The Beautiful and Deadly Blue Ringed Octopus

The blue-ringed octopus (genus Hapalochlaena) are three (or perhaps four) octopus species that live in tide pools in the Pacific Ocean, from Japan to Australia. Despite their small size and relatively docile nature, they are currently recognized as one of the world's most venomous animals.http://animal.discovery.com/convergence/oceans-deadliest/deadliest-creatures/deadliest-creatures_05.html They are recognized by their characteristic blue and black rings and yellowish skin. It hunts small crabs, hermit crabs, and shrimp, and may bite attackers, including humans, if provoked or stepped on.

Tetrodotoxin (also known as "tetrodox" and frequently abbreviated as TTX) is a potent neurotoxin with no known antidote. There have been succesful tests of a possible antidote in mice, but further tests must be carried out to determine efficacy in humans.Rivera VR, Poli MA, Bignami GS. Prophylaxis and treatment with a monoclonal antibody of tetrodotoxin poisoning in mice. Toxicon. Sep 1995;33(9):1231-7. Medline. Tetrodotoxin blocks action potentials in nerves by binding to the pores of the voltage-gated, fast sodium channels in nerve cell membranes. The binding site of this toxin is located at the pore opening of the voltage-gated Na+ channel. Its name derives from Tetraodontiformes, the name of the order that includes the pufferfish, porcupinefish, ocean sunfish or mola, and triggerfish, several species of which carry the toxin. Although tetrodotoxin was discovered in these fish and found in several other animals (e.g., Blue-ringed Octopus, Rough-skinned newt, and Naticidae) it is actually the product of certain bacteria such as Pseudoalteromonas tetraodonis, certain species of Pseudomonas and Vibrio, as well as some others.

Its mechanism of action, selective block of the Na channel, was showed definitively in 1964 by Toshio Narahashi and John Moore at Duke University, using Moore's sucrose gap voltage clamp technique.Voltage clamp at Scholarpedia