RESUMO
DCOIT is a co-biocide that is part of the formulation of the commercial antifouling Sea-Nine 211® and although it is "safe to use", negative effects have been reported on the antioxidant defense system of non-target organisms. Therefore, the objective of this research was to verify and compare the response of antioxidant enzymes of juveniles and adults of Amarilladesma mactroides exposed to DCOIT. The animals were exposed to solvent control (DMSO 0.01%) and DCOIT (measured concentration 0.01 mg/L and 0.13 mg/L) for 96 h, then gills, digestive gland and mantle were collected for analysis of the enzymatic activity of glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT). The results revealed that adults, in relation to juveniles, have low basal activity of GST and SOD enzymes in the gills and digestive gland and high basal activity of SOD and CAT in the mantle. DCOIT did not alter GST activity in the gills of any life stage, while both concentrations decreased SOD and CAT in adults. In the digestive gland, it was observed that DCOIT (0.13 mg/L) decreased the GST activity in adults and CAT in juveniles, and both concentrations of the co-biocide decreased the SOD and CAT in adults. In the mantle, DCOIT (0.13 mg/L) increased CAT in juveniles. We conclude that juveniles have greater basal activity of antioxidant enzymes than adults and, in addition, DCOIT negatively affected the adults of A. mactroides, mainly decreasing the activity of GST, SOD and CAT in the gills and digestive gland of these organisms.