Toxic effect of the harmful dinoflagellate Cochlodinium polykrikoides on the spotted rose snapper Lutjanus guttatus.

The dinoflagellate Cochlodinium polykrikoides isolated from Bahía de La Paz, Gulf of California, showed an important short-term toxic effect on the spotted rose snapper Lutjanus guttatus. This microalga was able to decrease fish liver catalase activity and lipid peroxidation. Fish exposed to live dinoflagellates developed an abnormal mucus secretion on the gills that was directly related to algal cell concentration. Hepatic catalase inhibition and an increase in mucus secretion on the gills occurred when fish were exposed to 2 x 10(6) cells L(-1) of C. polykrikoides. Lipid peroxidation was significantly different at 4 x 10(6) cells L(-1) and the hepatosomatic index decreased at 3 x 10(6) cells L(-1). Our results suggest that oxidative stress contributes, at least in part, to the ichthyotoxic effect of C. polykrikoides from the Gulf of California.