Blue-ringed octopus

The octopus produces venom containing tetrodotoxin, histamine, tryptamine, octopamine, taurine, acetylcholine and dopamine. The venom can result in nausea, respiratory arrest, heart failure, severe and sometimes total paralysis, blindness, and can lead to death within 90 minutes if not treated.
 
 size—12 to 20 cm (5 to 8 in)