Rights: University of Waikato. All Rights Reserved. Published 4 September 2012 Download

Paul McNabb and Dr Susie Wood of the Cawthron Institute in Nelson discuss the toxin tetrodotoxin. Paul explains the effects of tetrodotoxin on the human body and talks about just how poisonous it is. Susie explores where tetrodotoxin might be found and how its origins and reasons for existing are still a mystery.

Jargon alert: Natural toxin – some scientists refer to toxins produced by living organisms as natural toxins or biotoxins.


Tetrodotoxin, which we abbreviate as TTX, is an organic molecule. It’s highly poisonous and it’s a chemical that binds to sodium channels, and that’s a key part of the nerve function. They stop the flow of sodium ions into cells, which is how nerves communicate through a body, and so that’s why they’re very, very toxic. They stop nerves from working, and it shuts down a nervous system, stops things like breathing and muscular function including heart function.

Tetrodotoxin does represent a real threat to humans. We know that between 1 and 2 milligrams of tetrodotoxin is enough to kill a person, and that’s a relatively small amount. So in order to visualise it, it would be roughly one grain of sugar. So if you had that one grain and it was all tetrodotoxin, then that would be enough to kill a person. And because we’ve been able to study these slugs relatively intensely, we know that per gram of slug there can be up to a milligram of tetrodotoxin in every gram, and the slug can be 10 grams in weight. So there’s approximately 10 milligrams in a slug, and obviously that’s more than enough to kill a person. So it is a real risk if, particularly if people were eating slugs.

Tetrodotoxin – it’s a natural toxin, a neurotoxin. It’s produced by a really wide range of marine organisms. We find it on marine and terrestrial organisms, so we find it in octopus, we find it in lizards, frogs, and most recently we’ve found it in slugs.

One of the great mysteries I guess in the marine science or the marine natural toxins is where is TTX produced and what is it produced for? There’s lots of speculation about why marine organisms and terrestrial organisms might produce TTX. One of the main ones is that the organisms produce it as a defence mechanism to stop predators eating them and particularly for protection of their young.

Auckland Regional Public Health Service
Jarrod Walker
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