Superoxide dismutase activity in juvenile Litopenaeus vannamei and Nodipecten subnodosus exposed to the toxic dinoflagellate Prorocentrum lima

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.