Diet effects on honeybee immunocompetence

Abstract

The maintenance of the immune system can be costly, and a lack of dietary protein can increase the susceptibility of organisms to disease. However, few studies have investigated the relationship between protein nutrition and immunity in insects. Here, we tested in honeybees (Apis mellifera) whether dietary protein quantity (monofloral pollen) and diet diversity (polyfloral pollen) can shape baseline immunocompetence (IC) by measuring parameters of individual immunity (haemocyte concentration, fat body content and phenoloxidase activity) and glucose oxidase (GOX) activity, which enables bees to sterilize colony and brood food, as a parameter of social immunity. Protein feeding modified both individual and social IC but increases in dietary protein quantity did not enhance IC. However, diet diversity increased IC levels. In particular, polyfloral diets induced higher GOX activity compared with monofloral diets, including protein-richer diets. These results suggest a link between protein nutrition and immunity in honeybees and underscore the critical role of resource availability on pollinator health.

Figure 1.

Effect of pollen diet on IC in 5 (open bars) and 10 days old bees (filled bars). (a) Haemocyte concentration, (b) phenoloxidase activity, (c) fat body mass and (d) GOX activity. Eight bees per cage for each experimental group were analysed for each immune parameter. The protein percentage of each pollen diet is indicated on the x-axis. Each letter indicates significant differences between diets (p < 0.05, Newman–Keuls post hoc tests). No significant interaction between the diet and age factors was found (p > 0.05 for each immune parameter). Data show mean ± s.e.