Dietary pollen and carbohydrate sources influence longevity, physiology, and gut microbiota in honey bee (Apis mellifera)

The Western honey bee (Apis mellifera) is essential for crop pollination and ecosystem stability and production for beekeepers as well, yet rising colony losses are a major concern. Poor nutrition is a key stressor, prompting beekeepers to supplement carbohydrates and proteins during nectar and pollen shortages. This study was conducted under controlled laboratory cage conditions to evaluate the interaction effects of two carbohydrate sources, regular corn syrup (rich in maltose) and sucrose syrup; and three pollen types (rapeseed, kiwi, and mixed pollen) on honey bee longevity and physiological performance. Bees fed corn syrup lived longer and developed larger hypopharyngeal glands (HPG) than those fed sucrose syrup. Among pollen treatments, mixed pollen produced the most favorable outcomes, including increased survival, larger HPG acini, and higher vitellogenin levels. The combination of corn syrup and mixed pollen (CS–MP) yielded the longest lifespan, and lowest food consumption, indicating improved nutritional efficiency. Gut microbiota composition varied with diet: RP and KP diets showed higher relative abundances of Sondgrassella and Gilliamella compared with MP whereas the mixed pollen diet promoted a higher relative abundance of Lactobacillus. These results demonstrate that optimizing carbohydrate and pollen combinations can significantly enhance honey bee health, longevity, and colony resilience, providing practical insights for nutritional management in apiculture.