Paralytic shellfish toxins in tropical oceans

The tropics possess some of the world's richest marine environments, most notably coral reefs. Concealed within these ecosystems are a group of potent neurotoxins called the paralytic shellfish toxins ( PSTs), the most famous of which is saxitoxin. Thirty years ago, PSTs were recognized as a major danger to seafood consumers in the tropics. The tropical dinoflagellate Pyrodinium bahamense biosynthesizes PSTs and its contamination of seafood has caused more illnesses and deaths than any other PST-producing microalga. Apart from this and other dinoflagellates, PSTs have been confirmed in tropical benthic algae, molluscs, echinoderms, crustacea, and other arthropods. Some of these organisms are unique in that, to date, they have only been found to be toxic in tropical oceans. For example, species of grazing and predatory gastropods, crabs, and more recently cephalopods have been discovered to contain PSTs in a number of intertidal tropical locations. These animals are thought to accumulate the toxins from benthic sources rather than toxic dinoflagellates as happens with filter-feeding bivalve molluscs such as clams and oysters. Here we evaluate the current understanding of PST transmission through tropical food webs. Finally, we consider the prevalence of PST intoxications in tropical regions and their social and economic costs.