Accumulation, elimination and biotransformation of paralytic shellfish toxins in ark shell Anadara kagoshimensis

Paralytic shellfish toxins (PSTs) produced by marine dinoflagellates can accumulate in filter-feeding bivalves, causing severe human intoxication. The accumulation, biotransformation and elimination of PSTs in bivalves have a strong influence on their toxicity. The ark shell Anadara kagoshimensis is an important commercial shellfish in China. Field investigations have occasionally found ark shells to be heavily contaminated by PSTs. To understand the biokinetics of PSTs in ark shells, live individuals were fed with toxic dinoflagellate Gymnodinium catenatum (strain MEL11) to determine the accumulation, elimination, and biotransformation of PSTs. An in vitro incubation experiment was also carried out by mixing PST extracts with tissue homogenates of ark shells to examine the biotransformation of PSTs. It was found that toxin accumulation rate in ark shells exposed to toxic algae was very low, which couldn't account for the high toxicity previously found in field investigations. It is highly possible that ark shells can accumulate toxins through other approaches, such as the ingestion of toxic resting cysts. Though the hypothesis is not tested in this study and still requires further investigation, it highlights the importance of searching for more PST sources than the vegetative algal cells. The enzymatic hydrolysis of GC toxins and the reduction of R1-OH PST components were identified as two major biotransformation pathways in ark shells. The hydrolysis of N-sulfocarbamoyl toxins to carbamoyl toxins previously reported in ark shells was not detected in this study.