The Wonderfully Tasty, and Deadly, Fugu

One of the more, uh, interesting culinary experiences I have had in Asia was ordering fugu (pufferfish) sushi at a Japanese restaurant in China. A few moments after my order, a plate was sat in front of me that contained lots of fresh, white sushi slices...positioned just below the still-gasping decapitated fugu head. My dad was so disturbed that he asked the waitress to take the fugu head away while I happily chomped away at the delicious sushi. Well, at least I knew it was fresh!

The fugu, or pufferfish, is a delicacy in Asia (and particularly Japan) due to the dangers inherent in consuming it. Fugu liver and ovaries, and the flesh to a much lesser degree, contain a potent neurotoxin called tetrodotoxin. For this reason, sushi chefs in Japan must be specially trained and licensed to prepare fugu for consumption, with only 30% passing an extremely rigorous test (go here for a video of the test).

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Consuming fugu in Japan is relatively safe, however there are still dozens of deaths per year related to tetrodotoxin poisoning from fugu. The proper preparation of fugu is shown in the video below.

Tetrodotoxin (TTX) is a sodium channel blocker with no antidote, although several Japanese biotech companies are working on one. It binds to the pores of the voltage-gated, fast sodium channels in nerve cell membranes. TTX is not unique to fugu--it is also found in some newts, parrotfish, toads, several starfish, an angelfish, etc. The first recorded incident of fugu poisoning was from Captain Cook's log in the 1770s. His men caught and ate several 'spiny tropical fish' and fed the leftovers to the pigs kept on board. While the crew who ate the fugu felt ill and weak, all the pigs died, suggesting that the crew received a mild dose of TTX while the pigs ate the livers and ovaries and received a lethal dose.

Those poisoned gradually lose muscle control, although not consciousness, and eventually suffocate to death when the diaphragm becomes paralyzed. However, in very small amounts, approximately the amount found in fugu sushi, TTX gives a funny tingly sensation on the tongue and lips. Interestingly, the fugu itself is not affected by the toxin due to a mutation in the protein sequence of the sodium channel pump on its nerve cell membranes, and there is a Fugu Genome Project (Sydney Brenner's idea). The source of the fugu's TTX is hypothesized to be a bacteria called Psuedoalteromonas tetraodonia.


Just last month, a handful of deaths due to fugu poisoning occurred in Thailand when some unscrupulous fishmongers sold fugu as salmon. I actually saw a very large fugu, which was slow-moving but very wary of people, when I was snorkeling in Malaysia in June. And what does it feel like to be poisoned by fugu? A firsthand account describes it thusly:

Approximately four hours had passed after the fugu meal - I was not the only person who felt numb on finger tips. "Probably we ate poison today," someone said. "My finger tips won't hold a piece of mah-jong ," someone else joined. We all felt something out of ordinary but nobody took the matter seriously.

The mah-jong was over and I tried to rise for the guest's belongings upstairs. I fell on my hip before I knew. "What on earth is the matter?" I wondered, but managed, while feeling ny body numb, to go upstairs and get back to my guests.

"I feel dizzy, " someone said. "Something is strange, " others uttered and they all left. I felt too sick to put things away. "Sorry but let me go to bed," I excused myself and rose to go to my bedroom upstairs, then I suddenly felt like vomiting. My stomach by then was empty and left me in sheer agony. I felt dizzy and crawled on all fours to the bed...

I felt my whole sickening rotation whether I opened or closed my eyes. I felt pressures on the breast and hard to breathe....

I remember joking under all such agonies, "If I should die, take 48 hours before you bury me. You may come to life again when poisoned by fugu."

My poisoned sickness lasted for good three days and nights. The Doctor came for camphor injections and said that I would have to wait for natural recovery. After all, none of us died or appeared in the newspapers.

TTX also has a scientific use-- it has been used in neural and tissue preparations to block certain types of sodium channels while leaving others (those resistant to TTX, such as cardiac tissue) unhampered. This allowed a scientist to measure and isolate certain populations of sodium channels.

Fore more info, as well as an example of a dinner of fugu, check out this podcast on fugu by National Geographic.


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Okay the image of the faceless, gasping pufferfish being disemboweled is going to stick in my mind forever.

I'm not a vegitarian, but cutting up live animals crosses some line with me.

Every time I have the urge to eat fugu, I just go to the dentist, get a cavity filled, and then I hit McDonald's for a Filet-o-Fish before the Novocain wears off.

That was a very interesting and well written piece.
Fortunately for me, I dislike fish in general and the idea of eating raw fish sickens me in particular. Eating raw toxic fish is not my idea of a fun risk-taking adventure. I'd rather dive out of airplanes.....
Or listen to Rush Limbaugh....

For this reason, sushi chefs in Japan must be specially trained and licensed to prepare fugu for consumption, with only 30% passing an extremely rigorous test.
Consuming fugu in Japan is relatively safe, however there are still dozens of deaths per year related to tetrodotoxin poisoning from fugu.

But you didn't try it in Japan. You said you were in China, whose record of consumer protection is, well, a recent topic of headlines. BTW, did you survive?

By Tegumai Bopsul… (not verified) on 25 Sep 2007 #permalink

Tegumai: I actually didn't know at the time that I was eating fugu, and that it was dangerous to do so. It wasn't until later that someone pointed out that that was what I ate that I got curious about the toxin and the fish. I didn't even get the tingly sensation. :/ It was delicious though mild in flavor.

Abbie, sorry for the traumatic image, although I thought the video did a nice job in illustrating the expertise and skill involved in preparing fugu. I might point out that when anyone catches fish they are usually beheaded and gutted on the spot. The wriggling taking place post-decapitation is merely reflex, if that makes you feel any better.

Fish toxins are a fascinating topic. When discussing tetrodotoxin, one should also bring up ciguatoxin (CTX) which is interesting as it acts completely opposite of TTX by increasing Na+ permeability [ PDF link to research paper]. In fact, TTX blocks the action of ciguatoxin -- though I probably won't recommend anybody try using TTX as an antidote for CTX poisoning.

I'm not sure if anyone has looked at the reverse of this and if CTX or a variant might be useful in the treatment of TTX poisoning. The chemical they were looking at, 4-aminopyridine (4-AP), is a potassium channel blocker, which can restore breathing but also cause a whole host of other (potentially fatal) problems.

I might point out that when anyone catches fish they are usually beheaded and gutted on the spot.

That's a pretty severe penalty. Wouldn't a few days jail time be adequate?

By Tegumai Bopsul… (not verified) on 25 Sep 2007 #permalink

Fascinating topic. Ages ago there was an episode of the Simpsons where Homer mistakenly eats an incorrectly prepared Fugu. I remember watching it, and then running of to the library (I believe it must have been on TV before the age of the internet...) to read more about it.

By Uschi Symmons (not verified) on 25 Sep 2007 #permalink

Another interesting thing about fugu is that it has an unusually small genome, with tiny introns. This caught the interest of Sydney Brenner, who initiated the Fugu genome project, hypothesizing that it would be easier to identify functionally important regions in a genome with little if any "junk."

Very interesting. I'm a big fan of sushi myself, but it will take some convincing ($$$) for me to try fugu.

I didn't watch the chef training video yet; but I hope part of their exam involves them having to eat their own fugu dish :D

I can't stand fish either. However, I now wonder whether anyone has thought to joke that the name comes from the numb-mouthed response of an American tourist to discovering that he'd been served something poisonous. :D