Abstract

Pesticides are agricultural tools used to control populations of pests, which include specific herbs, weeds, and insects. However, non-target organisms are often affected by the compounds within pesticides. For example, insecticides containing imidacloprid, a neonicotinoid, have been suggested to impair learning, memory, and cognition of honey bees (A. mellifera) and are linked to a decrease in size and density of neuronal synapses. Previous research focused on the mortality and toxicity of acute imidacloprid exposure on honey bees. However, the importance of determining sub-lethal effects is becoming increasingly evident. Moreover, honey bees living in the modern world are likely exposed to a cocktail of chemicals in low doses throughout their life. Our research focuses on understanding the impact of chronic, sub-lethal exposure to imidacloprid on physiological measures. We measured changes in synaptic structures in the honey bee brain following 7 days of sub-lethal pesticide exposure. In order to further elucidate the potential mechanism of the imidacloprid-induced changes, we utilized Caenorhabditis elegans, a free-living nematode and natural soil decomposer, which is genetically tractable and has a fully mapped neuronal connectome and genome. We measured the fluorescence of cholinergic neurons in C. elegans labeled through transgenic fluorescent reporters following long-term treatment with imidacloprid. We found a decrease in the intensity of cholinergic-associated fluorescence. Together with the neuronal changes in honey bees, this study seeks to provide physiological information related to a modern agricultural issue.