Biomarkers of Oxidative Stress in the Polychaete Eurythoe complanata (Amphinomidae) Under Short Term Copper Exposure

Metal exposure may induce cellular injury due to membrane breakdown, which would affect cellular structures and functions. Metal toxicity is usually related to a redox cycling phenomenon which promotes the formation of free radicals, identified as responsible for oxidative stress. The free radical-mediated effects include DNA damage, enzyme inactivation, and cellular or subcellular membrane peroxidation resulting in the generation of lipid hydroperoxides and complexes of carbonyl compounds including malondialdehyde (MDA) (Di Giulio et al. 1989; Viarengo et al. 1990; Winston et al. 1991). Cellular damage is usually preceded by the impairment of antioxidant biochemical mechanisms that quench radicals before they initiate their molecular effects. Among oxidative defenses, the antioxidant enzymes catalase (CAT, EC. 1.11.1.6), gluthatione peroxidase (GPX, EC. 1.11.1.9), gluthatione reductase (GR, EC. 1.6.4.2.), and superoxide dismutase (SOD, EC. 1.15.1.1) appear to be the most sensitive to radical proliferation (Wenning and Di Giulio 1988; Livingstone et al. 1999; Porte et al. 1991; Sole et al. 1994; Regoli and Principato 1995; Labrot et al. 1996; Regoli et al. 1998). The modulation of antioxidant enzymes by heavy metals, linked to oxidative stress, has been observed in marine invertebrates, principally in molluscs. Although, these enzymes are potential biomarkers for environmental stress, they have seldom been used for this purpose in different taxonomic groups for hypothesis testing. In general, the evaluation of the responses of antioxidant enzymes in marine invertebrates related to heavy metal exposure and the understanding of these processes involved is scanty. This paper examines the effects of a short-term, sublethal copper exposure on membrane peroxidation (MDA) and antioxidant enzyme biomarkers in the polychaete Eurythoe complanata (fire worm; Amphinomidae). This cosmopolitan tropical organism has proved suitable as a bioindicator for testing benthic pollution (Marcano et al. 1997; Nusetti et al. 1998).