2017 Volume 83 Issue 4 Pages 589-598
The causative dinoflagellate blooms of paralytic shellfish toxins (PSTs) and changes in the toxin contents and the profiles in both arc shell Scapharca broughtonii and Japanese cockle Fulvia mutica in Osaka Bay for three years from 2013 to 2015 were investigated. During the investigation, the toxic dinoflagellate Alexandrium tamarense and A. catenella occurred in Osaka Bay. A. tamarense was the most important causative species in contamination of bivalves with PSTs. Contamination and detoxification in arc shell with PSTs were slower than those in Japanese cockle and slight amounts of PSTs remained in the arc shell throughout the year. On the other hand, PSTs in Japanese cockle were not detected after the end of bloom of A. tamarense. The dominant toxins of arc shell were GTX2 and GTX3 and relative ratio of STX in the arc shell increased with decontamination of toxins. In contrast, the dominant toxins in Japanese cockle were C1 and C2. In conclusion, the rate of GTX1 and GTX4 increased during the bloom of A. tamarense in both species. It was suggested that toxins in Japanese cockle were rapidly excreted without any in vivo conversions of toxins from the causative dinoflagellates.