Forget Sharks – What We Really Need to Fear is Flatworms!

Just when you thought it was safe to go looking for fishing bait … researchers have found the deadly neurotoxin tetrodotoxin in two species of flatworms – the first time it’s been discovered in creatures that live totally out of the water.

Tetrodotoxin (TTX) gets its name from Tetraodontiformes, the order of ray-finned fish that includes pufferfish, porcupinefish, ocean sunfish and triggerfish which are known to carry the paralysis-inducing toxin. It’s also found in the blue-ringed octopus, rough-skinned newt and moon snail but has never been seen in terrestrial invertebrates ... until now.

Researchers at California State University, Bakersfield, confirmed the presence of tetrodotoxin in two species of terrestrial flatworm - Bipalium adventitium and Bipalium kewense. The concentration was high enough to paralyze the large earthworms that these flatworms feed on. It was also found in egg capsules, suggesting that this is a defense mechanism to protect them until hatching.

TTX is about 100 times more poisonous than potassium cyanide. Symptoms in humans typically develop within 30 minutes of ingestion and death occurs in 4 to 6 hours, but not before the victim suffers from things like paralysis, seizures, respiratory failure, coma, severe abdominal pain, complete respiratory failure and cardiovascular collapse. There’s no known antidote but victims can eventually recover if they survive the symptoms.

The source of the poison in the worms is a mystery, according to the study published in the open access journal PLOS ONE by Amber Stokes, a researcher at CSUB. Pufferfish may accumulate it by eating bacteria that produce TTC and the blue-ringed octopus has similar bacteria already in its system, but this isn’t the case with flatworms.

Are you scared yet? Both are native to Asia but have been found in North America and are considered invasive species. The study concludes with this observation:

Our findings provide a potential avenue for TTX to move up the food chain in terrestrial organisms.

Please don’t eat the flatworms!