The blue-ringed octopus has venom.
The blue-lined octopus ( Hapalochlaena fasciata ) is one of three ( or perhaps four ) species of venomous Blue-ringed octopuses . Blue-ringed octopus . They are recognized as one of the world 's most venomous marine animals . Despite their small size , 12 to , and relatively docile nature , they are dangerous to humans if provoked and handled , because their venom contains tetrodotoxin , a neurotoxin powerful enough to kill humans .