Influence of initial toxicity and extraction procedure on paralytic toxin changes in the mussel.

Farmed mussels were artificially contaminated with a pure culture of an Alexandrium tamarense toxic strain (MOG 835), to assess the effect of initial toxicity on paralytic toxin change during the depuration process. As previously observed in mussel, gonyautoxin GTX2 is eliminated more slowly than other gonyautoxins. A toxic level (1300 micrograms PSP per 100 g meat) is required to produce a drastic change in the depuration course, i.e. a 'fast' depuration rate followed by a 'slow' one. Below this threshold, decontamination becomes slower as the proportion of GTX2 increases over the time course. Although GTX2 is slowly eliminated during the depuration process, it is also formed in increasing quantities during the contamination phase. It remains to be determined whether changes in GTX2/GTX3 ratios are due to chemical or biological transformation.