The toxic effect of the dinoflagellate Prorocentrum lima on juvenile American whiteleg shrimp Litopenaeus vannamei and giant lion-paw scallop Nodipecten subnodosus was evaluated. Organisms were exposed to three densities (500, 2000, or 5000 cells mL-1), superoxide dismutase activity and soluble protein in the hepatopancreas and muscle were determined at 1, 6, 24 and 48 h after challenge. Shrimp exposed at 5000 cells mL-1 significantly increased SOD activity in the hepatopancreas at 1 h post-challenge, whereas
enzymatic activity in muscle significantly increased at 24 h at all densities. Scallops exposed to 500 and 2000 cells mL-1 showed significant SOD activity increase in hepatopancreas at 24 and 12 h, respectively. Mortality at 48 h was 100% in scallops exposed to 5000 cells mL-1. Shrimp showed higher levels of SOD activity than scallops. Soluble protein content in the shrimp hepatopancreas was significantly higher at
densities of 500 and 2000 cells mL-1 at 6 and 1 h, respectively. Soluble protein content in the scallop hepatopancreas was higher than control values at 1 h after challenge. In this study, 500 cells mL-1 was enough to trigger SOD activity in two benthic species exposed to the toxic dinoflagellate P. lima
