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 3.5 m (11 ft) and mass of 75 kg (165 lb).[3][4] The only other similarly large
extant species is the giant Pacific octopus, Enteroctopus dofleini.
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.[citation needed]
Since then, several specimens have been caught throughout the Atlantic, as far as the
Azores archipelago[6] 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 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.[3][4]
Ecology
Isotopic,[7] photographic and video evidence[6] have shown complex interactions between H. atlanticus and
jellyfish and other gelatinous zooplankton, from feeding to protection, respectively.
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.
^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.
^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.
S2CID84310964.
^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.
S2CID86637228.
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.