The name of seven-armed octopus seems to contradict the usual anatomy of the group. Haliphron atlanticus has eight arms. In the male, the one used to transfer sperm can remain folded in a bag under the right eye, giving the impression that an appendix is missing.
Females can reach a much larger size than males. A meeting filmed in 2017 showed a female holding a jellyfish; the study of stomach contents of museum specimens confirmed the importance of gelatinous animals in her diet.
Researchers believe that the stinging tentacles preserved after the meal could also be used to defend themselves. The latter role remains an interpretation, unlike the number of arms. The nickname therefore remains useful for recognizing the animal, provided that it is not taken as an exact inventory of its body.
What we know
Eight real arms; likely defensive role of jellyfish tentacles, not certain.
To go to the source
References consulted on 3 October 2026. Linked pages may be in another language.
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