Searching beyond the streetlight: neonicotinoid exposure alters the neurogenomic state of worker honey bees

Neonicotinoid insecticides have been implicated in honey bee declines, with many studies showing that sub-lethal exposure impacts bee behaviors such as foraging, learning and memory. Despite the large number of ecotoxicological studies carried out to date, most focus on a handful of worker phenotypes leading to a 'streetlight effect' where the a priori choice of phenotypes to measure may influence the results and conclusions arising from the studies. This bias can be overcome with the use of toxicological transcriptomics, where changes in gene expression can provide a more objective view of how pesticides alter animal physiology. Here, we used RNA sequencing to examine the changes in neurogenomic states of nurse and forager honey bees that were naturally exposed to neonicotinoids in the field and artificially exposed to neonicotinoid in a controlled experiment. Overall design: Field Experiment - 5 Honey bee colonies located immeditely near neonicotinoid treated corn field and 5 honey bee colonies located at least 3km away from such field. One May 30th, 2014, right after corn plantation, 5 forager bees and 5 nurse bees were collected from each colony. They were immdetely frozen on dry ice and later, their brains were dissected. Apiary Expeirment - Ten colonies in a single apiary received artificial pollen for a 12-week period. Half of the colonies received a pollen patty spiked with clothianidin; the most commonly found NNI in the field study. The exposure started with 4.9ppb of clothianidin in week 1 and was lowered each week, until the dose reached 2.0ppb at week 5 and stayed the same until week 12 . Five nurses and five foragers were collected from each queen-right colony 30 days after the start of our experiment