The blue-ringed octopus is one of the most venomous animals in the ocean, capable of delivering a neurotoxin powerful enough to cause rapid paralysis in humans. Its venom, tetrodotoxin, blocks nerve ...

Octopuses have gotten a reputation for being cunning camouflagers and intelligent creatures. But some are known for a more ominous reason: They're deadly. One group — the blue-ringed octopus (genus ...