Blue-ringed Octopus

  The blue-ringed octopus is one of three or four species of octopus that live in tidal pools in the Pacific Ocean, from Japan to Australia. They are currently recognized as one of the world's most venomous animals. They are quite small and docile, however when agitated or threatened, they will show a display of distinctive blue rings, hence their name. Generally, they hunt small crabs, shrimp as well as small fish if possible.
  They will pounce on their prey, paralyze them with venom and use their beaks to tear off pieces. They then suck out the flesh from a crustacean exoskeleton if necessary.
  The blue-ringed octopus is 12-20 centimeters or 5-8 inches but has a venom powerful enough to kill humans. There is no available antivenom. The venom of the octopus contains tetrodotoxin, 5-hydroxytryptamine, hyaluronidase, tyramine, histamine, tryptamine, octopamine, taurine, acetylcholine, and dopamine. The main component is tetrodoxin, a toxin 10,000 more poisonous than cyanide.