A blue ringed octopus - they're a cute looking tiny octopus but quite capable of killing a human.
What's worst is that after getting bitten by one you will be mentally alert but completely unable to do anything as you feel your body just stop doing things that keep you alive (like breathing)...
as you feel your body just stop doing things that keep you alive (like breathing)...
As I understand it (and to be fair, I'm no octopus scientist or human medical doctor) it's pretty much just breathing that's the issue. It doesn't really directly cause any damage on its own (though the consequences of not breathing can and will of course cause quite a lot of damage in pretty short order)
The venom causes paralysis, basically by (someone correct me if I'm wrong) clogging up the receptors your body uses to send signals to your muscles. It will all get cleared up in about 24 hours or so though.
Problem is that you use some of those muscles to breathe. But if you make it to shore (you also need some of those muscles to swim) and if you get put on a ventilator right away (to do the breathing for you,) your prognosis is actually pretty good and there's a nearly 100% survival rate (although that has to be two of the biggest "ifs" in all of medicine)
Another thing that comes to mind is your heart also uses muscles to do its thing, and I'm not totally clear on why that doesn't seem to be a factor here, since paralyzing those muscles is basically just instant cardiac arrest. I did a bit of googling, but I'll be honest I was in deep over my head in medical jargon and couldn't make heads nor tails of it. I think my takeaway is that tetrodotoxincan affect the heart muscles, but I guess for whatever reason (dosage? Different kinds of muscles? The way your body processes the venom and moves it around your body? I really don't know) it just kind of doesn't, which I guess is lucky for us. I'm kind of hoping someone who speak doctor will maybe see this and give an ELI5 answer to that.
I suspect there's probably a lot of minor consequences, like I bet your next trip to the bathroom once you recover in going to be some sort of event after your bowels stopped moving for 24 hours, but otherwise it seems like if you hang out on a ventilator for a day unable to move (which, to be fair, is probably one of the last ways I'd want to spend a day, but I guess it narrowly beats out a refrigerated cubby in the morgue) you're pretty much in the clear to get on with your life.
An anaesthesist friend of mine once told me that there are two kinds of muscles - the ones you can actively control (such as muscles in arms and legs and also the muscles for breathing) and those you cannot, such as your heart and intestine-muscles (around the gut etc.). The latter has a different kind of receptors and isn’t affected by the stuff that they use in hospitals to put you down, but since the breathing is stopped, you’ll always be intubated.
I guess this poison is of the same kind but I don’t know the technicalities…
To explain it in simple terms, your heart doesn't get its beating signal from the brain, the sinus node takes care of that and is located in the heart. What the brain (and other parts of your body) does is tell the heart to beat faster or slower when required. So the kind of paralysis caused by the octopus doesn't affect your heart because it doesn't need to use any external pathways to send the signal to the muscle to contract.