Interference of free fatty acids from the hepatopancreas of mussels with the mouse bioassay for shellfish toxins.

Determination of free fatty acids (FFA) in hepatopancreas of mussel, Mytilus coruscus, contaminated by diarrhetic shellfish poisoning (DSP) toxins, was carried out by high-performance liquid chromatography-fluorometry as their 9-anthryldiazomethane derivatives. The FFA in the hepatopancreas of mussels during May 30-June 14 were 443-666 micrograms/g. A marked increase in FFA content was observed on June 20 (2197 micrograms/g hepatopancreas) and June 27 (6322 micrograms/g hepatopancreas). The proportion of polyunsaturated fatty acids (PUFA), including 20:4n-6, 20:5n-3, and 22:6n-3, in mussel FFA increased during the experimental period. Diatoms almost completely dominated the phytoplankton community at the experimental site, suggesting that diatoms were the origin of the PUFA accumulated in mussels. The toxicity of FFA in mussel hepatopancreas on June 27 was sufficiently high as to interfere with the mouse bioassay by injection of an extract of shellfish, the official method for DSP toxin analysis.