Evaluation of the ecotoxicological stress induced by anthropogenic contaminants in Apis mellifera

A rapid decline of Apis mellifera, a keystone pollinator of wild plant species and agricultural crops, was recorded worldwide in recent years. The massive use of pesticides in agriculture associated with pollution generated by other human activities and presence of parasites, can cause toxicological effects in bees including a decrease of the immune defenses, leading to collapse of the colonies. In order to adequately monitor these pollinating organisms, it is necessary to develop and apply highly sensitive and integrated ecotoxicological investigation methods. The aim of this study was to develop and apply a set of ecotoxicological biomarkers to study the effects of environmental contaminants on bees. In a first phase we investigated in the laboratory the effects of EMS, cadmium and a commercial fungicide (Amistar®xtra) in adult honey bees, evaluating eventual variation in glutathione S-transferase (GST) and acetylcholinesterase (AChE) activities, erythrocyte nuclear abnormalities (ENA) assay and differential haemocytes count (DHC). Genotoxic effects as well alteration of the immune system were found in bees treated with EMS, cadmium or the fungicide. Cadmium and Amistar®xtra also inhibited AChE activity, GST was induced by the fungicide and by EMS. In a second phase adult honey bees were collected from apiaries located in four environments characterized by different chemical input: a wooded environment (low input), an urban site, an orchard and a cultivated countryside site. ENA assay showed that bees taken from the countryside and the orchard had a greater number of abnormalities compared to the forest, confirming the presence of genotoxic substances in agricultural environments compared to control environments. GST was induced in bees from the urban environment, AChE was found to be inhibited in the countryside compared to the forest, suggesting the presence of substances with neurotoxic effect in this environment.