Crop Load Links Gustatory and Feeding Responses to Foraging Specialization in Honey Bees

Honey bee foragers specializing in nectar, pollen, and water collection differ in their physiological demands and in how the collected resource is transported. Here, we investigated whether physiological and behavioral differences among forager types are associated with crop load, the amount of solution carried in the crop. Alternatively, we tested whether crop sugar concentration was more closely related to foraging specialization. We compared sucrose responsiveness, sucrose ingestion, crop load, and crop sugar concentration in nectar, pollen, and water foragers at the beginning and end of the foraging visit. At the beginning of the visit, pollen foragers carried the heaviest crop loads with the highest sugar concentrations and showed the lowest sucrose responsiveness and ingestion, whereas nectar foragers carried lighter crop loads with intermediate sugar concentrations and showed higher responsiveness and ingestion. Water foragers exhibited the lightest and most dilute crop contents and the highest sucrose responsiveness and ingestion. By the end of the visit, nectar foragers showed reduced responsiveness and ingestion as their crop loads increased, whereas pollen foragers showed the opposite pattern as their crop loads decreased. Notably, water foragers also showed reduced sucrose responsiveness and ingestion as their crop loads increased, despite a marked decrease in crop sugar concentration. In water foragers, crop load and crop sugar concentration changed in opposite directions, with behavioral responses consistently decreasing as crop load increased. Overall, these findings support a link between crop load and foraging specialization and suggest a role for crop distension in modulating sucrose responsiveness and feeding motivation in honey bees.