Tetrodotoxin is a bacteria-derived organic molecule assimilated into the tissues of the pufferfish or into the modified salivary glands of the blue-ringed octopus. The primary toxin from the blue-ringed octopus, maculotoxin, was determined to be in fact tetrodotoxin, the first instance of tetrodotoxin being identified as a venom component. Envenomation causes acute respiratory failure through paralysis of the respiratory musculature due to tetrodotoxin being a highly specific Na+ channel blocker in excitable tissues. This affects only the nerves of the voluntary muscles such as eyelids or lungs, leaving the involuntary muscles such as cardiac unaffected.