A poison-ocellate octopus with a single dark eyespot on each side, usually in bottles or crevices.
Mantle to about 10 cm and total length to around 32 cm. At rest it is a drab orange-cream-brown with black papillae above each eye; disturbed, it produces a striking alarm display of maroon stripes over white across the body and arms. The identifying structure is a pair of iridescent blue-ringed ocelli, one on each side at the base of the web, functioning as false eyes. Two confusions matter. Against the coconut octopus: the ocelli are present here and absent there. Against a blue-ringed octopus — the error that actually matters — this animal has exactly two large ocelli, one per side, where a blue-ringed octopus carries some sixty small rings scattered over the mantle and arms, and this is a much larger, longer-armed animal.
Crepuscular. It excavates deep lairs under coral heads and in rubble on sand, and its dens are characteristically ringed with discarded gastropod shells, which may be accumulated to draw in hermit crabs — a suggestion in the literature rather than a finding. The diet is heavily crustacean; it drills gastropod shells and injects paralysing saliva before extracting the animal. It is unusually willing to bite objects, which is uncommon among octopuses. On the reputation: the name “poison ocellate octopus” comes from a Polynesian vernacular name and from the warning colours, not from a toxicology result. No assay for tetrodotoxin in this species appears to have been published, and no human envenomation by it is documented. All octopuses have venomous saliva and this one is more inclined than most to use its beak, which is reason enough not to handle it — but it is not, on present evidence, a blue-ringed octopus.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
