[The toxification of juvenile cultured kusafugu Takifugu niphobles by oral administration of crystalline tetrodotoxin].

Non-toxic cultured juvenile kusafugu were fed with diet containing crystalline tetrodotoxin (TTX) for 30 days and then fed with non-toxic diet for 170 days. During this period, 5 fish were sampled and the toxicity of each tissue was determined periodically. The amount of total accumulated toxin in the fish was 90 microg, representing 50% of the administered TTX (180 microg/fish) at the 60th day. It decreased to 54 microg (30%) at the 80th day and then remained unchanged up to the 200th day. The amount of toxin in the liver amounted to 40 microg (45% of total accumulated toxin) at the 30th day and gradually decreased to 5 microg (10%) at the 200th day. The toxin amount in the skin reached the highest level with 30 microg (30%) at the 50th day and then remained unchanged during the experimental period. The testes had almost no toxicity. Although the ovaries were immature, the toxin amounts increased as the weight of the tissues increased. With administration of crystalline TTX, all kusafugu used in the experiment became toxic and retained the toxin at the level of 30% of the administered toxin for about 5 months thereafter, while being fed with non-toxic diet.