Even regarding octopuses, the old adage holds true: if it’s found in Australia, it can probably kill you. Specifically, the blue-ringed octopus packs enough venom in its bite to take down a person in minutes. What is the dastardly appearance of such a deadly creature? A tiny animal no more than 4 inches long, with a pale, yellow coloring and iridescent rings of blue.
The major component of their defensive venom is a chemical known as tetrodotoxin, also found in some fish, amphibians, and shellfish. Tetrodotoxin binds to certain voltage-gated sodium channels, inhibiting their function. Because the action potentials of the nervous system are themselves generated and propagated by the movement of these ions, this is an extremely potent neurotoxin. Its victims may experience paralysis, nausea, numbness, and convulsions until the respiratory system completely shuts down. And if that isn’t bad enough, their saliva delivers it along with histamine, octopamine, hyaluronidase, and a slew of other fun chemicals to make an encounter with this octopus particularly memorable.
While the blue-ringed beauties are the only octopuses with a bite lethal to humans, all come with a venom in their saliva, though it is mainly used for predatory purposes, and you may have noticed evidence of this yourself. If you walk down a beach and notice a shell with a neat hole in it, that is likely due to the radula, or rasping tongue, of a mollusk, octopuses being included in that group. They then spit their venom into the prey to paralyze it, allowing them to enjoy an easy meal. If this is all a little too unnerving, it may be worth noting that they confine the use of this lethal power to hunting and defense-- they will not likely attack a human unprovoked. So, all octopuses have a certain amount of dark alchemy within them, but assuming you aren’t a crab, you don’t have much to worry about from the curious, squishy aliens of the deep.