Dietary phytochemicals support the development of hypopharyngeal glands in worker honey bees

Worldwide declines in pollinator populations has engendered intense research on the factors responsible for these declines. Of these, poor nutrition due to the disappearance of natural flowering habitat has been identified as a major player, particularly in the North American agricultural landscape wherein populations of the western honey bee, Apis mellifera, experience seasonally regimented monocultural diets. Lack of habitat diversity results in bees deprived of important micronutrients in floral nectar and pollen. Dietary supplements with micronutrients in the form of phytochemicals have been shown to augment longevity, pathogen tolerance and gut microbiome diversity. In this study, we determine the impact of phytochemical supplementation on the development of hypopharyngeal glands (HPG) in worker bees. Caged bees were allowed ad libitum access to sucrose solution with 25 ppm of phytochemical p-coumaric acid, kaempferol, gallic acid, or caffeine. The diameter of HPGs were measured at 10 days post-eclosion. We found that p-coumaric acid supplemented bees showed larger HPGs relative to controls. Although the other phytochemicals did not elicit the same reaction, the overall positive impact of dietary supplementation was demonstrated in nurse-age worker bees. HPGs are important for larval nutrition and our results suggest that access to important phytochemicals through diverse plants in the habitat could improve colony growth and performance through improved capacities for workers to nurse developing brood.