Developmental exposure to hormone mimicking insect growth disruptors alters expression of endocrine related genes in worker honey bee (hymenoptera: apidae) brains

Authors: LITSEY, ELIZA - University Of California, Davis; Fine, Julia

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2024
Publication Date: 1/30/2024
Citation: Litsey, E.M., Fine, J.D. 2024. Developmental exposure to hormone mimicking insect growth disruptors alters expression of endocrine related genes in worker honey bee (hymenoptera: apidae) brains. Journal of Economic Entomology. 117/377-387. https://doi.org/10.1093/jee/toae006.
DOI: https://doi.org/10.1093/jee/toae006

Interpretive Summary: Division of labor within a honey bee colony creates a codependence between bees that perform different jobs. The most obvious example of this is between the reproductive queen and worker bees. Queen bees lay 2000 or more eggs a day, while young worker bees tend and feed queens. Young workers and queens can be exposed to pesticides when foragers return to the hive with pesticide laden 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, suggesting that they would be less inclined to care for a queen. The present work investigates potential physiological and molecular mechanisms causing this behavioral change by examining physiological development as well as the expression of genes related to reproduction and worker endocrine signaling in brain and glandular tissues. Though we did not detect changes in physiology, endocrine related gene expression in tissues responsible for responses to stimuli and provisioning queens and larvae was affected by IGD exposure. Here we discuss these results and their potential implications for the health and performance of honey bee colonies.

Technical Abstract: Division of labor within a honey bee colony creates a codependence between bees performing different tasks. The most obvious example of this is between the reproductive queen and worker bees. Queen bees lay 2000 or more eggs a day, while young worker bees tend and feed queens. Young workers and queens can be exposed to pesticides 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. 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.