DSP toxin contents in Dinophysis fortii and scallops collected at Mutsu Bay, Japan

Cell densities of toxic phytoplankton species responsible for diarrhetic shellfish poisoning (DSP) were monitored at a sampling site in Mutsu Bay, Japan, in 1995. Dinophysis fortii almost completely dominated the toxic phytoplankton community. Okadaic acid (OA) and dinophysistoxin-1 (DTX1) contents in both D. fortii cells and midgut glands of scallops collected at the same sampling site were determined by HPLC - fluorometry. DTX1 was detected from D. fortii and scallops. The contents of DTX1 in D. fortii changed markedly during the experimental periods (5-252 pg cell(-1)). The highest concentration of DTX1 in the midgut glands of scallops coincided with the period of relatively high cell densities of D. fortii with the highest content of DTX1 (252 pg cell(-1)). The results demonstrate that toxin content in the cells is an important factor affecting the toxicity of shellfish.