Production of tetrodotoxin in puffer fish embryos.

It has been accepted that puffer fish accumulates tetrodotoxin through the food chain. This indicates that tetrodotoxin in puffer fish is exogenous. The present study, however, describes an endogenous origin of tetrodotoxin in puffer fish. For this purpose, the ovulated oocytes from puffer fish Fugu niphobles were artificially fertilized and cultivated. The toxin levels of embryos increased gradually with development until the time of hatching, suggesting that the increased toxin is a product of embryos.