Early Olfactory Experience within an Appetitive Context in Honeybees, Apis mellifera L

A. ARENAS; WM. FARINA

Ribeirão Preto, São Paulo, Brazil

Congreso; International Conference on Tropical Bees and VI Encontro sobre Abelhas; 2004

Honey bee foragers easily adjust their olfactory memories to successive experiences such as changes in the floral availability. This plasticity allows them to shift from one memory to another when the situation calls for it, which is one of the main elements of their adaptability. It would be reasonable to think that pre-foraging olfactory experiences could give place to memory templates that might later be stronger than memories established during the actual foraging activities. These early experiences would bias, in the long term, the foraging bee behavior. We hypothesize that these pre-foraging experiences could conform long-term olfactory memories if acquired in an appetitive context, where the scent occurs together with a reward that circulates among workers inside the hive. In order to control the olfactory experience of pre foragers, groups of 60-80 individuals were kept in cages inside an incubator from the emergence to beginning of the foraging activities (predetermined in 17 days old). Throughout this period, bees were fed with ad-libitum sucrose solution. At different ages a pure odor was added to the solution (50ml/L) during four consecutive days (ages: 1-4, 5-8, 9-12 and 13-16). In day 17 bees were tested to the solution odor and to a novel one in a proboscis-extension paradigm. Also spontaneous response (SR) for 25 days-old bees was tested in the same way as before. The experiments were duplicated using two olfactory stimuli, linalool and phenilacetaldehyde. Results showed that bees in a foraging age could evoke olfactory memories towards the odor that was presented during pre-foraging stages. Moreover, not all the ages had the same response towards the solution odor, the bees that received the scented solution between days 5 and 8 and 13 and 16, presented the highest response levels when they were tested in day 17. For 25 days-old bees, a significant reduced SR for the treatment 9-12 days were found compared with the same response tested at day 17, while a lower but not significant SR was attained for treatments 1-4 and 5-8 days. The response pattern for the day 25 was however similar to that of the 17. In a second experiment, at a certain age (4, 6 and 10 days old) bees were conditioned at the proboscis-extension paradigm to one learning session, which consisted in two or three trails until bees learned. The SR pattern found at day 17 for these bees was similar compared with those with olfactory experiences acquired when scented solution was presented inside cages during four days. Present results suggest that foraging-aged bees can evoke olfactory memories acquired during pre-foraging ages. This process takes place during a relative narrow and early period of the adult life and occurs within an appetitive context. Then, results suggest that stable long-term memories acquired at the beginning of the adult stage persist throughout long periods, even in those in which the foraging tasks are the most relevant.