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prymnesin

n. (context organic compound English) Any of a class of phycotoxins made by the alga (taxlink Prymnesium parvum species noshow=1), also toxic to fish.

Wikipedia
Prymnesin

Prymnesin is a chemical with the molecular formula .

Prymnesins are a class of phycotoxins made by the alga Prymnesium parvum. It is known to be toxic to fish, causing mass fish deaths around the world, including in Texas and England.