Impact of carbohydrate sources on the longevity and physiological traits of the European honey bee workers

Carbohydrates are vital for honey bee energy, fitness, and survival, influencing colony dynamics and resilience. This study examined the effects of various carbohydrate sources on honeybee longevity, hypopharyngeal gland size, gene expression, and gut microbiome composition. Newly emerged bees were fed white sugar, brown sugar, corn syrup (CS), maltose, acacia honey, chestnut honey, and oligosaccharide ad libitum. Bees fed CS showed the highest longevity, followed by acacia honey and white sugar, while oligosaccharide-fed bees had the lowest longevity. CS-fed bees also exhibited larger hypopharyngeal glands, correlating with improved survival. Gene expression analysis revealed upregulation of Ilp2 and Vg and downregulation of Ilp1 in 14-day-old bees fed with CS which may be linked to enhanced longevity. Gut microbiome analysis showed the higher composition of Frischella in honey fed treatment groups and Bartonella in processed carbohydrates treated groups, potentially compensating for dietary amino acid deficiencies. However, the absence of core symbionts like Snodgrassella in CS-fed bees may weaken immunity and heighten disease susceptibility. These findings suggest starch-derived corn syrup as a promising carbohydrate source under laboratory conditions, however, long-term colony-level studies are essential to fully understand its benefits and potential risks. This research provides valuable insights for honey bee management and conservation strategies.