The blue-lined octopus (Hapalochlaena fasciata) is one of four species of extremely venomous blue-ringed octopuses. It can be found in Pacific Ocean waters that stretch from Australia to Japan. Along with its other closely related species, the blue-lined octopus is regarded as one of the most dangerous animals in the sea, and its venom can be fatal to humans. They often hide in crevices of reefs, empty seashells, and other ocean resources they can find to conceal their identity. They do not use their venom (known as tetrodotoxin) to kill their prey, but instead trap it inside their arms and pierce them with its parrot-like beak.
Lethality
Blue-lined octopuses can be lethal to humans. Their saliva contain a special neurotoxin called tetrodotoxin. However, the species is more likely to flee and find shelter in an encounter due to their extremely shy nature. It poses most danger to those who pick up the octopus and physically touch it. The male cautiously approaches the larger female, often from behind to reduce the risk of triggering agression. The male bites her aorta, injecting tetrodotoxin (TTX). Within ~8 minutes, she's paralyzed as breathing slows, the body pales, and reflexes vanish, buying him time and safety. While she’s immobilized, the male uses his specialized hectocotylus arm to transfer spermatophores (sperm packets) into the female’s mantle cavity.