Estimation of the Acetylcholinesterase activity of honey bees in Nepal

Decline in honey bee colonies possess a serious threat to biodiversity and agriculture. Prior detection of the stresses with the help of biomarkers and their management ensures honey bees survivability. Acetylcholinesterase (AChE) is a promising biomarker to monitor exposure of honey bees towards environmental pollutants. In this preliminary study, we measured AChE activity in forager honey bees collected from six districts of Nepal, Kathmandu, Bhaktapur, Lalitpur, Chitwan, Rupandehi and Pyuthan during autumn and winter seasons. We estimated AChE tissue and specific activities from bees heads using commercial kit based on Ellman assay and protein concentration using Lowry assay. In total, we collected 716 foragers belonging to A. cerana, A. mellifera and A. dorsata. A significant increase in all three parameters measured: AChE tissue activity, AChE specific activity and protein concentration was observed in winter samples. Both AChE tissue and specific activities were lower in A. mellifera compared to either A. cerana or A. dorsata. Protein concentration was higher in A. mellifera than in A. dorsata and lower than in A. cerana. We show correlation between both AChE tissue and specific activities and protein concentration across season and species and discuss possible factors contributing to the observations. Our results clearly indicate the presence of stress in the winter which is manifested through overexpression of the AChE. We recommend a detailed study to determine the factors accountable for the stresses for better management of honey bees in Nepal.