Biochemical Biomarkers in Individual Larvae of Chironomus xanthus (Rempel, 1939) (Diptera, Chironomidae)

Biochemical biomarkers have shown to be useful toxicity tools in environmental assessment programmes. However, few studies involving freshwater invertebrate species have been performed and even fewer on tropical species. The aim of this paper was to evaluate cholinesterase (ChE) and glutathione-S-transferase (GST) activities in larvae of Chironomus xanthus (Chironomidae, Diptera) exposed to the organophosphate parathion (ethyl) and the metals copper and cadmium. Considering ChE, significant reduction in activity was observed following C. xanthus exposure to parathion and cadmium (48 and 96 h, respectively). Inhibition of ChE activity (IC50) related to parathion seemed to be a more consistent and sensitive effect criteria than the LC50. For GST, there was significant reduction in activity following parathion exposure (48 h). Copper did not elicit any change in ChE or GST activities in C. xanthus. The findings of this paper show the two biomarkers as promising tools for assessing exposure to contaminats in tropical regions.