Impact of different pollen protein diets on the physiology of Apis mellifera L. (Hymenoptera: Apidae) workers from essential plant sources

Background: The primary food sources for honey bees in colonies are processed nectar and fermented pollen. However, there are relatively few blooming plants that provide full sustenance to the bees, and their impacts on the physiology of honey bees in Pakistan have not yet been assessed. Diet with meager nutritional contents can affect various physiological parameters like hypopharyngeal glands (HPGs) sizes, rectal weight contents (RWCs), food intake and longevity of worker bees which indirectly affects overall colony development and make it vulnerable to diseases and pests. Methods: This study was designed to investigate the impact of protein diets in the form of different pollen on some physiological parameters of honey bee (Apis mellifera L.) from major plant sources serving as melliferous resources in the agro-climatic conditions of Dera Ismail Khan, Khyber Pakhtunkhwa, Pakistan. Results: Results indicated Brassica napus L. as the most effective pollen diet which took the highest time for 50 % of individuals’ mortality. B. napus L. also gave the highest increase of HPG size (278.47 µm) followed by Trifolium alaxandrinum L. Acacia modesta L., and Zea mays L., in comparison to sugar syrup (control) with 261.73, 237.49, 124.38 and 107.65 µm, respectively. Pollen intake followed a similar pattern, with B. napus having the highest levels (3.03 mg/bee/day), and bee bread (3.37 mg/bee/day), with an overall mean of 25.279. The overall mean for RWC demonstrates how easily the pollen diet may be digested. It was negatively correlated with the volume of rectal contents. When compared to pollen diets, honeybee workers given bee bread had the lowest overall mean (3.95 mg) for rectal contents, suggesting the greatest degree of digestibility. Conclusion: Diets from B. napus were taken and digested more quickly than those from A. modesta, Z. mays, and T. alaxandrinum.