DINOFLAGELLATE ALEXANDRIUM-TAMARENSE AS THE SOURCE OF PARALYTIC SHELLFISH POISON (PSP) CONTAINED IN BIVALVES FROM HIROSHIMA BAY, HIROSHIMA PREFECTURE, JAPAN

In April 1993, a phytoplankton dinoflagellate was isolated from Hirosh ima Bay, Hiroshima Prefecture, Japan, and unambiguously identified as Alexandrium tamarense on the basis of the morphological characteristic s. The dinoflagellates, cultured in modified SW-2 medium at 15 degrees C for 15 days, showed a specific toxicity of 30.7 x 10(-6) MU/cell. H PLC analysis demonstrated that the toxin was composed mainly of gonyau toxin-4 (GTX4) and protogonyautoxin-2 (PX2 or GTX8) (27.6 and 37.0 mol e%, respectively). Total toxin concentration of this strain was 39.5 f mole/cell. Short-necked clams, mussels, and oysters contaminated by th e dinoflagellate showed a more complicated composition, with GTX1 as t he major component (61.8 mole% for short-necked clams, 60.5 mole% for mussels, 42.5 mole% for oysters), and PX2 was only present in trace am ounts.