Wiktionary
yessotoxin
n. (context organic compound English) A toxin, produced by some dinoflagellates, that can accumulate in mollusks and subsequently cause food poisoning in humans.
Wikipedia
Yessotoxin
Yessotoxins are a group of lipophilic, sulfur bearing polyether toxins that are related to ciguatoxins. They are produced by a variety of dinoflagellates, most notably Lingulodinium polyedrum and Gonyaulax spinifera.
When the environmental conditions encourage the growth of YTX producing dinoflagellates, the toxin(s) bioaccumulate in edible tissues of bivalve molluscs, including mussels, scallops, and clams, thus allowing entry of YTX into the food chain.