Marine biotoxins in shellfish – Saxitoxin group

Saxitoxin (STX)-group toxins are a group of closely related tetrahydropurines and have been detected in filter-feeding bivalve molluscs such as oysters, mussels, scallops, and clams from various parts of the world. They are mainly produced by dinoflagellates belonging to the genus Alexandrium: e.g. Alexandrium tamarensis, A. minutum (syn. A. excavata), A. catenella, A. fraterculus, A. fundyense and A. cohorticula. STX-group toxins cause paralytic shellfish poisoning (PSP) in humans, characterised by symptoms varying from a slight tingling sensation or numbness around the lips to fatal respiratory paralysis. In fatal cases respiratory arrest occurs 2 to 12 hours following consumption of shellfish contaminated with STX-group toxins. More than 30 different STX analogues have been identified of which STX, NeoSTX, GTX1 and dc-STX seem to be the most toxic ones.