Effect of bee bread on Africanized honey bees infected with spores of Nosema spp.

Abstract

Floral diversity allows honey bees, Apis mellifera L. (including its hybrids between subspecies) (Hymenoptera: Apidae), to meet their nutritional requirements. However, infection by Nosema spp. (Microsporidia: Nosematidae) destroys a bee's digestive epithelium, hindering the ability to absorb nutrients. In some subtropical regions, such as the Yucatan Peninsula, Mexico, nosemosis is one of the most widespread diseases in commercial apiaries. To date, there have been no reports of colony deaths attributable to the disease. It is possible that the naturally occurring diet in the Yucatan Peninsula sustains honey bee health. We tested this hypothesis by evaluating the effect of four diets – bee bread collected in the Yucatan's rainy and dry seasons, sucrose syrup, and a pollen substitute – on the response of caged Africanized honey bees (A. m. scutellata × A. m. adansonii × A. mellifera) to nosemosis infection (treatment with spores of Nosema apis Zander and Nosema ceranae Fries). We found that infected and uninfected bees consumed food in similar amounts regardless of the diet, although, overall, they fed at significantly lower rates when provided the pollen-substitute diet. Bees fed either of the bee bread diets had relatively low fat-body weight and expression of Vg, proPO, and GOx genes, three genes related to immune function. Bees fed sucrose syrup had low fat-body weight but relatively high gene expression. Infection from Nosema spores only reduced the individual survival probability for bees fed the bee bread collected in the dry season, yet bees fed the dry-season bee bread had the lowest infection rates. Our results indicate that natural stored bee bread in honey bee colonies from the Yucatan Peninsula could be one of the main factors influencing their survival and reducing Nosema spp. spore load.