Invertebrates
Seven-arm Octopus
Haliphron atlanticus · also called seven-armed octopus
Hiding its eighth arm coiled inside a pouch beneath one eye, a seven-arm octopus drifts through open water preying heavily on jellyfish, quietly ranking among the largest and heaviest octopus species known despite its low public profile.
Overview
The seven-arm octopus, Haliphron atlanticus, is a large, soft-bodied cephalopod native to ocean habitat recorded across every major ocean basin worldwide. Its concealed eighth arm, jellyfish-heavy diet, and status as one of the largest and heaviest octopus species known make it one of the more physically impressive yet under-recognised cephalopods found anywhere in the ocean.
A giant hiding in plain sight
Despite ranking among the heaviest octopus species on record, the seven-arm octopus remains far less famous than smaller, more frequently encountered relatives, its open-water lifestyle and concealed eighth arm keeping it largely out of public view.
Status
Least Concern, though population trends remain largely unknown given the difficulty of surveying open-water habitat.
Seven-arm Octopus: common questions
Why does the seven-arm octopus appear to have only seven arms?
This species keeps its eighth arm, modified for reproduction in males, coiled up in a pouch beneath one eye, making the animal appear to have only seven arms rather than the usual eight found in other octopus species.
How big can a seven-arm octopus get?
This species ranks among the largest and heaviest known octopus species by weight, rivalling far better-known giants in overall mass despite receiving much less public attention than more famous large cephalopods.
What does the seven-arm octopus eat?
This species feeds substantially on jellyfish and other gelatinous animals, an unusual diet compared with many other octopus species, which typically favour crustaceans and molluscs found on or near the seafloor.
Does the seven-arm octopus live on the seafloor?
No, this species spends much of its life drifting through open ocean water rather than crawling across the seafloor, a lifestyle shared with several other large deep-sea cephalopods.