Comparative sucrose responsiveness in Apis mellifera and A. cerana foragers

Abstract

In the European honey bee, Apis mellifera, pollen foragers have a higher sucrose responsiveness than nectar foragers when tested using a proboscis extension response (PER) assay. In addition, Africanized honey bees have a higher sucrose responsiveness than European honey bees. Based on the biology of the Eastern honey bee, A. cerana, we hypothesized that A. cerana should also have a higher responsiveness to sucrose than A. mellifera. To test this hypothesis, we compared the sucrose thresholds of pollen foragers and nectar foragers in both A. cerana and A. mellifera in Fujian Province, China. Pollen foragers were more responsive to sucrose than nectar foragers in both species, consistent with previous studies. However, contrary to our hypothesis, A. mellifera was more responsive than A. cerana. We also demonstrated that this higher sucrose responsiveness in A. mellifera was not due to differences in the colony environment by co-fostering two species of bees in the same mixed-species colonies. Because A. mellifera foragers were more responsive to sucrose, we predicted that their nectar foragers should bring in less concentrated nectar compared to that of A. cerana. However, we found no differences between the two species. We conclude that A. cerana shows a different pattern in sucrose responsiveness from that of Africanized bees. There may be other mechanisms that enable A. cerana to perform well in areas with sparse nectar resources.

Figure 1. Percentage of bees showing proboscis extension response (mean+SE) of pollen (P, solid) and nectar (N, empty) foragers of Apis mellifera (triangles) and A. cerana (circles) in their own colonies, across different sucrose concentrations (plotted as log scale but with actual concentrations).

A: unfed foragers tested directly, Data based on 10 colonies per species (N = 600 bees). B: foragers tested 30 min after being fed 5μl 30% sucrose solution. Data based on 5 colonies per species (N = 300 bees).

Figure 2. Percentage of bees showing proboscis extension response (mean+SE) of pollen (P, solid) and nectar (N, empty) foragers of Apis mellifera (triangles) and A. cerana (circles) of unknown-aged foragers in mixed-species colonies, across different sucrose concentrations (plotted as log scale but with actual concentrations).

Data based on 3 mixed-species colonies (N = 3 x 2 x 2 x 10 = 120 bees).

Figure 3. Percentage of bees showing proboscis extension response (mean+SE) of 14-day-old workers from three mixed-species colonies, of Apis mellifera (triangles) and A. cerana (circles).

%PER were significantly higher in A. mellifera than A. cerana. Data based on 3 mixed-species colonies (N = 60 bees).

Figure 4. Sugar concentrations from crop of returning foragers of A. cerana (empty) and A. mellfiera (hatched).

A: The average sugar concentrations of foragers caught each hour in both species; B: The lowest sugar concentration during each hour from foragers of both species.