Confirmation of yessotoxin production by the dinoflagellate Protoceratium reticulatum in Mutsu Bay

Yessotoxin (YTX) is a shellfish toxin and its contamination in bivalves has seriously damaged shellfish industries. The biogenetic origin of YTX was identified as the dinoflagellate Protoceratium reticulatum (Claparede et Lachmann) Butschli collected in New Zealand and Yamada Bay, Iwate in Japan. Scallops cultured in Mutsu Bay, Japan, were frequently contaminated with YTX, however, occurrence of P. reticulatum in this bay and YTX production by the local strains have not been investigated. Eight strains of P. reticulatum, isolated from the bay, were cultured in the laboratory, and analyzed by fluorometric high-pressure liquid chromatography and liquid chromatography/mass spectrometry methods for YTX production and composition. All strains tested were confirmed to produce YTX, and none of them produced known YTX analogs. Toxin amount and composition differed from strain to strain. This result is also confirmation of one of the biogenetic origins of YTX in Mutsu Bay.