Ichtyotoxic activity of extracts from Mexican marine macroalgae

Seventy-three species of macroalgae from the Mexican Pacific, Atlantic and Caribbean coast were screened for ichtyotoxic activity. Ethanolic, acetonic and aqueous extracts were prepared and tested against the fish Carassius a uratus. The extracts were classified on the basis of their effects as: toxi c if the fish died in two hours or less; moderately toxic, if the organism behaved abnormally but death did not occur, and non-toxic if the fish did n ot display any change. 79% species were ichtyotoxic to some degree. Extract s of 39 species were toxic, with at least one extract with lethal effects, 19 were moderately toxic and 15 species were non-toxic. Only the extracts o f Dictyota bartayresiana, Dictyota cervicornis, Lobophora variegata, Bryoth amnion triquetrum and Laurencia obtusa were toxic in all three solvents. Th e acetone and ethanol extracts were more active, and therefore are more sui table for extraction of toxic substances.