Effects of dichlorvos aquaculture treatments on selected biomarkers of gilthead sea bream (Sparus aurata L.) fingerlings

The gilthead sea bream (Sparus aurata) is the most important marine cultured species in the Mediterranean. Dichlorvos is one of the main chemical agents used in bath treatments against ectoparasites of marine farmed fish. The main objective of this study was to investigate the effects of 24 h dichlorvos baths on selected biomarkers that are involved in important physiological functions or indicative of gilthead sea bream fingerlings growth. To attain this objective, the in vivo effects of dichlorvos on cholinesterases' activity (ChE), lipid peroxidation (TBARS), RNA/DNA ratio, glutathione S-transferases activity (GST) and heat shock proteins HSP70 were studied. The characterization of ChE in brain and muscle was previously determined to select the most sensitive tissue in this species. The exposure of gilthead sea bream fingerlings to dichlorvos caused an inhibition of ChE activity, an increase in lipid peroxidation (TBARS) and a decrease in the RNA/DNA ratio. In contrast, no significant changes in GST and HSP70 were found. The results indicate that ChE, TBARS and RNA/DNA ratio seem to be sensitive biomarkers to detect sub−lethal effects of dichlorvos aquaculture treatments in gilthead sea bream fingerlings.