Features of paralytic shelfish poison occurring in tohoku district.

Abstract

A survey acrried out from the spring to summer of 1979 at 31 stations in Tohoku and nearby areas revealed that shellfishes were infested in varied degrees by paralytic shellfish poison at almost all stations. The rates of accumulation of toxin differed markedly from species to species and the toxicity levels decreased in the following order: scallop Patinopecten yessoensis, scallop Chlamys nipponensis akazara, mussel Mytilus edulis, and oyster Crassostrea gigas. The edible tunicate Holocynthia roretzi also accumulated the toxin at a fairly high level. In the absence of the causative plankton M. edulis eliminated the toxin rapidly but P. yessoensis retained it for a long period at a high level. Protogonyaulax tamarensis was identified as the causative organism occurring during the investigation period. It caused mussels to become highly toxic even at a low population density of several cells per mililiter.