue shark, Hawaiian monk seal, sperm whale, and swordfish.{{cite journal |last1=Henderson |first1=A. C. |last2=Flannery |first2=K. |last3=Dunne |first3=J. |title=Observations on the biology and ecology of the blue shark in the North-east Atlantic |journal=Journal of Fish Biology |date=May 2001 |volume=58 |issue=5 |pages=1347–1358 |doi=10.1111/j.1095-8649.2001.tb02291.x}}{{cite journal |last1=Goodman-Lowe |first1=G. D. |title=Diet of the Hawaiian monk seal (Monachus schauinslandi) from the Northwestern Hawaiian islands during 1991 to 1994 |journal=Marine Biology |date=29 October 1998 |volume=132 |issue=3 |pages=535–546 |doi=10.1007/s002270050419|s2cid=84310964 }}{{cite journal |last1=Chua |first1=Marcus A.H. |last2=Lane |first2=David J.W. |last3=Ooi |first3=Seng Keat |last4=Tay |first4=Serene H.X. |last5=Kubodera |first5=Tsunemi |title=Diet and mitochondrial DNA haplotype of a sperm whale (Physeter macrocephalus) found dead off Jurong Island, Singapore |journal=PeerJ |date=5 April 2019 |volume=7 |pages=e6705 |doi=10.7717/peerj.6705|pmc=6452849 |pmid=30984481 |doi-access=free }}{{cite journal |last1=Clarke |first1=M.R. |last2=Pascoe |first2=P.L. |title=Cephalopod Species in the Diet of a Sperm Whale (Physeter Catodon) Stranded at Penzance, Cornwall |journal=Journal of the Marine Biological Association of the United Kingdom |date=11 May 2009 |volume=77 |issue=4 |pages=1255 |doi=10.1017/S0025315400038819|s2cid=86637228 }}{{cite journal |last1=Chancollon |first1=Odile |last2=Pusineri |first2=Claire |last3=Ridoux |first3=Vincent |title=Food and feeding ecology of Northeast Atlantic swordfish ( Xiphias gladius ) off the Bay of Biscay |journal=ICES Journal of Marine Science |date=1 September 2006 |doi=10.1016/j.icesjms.2006.03.013 |volume=63 |issue=6 |pages=1075–1085|doi-access=free }}

Beak morphology

{{multiple image

| align = center

| footer = Lower (left) and upper beaks of female Haliphron atlanticus (estimated 150 mm ML) in lateral view
{{3d glasses}}

| image1 = Haliphron atlanticus lower beak (side view).jpg

| width1 = {{#expr: (250 * 1000 / 642) round 0}}

| image2 = Haliphron atlanticus upper beak (side view).jpg

| width2 = {{#expr: (250 * 1000 / 934) round 0}}

}}

References

External links

[http://tolweb.org/tree?group=Alloposidae&contgroup=Argonautoid_families Tree of Life web project: Haliphron atlanticus]
[http://www.tonmo.com/science/haliphron/haliphron.php The giant octopus Haliphron atlanticus (Mollusca: Octopoda) in New Zealand waters]
[http://news.bbc.co.uk/2/hi/science/nature/1898313.stm BBC News: Giant octopus puzzles scientists]
[http://www.tonywublog.com/20091110/seven-arm-octopus.html Tony Wu Underwater Photography: Seven-arm octopus]

Category:Octopuses

Category:Molluscs of the Atlantic Ocean

Category:Molluscs of the Pacific Ocean

Category:Cephalopods of Oceania

Category:Cephalopods described in 1861

Category:Molluscs of the Azores