The proboscis extension response (PER) assay revealed the responsiveness of three subspecies of the honeybee
Apis mellifera [
A. m. jemenitica (
AMJ),
A. m. carnica (
AMC), and
A. m. ligustica (
AML)] to water and different concentrations (0.00001, 0.0001, 0.001, 0.01, 0.1, 0.5, 1.0, and 1.5 M) of three sugars (fructose, glucose, and sucrose) during the summer and fall seasons. The tested bee subspecies showed significantly different PERs to sugar types across the seasons. The water responsiveness of
AMJ, a native bee subspecies, was significantly lower than that of
AMC and
AML, which showed an equally higher water response in both seasons. During the summer season,
AMJ and
AMC were equally responsive to each sugar type at all tested concentrations.
AML was relatively less responsive to glucose at 0.001, 0.001, 0.01, 0.1, 0.5, and 1.0 M than to fructose and sucrose during the summer season. During the fall season,
AMJ was equally responsive to glucose and sucrose at all tested concentrations but showed a significantly different response between fructose and sucrose at 0.001, 0.01, 0.1, 0.5, and 1.0 M concentrations. The PER of
AMJ to fructose was lower than that of glucose and sucrose.
AMC was equally responsive to all tested sugars at all concentrations, and
AML showed a differential response between glucose and sucrose at different concentrations during the fall season. The inter-specific species comparisons revealed that all tested subspecies were equally responsive to fructose at all tested concentrations, and
AMJ was more responsive to glucose and sucrose than
AMC and
AML during both seasons.
AMC and
AML showed no differences in PER to glucose and sucrose in either season. The
AMJ, AMC, and
AML nectar and pollen foragers showed no significant differences in PER to glucose and sucrose. The
AMC nectar foragers were highly responsive to sucrose than pollen foragers at higher sucrose concentrations (0.1, 0.5, 1.0, and 1.5 M). The
AML (nectar forager vs. pollen forgers) showed identical PER to sucrose and glucose but a higher response of nectar foragers to high glucose concentrations (0.5, 1.0, and 1.5 M) than pollen foragers. For water responsiveness,
AMJ nectar and pollen foragers showed similar PER to water, whereas
AMC and
AML pollen foragers were significantly more responsive to water than nectar foragers.
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