Toxicidade da clotianidina para a abelha africanizada Apis mellifera Linnaeus (Hymenoptera:Apidae)

Abstract

Bees belonging the genus Apis are extremely important either for their hive products or by providing the pollination service. However, in agricultural fields, the use of pesticides affects not only the target organisms but expose the beneficial insects as for example bees. Thus, the objective of this study was to determine the acute toxicity (LD50) of clothianidin to Apis mellifera L., 1758 and assess its sublethal effects. The LD50 was obtained by topical application of clothianidin at different concentrations on bee thorax, being the value estimated of 6.67 ng/bee. Afterward, experiments were done to evaluate the possible effects of the sublethal doses equivalent to 1/400 and 1/20 of the LD50 and acetone for the control. For the survival assay, three ways of bee contaminations were assessed: topical, oral and contaminated surface. Was also assessed the Proboscis extension reflex as measure to detect any impairment of the cognition ability of bees intoxicated with clothianidin. In another bioassay, insects were exposed to the different doses of clothianidin and the activity of the enzymes acetylcholinesterase, carboxylesterase, alkaline phosphatase and glutathione-s-transferase, were assessed for third and fourth instars of larva and for the adult of A. mellifera. Independent of the exposure of bees, clothianidin reduced the longevity of insects and in parts affects negatively the Proboscis extension reflex test. From the study with enzymes, the activities of acetylcholinesterase, alkaline phosphatase, carboxylesterase and glutathione S-transferase in insects exposed to clothianidin, observed changes resulting from the presence of the insecticide. The clothianidin was toxic to A. mellifera when evaluated using biological, biochemical and behavioral approaches. However, new studies should be performed to confirm the toxicity of clothianidin to A. mellifera Africanized using high tier levels.