A review of: Noguchi, T., Arakawa, O. and Takatani, T. 2006. Toxicity of pufferfish Takifugu rubripes cultured in netcages at sea or aquaria on land. Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 1(1), 153-157.
Marine pufferfish of the family Tetraodontidae can be known to possess a neurotoxin (TTX/Tetrodotoxin). This toxin is poisonous to humans, causing paralysis and even death. In Japan ‘Fugu’ is a popular dish which is made from these pufferfish. Many believe the liver to be the tastiest part, however this is also the most toxic. Safe preparation of this dish requires a great amount of training and the serving within restaurants is strictly controlled. The serving of the liver has even been banned due to a frequent occurrence of food poisonings. No detailed studies have been made on the mechanisms of uptake, accumulation, metabolism and excretion of TTX in pufferfish. While they do have a TTX-secreting gland or cells within their skin which is thought to be a defence mechanism, only a small amount if any is ever produced and this does not intoxicate the liver. Previous studies have suggested that the pufferfish do not synthesise the TTX by themselves. Instead they are thought to accumulate it through the food chain. So this study hypothesised that non-toxic pufferfish should be able to be produced if cultured with a TTX-free diet.
Over 5000 species of the pufferfish, Takifugu rubripes were cultured by netcages at sea, and aquaria on land for up to three years. As they are known to accumulate the toxin mainly in the liver and ovary following ingestion, the liver was focussed on for testing, but other parts were also used. Toxicity was assessed using the Japanese official mouse assay method for TTX and also LC/MS analysis. Each tissue was extracted with 0.1% acetic acid and then examined for toxicity through intraperitoneal injection into male mice.
The results indicated that all parts of all pufferfish tested were considered to be ‘non-toxic’ in both the mouse assay where levels were less than 2MU/g and the LC/MS analysis where levels were less than 0.1MU/g. The expression MU is used where 1 MU is defined as the amount of toxin required to kill a mouse in 30 minutes after injection. Anything less than 10MU/g is considered to be non-toxic in food hygiene. This provides solid evidence that the pufferfish become intoxicated through the food chain and non-toxic fish can be successfully produced by netcage or land culture irrespective of culture area and season. If cultured in this way, the fish and in particular the liver can be considered safe to consume.
Marine pufferfish of the family Tetraodontidae can be known to possess a neurotoxin (TTX/Tetrodotoxin). This toxin is poisonous to humans, causing paralysis and even death. In Japan ‘Fugu’ is a popular dish which is made from these pufferfish. Many believe the liver to be the tastiest part, however this is also the most toxic. Safe preparation of this dish requires a great amount of training and the serving within restaurants is strictly controlled. The serving of the liver has even been banned due to a frequent occurrence of food poisonings. No detailed studies have been made on the mechanisms of uptake, accumulation, metabolism and excretion of TTX in pufferfish. While they do have a TTX-secreting gland or cells within their skin which is thought to be a defence mechanism, only a small amount if any is ever produced and this does not intoxicate the liver. Previous studies have suggested that the pufferfish do not synthesise the TTX by themselves. Instead they are thought to accumulate it through the food chain. So this study hypothesised that non-toxic pufferfish should be able to be produced if cultured with a TTX-free diet.
Over 5000 species of the pufferfish, Takifugu rubripes were cultured by netcages at sea, and aquaria on land for up to three years. As they are known to accumulate the toxin mainly in the liver and ovary following ingestion, the liver was focussed on for testing, but other parts were also used. Toxicity was assessed using the Japanese official mouse assay method for TTX and also LC/MS analysis. Each tissue was extracted with 0.1% acetic acid and then examined for toxicity through intraperitoneal injection into male mice.
The results indicated that all parts of all pufferfish tested were considered to be ‘non-toxic’ in both the mouse assay where levels were less than 2MU/g and the LC/MS analysis where levels were less than 0.1MU/g. The expression MU is used where 1 MU is defined as the amount of toxin required to kill a mouse in 30 minutes after injection. Anything less than 10MU/g is considered to be non-toxic in food hygiene. This provides solid evidence that the pufferfish become intoxicated through the food chain and non-toxic fish can be successfully produced by netcage or land culture irrespective of culture area and season. If cultured in this way, the fish and in particular the liver can be considered safe to consume.
8 comments:
Ah yeah, I remember this, but sales have not taken off for non toxic fish, because it removes the thrill
An interesting review. Perhaps this is further evidence that TTX is rarely produced by the puffer fish but is the result of microbial colonisation.
Hi Samantha.
This is a really interesting post - I wonder if this change in diet will effect its taste!
I hope you're having a good holiday
Ye. Why would you want to eat puffer fish if there wasn't the risk of you being fatally poisons, that's just no fun at all!
On a more serious note this is a very interesting paper, I'd read in various places about these puffer fish being bred and reared without producing the toxin and it was nice to finally see this information in a journal. Thanks for the review and the reference to the journal, both were a good read.
Hello eager commenters! Getting them in before midnight? I don't think my response will make it.
Corin - Yep that does seem to be the case! People claimed how the liver is the tastiest bit and now the risk of death is gone, its not so exciting! Crazy.
Rachelle - Yep, i think you're right. This definitely provides further evidence that TTX in pufferfish is down to the toxin travelling up the food chain rather that by its own synthesis.
Theo - That's a really interesting though actually! As Corin said, it seems to have put people off as the excitement was all about the risk. But maybe that isn't the only reason... maybe it does taste different? Hmm... I hope you're having a lovely holiday too! :)
Matt - It is pretty ridiculous. Intriguing people...?
Thanks for the appreciation! I'd read a little about it before too but hadn't realised that the change in diet caused the lack of intoxication. Quite an interesting topic!
P.S. Dear Colin... The above response should definitely count as 4 comments as its 4 replies :D Ha.
It's good to see you so awake after midnight!
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