Developmental exposure to hormone-mimicking insect growth disruptors alters expression of endocrine-related genes in worker honey bee (Hymenoptera: Apidae) brains and hypopharyngeal glands.

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 1,000 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-growth 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 the 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 downregulated in bees exposed to pyriproxyfen during development, and Kr-h1 was downregulated 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.

Drone Laying Honey Bee Workers in Queen Monitoring Cages.

Techniques to monitor honey bee (Apis mellifera) egg production in cages allow researchers to study how different environmental factors contribute to reproduction. However, although the conditions required to facilitate queen egg production in a laboratory setting have been established, limited work has addressed the requirements for stimulating and monitoring worker egg laying. Here, we documented that drone laying workers will lay eggs in Queen Monitoring Cages (QMC), specialized cages designed to facilitate queen egg laying under controlled conditions. Egg production and worker mortality were compared between QMCs containing queens and those containing drone laying workers. High-definition images of the last abdominal segments of living first-instar larvae hatched from worker laid eggs and those putatively laid by queens were qualitatively compared to identify candidate characteristics to determine their sex.