Exposing developing honey bees (Hymenoptera: Apidae) to hormone mimicking insect growth disruptors alters expression of endocrine related genes in brains

Within a honey bee colony, young worker bees care for and provision the queen, enabling her to lay
2000 or more eggs a day. However, this critical relationship may be negatively affected by exposure to
pesticides, which can occur when foragers return to the hive with contaminated resources. Previous
research has found negative effects of larval exposure to insect grown disruptors (IGD),
methoxyfenozide and pyriproxyfen, on adult responsiveness to artificial queen pheromone. The present
work investigates potential physiological and molecular mechanisms underpinning this behavioral
change by examining the development of hypopharyngeal glands and ovaries as well as the expression
of genes related to reproduction and worker endocrine signaling in brain and hypopharyngeal gland
tissues. Though hypopharyngeal gland and ovary development were not altered by developmental
exposure to IGDs, gene expression differed among treatments. Specifically, in the brain tissue, ilp1 was
down-regulated in bees exposed to pyriproxyfen during development, and Kr-h1 was down regulated in
both methoxyfenozide and pyriproxyfen exposed bees. In the hypopharyngeal glands, Kr-h1, EcR-A, EcR-
B, and E75 were upregulated in honey bees exposed to methoxyfenozide compared to those in the
pyriproxyfen or control treatments. Here we discuss these results and their potential implications for
the health and performance of honey bee colonies.