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Seven-arm octopus
Species of cephalopod

The seven-arm octopus (Haliphron atlanticus), also known as the blob octopus or septopus, is one of the two largest known species of octopus, with the largest specimen measuring 3.5 m (11 ft) and weighing 75 kg (165 lb). Alongside the giant Pacific octopus, Enteroctopus dofleini, it is among the largest extant species. The genus Haliphron is monotypic and belongs to the family Alloposidae, within the superfamily Argonautoidea. Several genera such as Alloposina, Alloposus, and Heptopus are considered junior synonyms of Haliphron, all classified under the suborder Incirrata of the order Octopoda.

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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.4

Distribution

The type specimen of H. atlanticus was collected in the Atlantic Ocean at 38°N 34°W / 38°N 34°W / 38; -34 (west of the Azores). It is deposited at the University of Copenhagen Zoological Museum.5

Since then, several specimens have been caught throughout the Atlantic, as far as the Azores archipelago6 and near South Georgia Island.7

In 2002, a single specimen of giant proportions was caught by fishermen trawling at a depth of 920 m (3,020 ft) 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 0.69 m (2.3 ft), a total length of 2.90 m (9.5 ft), and a weight of 61.0 kg (134.5 lb), although it was incomplete.89

Ecology

Isotopic,10 photographic and video evidence11 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.1213141516

Beak morphology

Lower (left) and upper beaks of female Haliphron atlanticus (estimated 150 mm ML) in lateral view 3D red cyan glasses are recommended to view this image correctly.

See also

Further reading

  • Bakken, T. & T. Holthe 2002. Haliphron atlanticum (Cephalopoda, Alloposidae) caught in Skorafjorden (64°N), Norway. Fauna norv. 22: 37–38.
  • Willassen, E (1986). "Haliphron atlanticus Steenstrup (Cephalopoda: Octopoda) from the coast of Norway". Sarsia. 71: 35–40. doi:10.1080/00364827.1986.10419671.

References

  1. O'Shea, S. (2002). "Haliphron atlanticus — a giant gelatinous octopus" (PDF). Biodiversity Update. 5: 1. http://isopods.nhm.org/pdfs/27566/27566.pdf ↩

  2. O'Shea, S. (2004). "The giant octopus Haliphron atlanticus (Mollusca : Octopoda) in New Zealand waters". New Zealand Journal of Zoology. 31 (1): 7–13. doi:10.1080/03014223.2004.9518353. S2CID 84954869. https://doi.org/10.1080%2F03014223.2004.9518353 ↩

  3. Julian Finn (2017). "Haliphron Steenstrup, 1859". World Register of Marine Species. Flanders Marine Institute. Retrieved 5 February 2018. http://www.marinespecies.org/aphia.php?p=taxdetails&id=137643 ↩

  4. "About Live Science". livescience.com. 2023-03-02. Retrieved 2025-01-20. https://www.livescience.com/about-live-science ↩

  5. Current Classification of Recent Cephalopoda http://www.mnh.si.edu/cephs/newclass.pdf ↩

  6. Rosa, R.; Kelly, J.; Lopes, V.; Paula, J.; Goncalves, J.; Calado, R.; Norman, M.; Barreiros, J. (2017). "Deep-sea seven-arm octopus hijacks jellyfish in shallow waters". Marine Biodiversity. 49: 495–499. doi:10.1007/s12526-017-0767-3. S2CID 255616524. /wiki/Doi_(identifier) ↩

  7. Guerreiro, M.; Phillips, R.; Cherel, Y.; Ceia, F.; Alvito, P.; Rosa, R.; Xavier, J. (2015). "Habitat and trophic ecology of Southern Ocean cephalopods from stable isotope analyses" (PDF). Marine Ecology Progress Series. 530: 119–134. Bibcode:2015MEPS..530..119G. doi:10.3354/meps11266. https://www.int-res.com/articles/meps_oa/m530p119.pdf ↩

  8. O'Shea, S. (2002). "Haliphron atlanticus — a giant gelatinous octopus" (PDF). Biodiversity Update. 5: 1. http://isopods.nhm.org/pdfs/27566/27566.pdf ↩

  9. O'Shea, S. (2004). "The giant octopus Haliphron atlanticus (Mollusca : Octopoda) in New Zealand waters". New Zealand Journal of Zoology. 31 (1): 7–13. doi:10.1080/03014223.2004.9518353. S2CID 84954869. https://doi.org/10.1080%2F03014223.2004.9518353 ↩

  10. Guerreiro, M.; Phillips, R.; Cherel, Y.; Ceia, F.; Alvito, P.; Rosa, R.; Xavier, J. (2015). "Habitat and trophic ecology of Southern Ocean cephalopods from stable isotope analyses" (PDF). Marine Ecology Progress Series. 530: 119–134. Bibcode:2015MEPS..530..119G. doi:10.3354/meps11266. https://www.int-res.com/articles/meps_oa/m530p119.pdf ↩

  11. Rosa, R.; Kelly, J.; Lopes, V.; Paula, J.; Goncalves, J.; Calado, R.; Norman, M.; Barreiros, J. (2017). "Deep-sea seven-arm octopus hijacks jellyfish in shallow waters". Marine Biodiversity. 49: 495–499. doi:10.1007/s12526-017-0767-3. S2CID 255616524. /wiki/Doi_(identifier) ↩

  12. Henderson, A. C.; Flannery, K.; Dunne, J. (May 2001). "Observations on the biology and ecology of the blue shark in the North-east Atlantic". Journal of Fish Biology. 58 (5): 1347–1358. doi:10.1111/j.1095-8649.2001.tb02291.x. /wiki/Doi_(identifier) ↩

  13. Goodman-Lowe, G. D. (29 October 1998). "Diet of the Hawaiian monk seal (Monachus schauinslandi) from the Northwestern Hawaiian islands during 1991 to 1994". Marine Biology. 132 (3): 535–546. doi:10.1007/s002270050419. S2CID 84310964. /wiki/Doi_(identifier) ↩

  14. Chua, Marcus A.H.; Lane, David J.W.; Ooi, Seng Keat; Tay, Serene H.X.; Kubodera, Tsunemi (5 April 2019). "Diet and mitochondrial DNA haplotype of a sperm whale (Physeter macrocephalus) found dead off Jurong Island, Singapore". PeerJ. 7: e6705. doi:10.7717/peerj.6705. PMC 6452849. PMID 30984481. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6452849 ↩

  15. Clarke, M.R.; Pascoe, P.L. (11 May 2009). "Cephalopod Species in the Diet of a Sperm Whale (Physeter Catodon) Stranded at Penzance, Cornwall". Journal of the Marine Biological Association of the United Kingdom. 77 (4): 1255. doi:10.1017/S0025315400038819. S2CID 86637228. /wiki/Doi_(identifier) ↩

  16. Chancollon, Odile; Pusineri, Claire; Ridoux, Vincent (1 September 2006). "Food and feeding ecology of Northeast Atlantic swordfish ( Xiphias gladius ) off the Bay of Biscay". ICES Journal of Marine Science. 63 (6): 1075–1085. doi:10.1016/j.icesjms.2006.03.013. https://doi.org/10.1016%2Fj.icesjms.2006.03.013 ↩