Blue-ringed octopus

Hapalochlaena sp.

Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Octopoda
Family: Octopodidae
Genus: Hapalochlaena
Species: Hapalochlaena sp.

The blue-ringed octopus (Hapalochlaena sp.) is a small but extremely venomous octopus that flashes electric blue rings when alarmed.

Only around 5-10 cm across, it carries tetrodotoxin powerful enough to be dangerous to humans, so it must never be touched. It hunts small crabs and shrimp among rubble.

Two blue-ringed octopuses are found in the Philippines: the greater blue-ringed octopus (Hapalochlaena lunulata) and a still-undescribed Hapalochlaena species. Both are sought-after finds on Philippine muck dives.