Comparative analysis of paralytic shellfish toxin content and profile produced by dinoflagellate Gymnodinium catenatum isolated from Inokushi Bay, Japan

Paralytic shellfish toxin contents and profiles were investigated using shellfish toxin-producing dinoflagellate Gymnodinium catenatum strains isolated from Inokushi Bay during the March and July 2002 outbreak. The March strains, which were 72 strains isolated from bloom water, exhibited average growth rates of 0.25 divisions day ^-1 due to sub-optimal temperature. The average toxin content was 321 f mole cell ^-1. The principal toxin were C1+2 (79.8 mole%) and GTX 5+6 (18.0 mole%), and minor components were characterized as GTX 2+3, dcGTX2+3, and neoSTX+STX. Interestingly, 7 strains were clearly distinguished from those of other strains by the complete presence of GTX1+4. In the July strains, which were 33 strains isolated from bloom water, the average growth rate and toxin content was 0.34 divisions day ^-1 and 160 f mole cell ^-1, respectively. C1+2 (83.3 mole%) and GTX 5+6 (10.6 mole%) were the principal toxins, as in the March strains. However, carbamoyl toxins in the July strains were increasing with decreasing N-sulfocarbamoyl toxins in the Mach strains. We also observed major changes in toxin profile, evident by the increase of C1+2 and the decrease of GTX 5+6 in response to increasing temperature, using a single March strain. Minor components of July strains were characterized by GTX2+3, neoSTX, STX and dcGTX2+3. Thus, if we were to consider the toxin profile percentage based on temperature variation, G. catenatum outbreaks in March and July may have originated from one and the same population.