Individual olfactory learning and memory in the ants Camponotus fellah

ESCHBACH, C; JOSENS, R; GIURFA, M

Villetaneuse- Paris, France

Otro; 41e Colloque de la Société Française pur l'Etudes du Comportement Animal; 2007

Société Française pur l'Etudes du Comportement Animal (SFECA)

Ants of the genus Camponotus are capable of individual associative olfactory learning under controlled laboratory conditions. Their olfactory learning abilities were recently characterized by using a Y-maze, in which ants had to discriminate between two pure odorants, limonene and octanal, one rewarded with sucrose solution and the other punished with quinine solution. Ants learned the discrimination after 16 trials but no assays were performed to estimate the duration and robustness of the associative memory established. Associative learning and memory in insects are modulated by biogenic amines which may act as substitutes for appetitive or aversive reinforcements. These amines depress or facilitate a wide range of insect behaviours but nothing is known about their possible modulatory role in olfactory learning and memory in ants. We therefore performed a series of experiments aimed at characterizing 1) olfactory associative memory and 2) the effect of octopamine and dopamine on olfactory acquisition and memory in C. fellah ants. In a first experiment, we trained ants as described above and tested them with the odours previously learned presented without reinforcements. Tests were performed at 24h or 72h post acquisition in order to determine whether memory could be retrieved successfully at these periods. In both tests, ants chose significantly the previously rewarded odour and spent more time in the arm of the Y-maze presenting this odour. No extinction of these performances was visible, even after five consecutive non-reinforced retention tests. These results show that olfactory associative long-term memories are established in the C. fellah brain and that these long-term memories are extremely stable and robust. In the second experiment, we studied the effect of dopamine (DA) and octopamine (OA) on olfactory learning and memory. Amines were orally administrated in the sucrose solution fed to the ants. An independent group of 75 ants each was used for each treatment: OA, DA and Control. Ants were trained as before and their acquisition and retention performances recorded. Preliminary results show that DA-treated ants learned faster the association than OA-treated and control ones. The performances observed at the end of the conditioning are the same in the DA and OA groups and slightly inferior in the control one. No difference between groups was found in the retention tests. During conditioning, DA also exerted a facilitatory effect on the time needed to return to the set up. This effect was particularly visible in the last block of conditioning. Our results thus suggest a facilitatory action of DA on olfactory learning in ants.