Tetrodotoxin 101

A good way to hook students into the wonderful world of toxicology is tetrodotoxin. Sound familiar? It’s what makes fugu, or puffer fish, what it is - a potentially deadly Japanese delicacy. Or does it? Would the delicacy be so appealing if the consumer didn't risk death or paralysis?

For those unfamiliar with fugu or tetrodotoxin, note that a mere “taste” of the stuff can and does kill. Although not the most potent toxin in the toolbox (recall that we’re talking toxin - or naturally produced poison) that honor most likely goes to either C. botulinum toxin (the toxin whose presence may be indicated by those puffed up cans – like the tuna can I once pulled from a grocery shelf,) or ricin – most recently of Las Vegas fame – and produced by the lowly castor bean.

Although non-toxic preparation of fugu has been raised to an art by highly skilled Japanese chefs, and although not all wild puffer fish contain enough toxin to kill, one article estimates that upwards of 50 mortalities may occur each year in Japan following puffer fish ingestion.

But now there’s good news for those who just must nibble – yet who’d prefer to avoid death or illness (tetrodotoxin inhibits muscle contraction causing paralysis). A recent article in the New York Times by Norimitsu Onishi reveals not only some interesting fugu history, but also describes the current trend towards raising tetrodotoxin free fugu.

For years, scientists seeking out the source of fugu (and many other marine species) tetrodotoxin had been baffled – where did it come from? Was it produced by the fish themselves or was it in the food they ate? And why didn’t it kill puffer fish and other tetrodotoxin laden marine animals?

Recent studies now suggest that, like many other potent toxins, tetrodotoxin is produced by the smallest of small, bacteria. By providing a home for bacteria, the boxy puffer is offered protection (and fortunately for the puffer fish, they’re at an advantage thanks to a genetic mutation, which makes them immune to its toxicity.)

As you might guess, here’s where the non-toxic fugu come in. By knowing the source, fish farmers can now feed fugu tetrodotoxin-free food (say that ten times fast) producing a risk free meal.

Although, for some the thrill of fugu may be in the risk – for others writes Onishi,, fugu liver is just plain tasty – like foie gras but without the guilt.