Effects of the neonicotinoid insecticide Imidacloprid and the fungicide Pyraclostrobin on the solitary bee Tetrapedia diversipes: evaluation of energy metabolism, cellular responses and composition of the microbiome

Abstract

It is known that the population density of bees, as well as other pollinators, has been declining for some years, reaching worrying levels that would affect the pollination of natural and agricultural ecosystems. One of the determining factors for this situation is the use of pesticides such as herbicides, fungicides and insecticides, which used both in isolation and in combinations, often have not only action on pests and pathogens, but end up also reaching beneficial insects associated with crops, like bees. However, in several countries, the risk assessment of pesticides on pollinating insects is based on toxicity tests performed only with Apis mellifera, the most studied species. But, the vast majority of known bee species are solitary, representing 85% of the Apiforms. There is a lack of data in the literature on the effect of pesticides on Brazilian solitary bees, which could be useful to assess the need for the inclusion of representative species in risk assessment studies in Brazil. Given the above, the present study intends to evaluate the effect on solitary bees Tetrapedia diversipes of residual doses of neonicotinoid imidacloprid and its action in association with the fungicide pyraclostrobin, both widely used in Brazilian agricultural cultures. For that, the brain, the intestine, and the fat body will be evaluated for responses and adaptations to cellular stress by immunostaining Heat Shock Proteins (HSPs) and the Superoxide Dismutase Enzyme (SOD). In addition, cell death will be detected by DNA fragmentation by the TUNEL Reaction, and the damage to peritrophic matrix will be evaluated in the intestine of exposed bees. It is also intended to analyze the impact of pesticides on energy metabolism by quantifying ATP in fat body mitochondria. Another goal is to analyze the variation in the composition of the microbiome through a partnership established with Cornell University in the United States. The results generated in this project will be of great relevance to complement the data of the Thematic Project "Bee interactions - agriculture: Perspectives for sustainable use", showing possible synergistic or antagonistic effects of pesticides in solitary bees in which the toxicological effects are still not very well known. (AU)