Honeybees are able to represent during trophallaxis instantaneous changes in flow of solution

WAINSELBOIM, ALEJANDRO JAVIER; FARINA, WALTER MARCELO; ROCES, FLAVIO

Foz de Iguazú, Brasil

Congreso; XXI International Congress of Entomology; 2000

 The coordination of tasks in honeybee colonies requires the exchange of information between members of the hive through different communication channels such as pheromones, dancing behavior and trophallaxis. Trophallaxis is the mouth to mouth exchange of liquid food from a donor to a recipient bee and is most important when foragers return to the hive after a successful food-gathering trip. These foragers completely unload their nectar crop content to one or more simultaneous recipient bees before leaving the hive for a new foraging bout. Experiments with donor foragers gathering sucrose solution at a regulated-flow feeder showed that the rate at which the liquid food is unloaded (transfer rate) depends on the flow of solution encountered by the donor at the feeder. Thus, foragers finding a higher flow of solution at the food source will deliver the collected solution at a higher rate once in the hive. What remained to be seen was whether foragers monitored the flow of solution offered by the feeder, or the time they remained at the food source (feeding time), since with increasing flow of solution feeding time decreases. To address this question, donor foragers were trained to a regulated-flow feeder offering a 50% w/w sucrose solution. After the fifth visit was complete the bee was captured and placed inside an acrylic box together with an empty recipient from the same hive. Transfer rate during the subsequent trophallactic encounter was recorded. The experimental series performed were: (a) donors were trained to a flow of 10, 20 or 60 µl/min. (feeding time=6, 3 or 1 min. respectively); (b) donors were trained to a flow of 20 µl/min in the first 4 visits and were offered 60 µl/min, in the initial 30 seconds and 10 µl/min. in the final 2.5 minutes of the fifth visit; (c) foragers were trained as in (b) but were offered 10 µl/min. during the initial 2.5 minutes of the visit and 60 µl/min in the final 30 seconds of the fifth visit. Transfer rate measured after the fifth visit was found to be related to the flow of solution found in that visit. In (a) transfer rate increased with increasing flow of solution, as expected from previous results. In (b) transfer rate decreased significantly compared to animals that experienced 20 µl/min. throughout the five visits. In (c) two populations of bees were found: one of them transferred solution at the same rate than those that found 60 µl/min. during all five visits, another group showed the same response as in (b). Thus foragers detected the change of flow at the food source, regulating transfer rate in relation to the new conditions found at the feeder, despite the fact that feeding time was kept constant. This study was supported by founds from a PWA-Program (DAAD, Germany, and Fundación Antorchas, Argentina) and ANPCYT (PICT 98-03103). Index terms: Apis mellifera, forager, communication.