Paralytic Shellfish Poison Infestation to Oyster Crassostrea gigas Due to Dinoflagellate Gymnodinium catenatum in the Amakusa Islands, Kumamoto Prefecture

At the end of January 1998, wild oysters, Crassostrea gigas, in Miyanokawachi Bay, Amakusa Islands, Kumamoto Prefecture were toxified with PSP probably due to Gymnodinium catenatum, whose cell density was 308 cells/mL. The toxicity score of the oysters ranged from 3.0 to 263MU/g of the edible portion. Toxin compositions of the oysters and the dinoflagellate by high performance liquid chromatographic analysis for PSP resembled each other, consisting of C1 (PX1) and C2 (PX2) as the major toxins and, GTX5, GTX6, dcGTX2, dcGTX3 and dcSTX as the minor toxins.From these results, it was concluded that toxic oysters in Miyanokawachi Bay, Amakusa, Kumamoto had been toxified by G. catenatum through the food chain.