Speaker
Description
Specialist herbivores, rely on specific cues to identify their host plants; however, these innate stimuli are often difficult to detect from a distance and herbivores might learn to associate additional olfactory or visual information with these cues. For many butterflies, oviposition occurs only when specific gustatory cues are detected by the tarsi, allowing a mated female to identify ideal sites for offspring development. However, upon substrate location, simultaneously occurring stimuli might be integrated in memory and used in a later moment as additional cues to locate oviposition sites. In the present study, we asked whether mated Pieris brassicae butterflies are able to associate a novel olfactory stimulus, vanilla scent, with an innately meaningful oviposition stimulus, the glucosinolate sinigrin. In addition to this, we asked whether memory recall was dependent on the intensity of the neuronal response generated by sinigrin tarsal detection. In a first moment, mated butterflies were conditioned by exposure to a paper disc sprayed with different sinigrin concentrations and coupled with a vanilla scent source. To assess memory formation, animals were later exposed to the same paper discs used during conditioning, either bearing vanilla scent or a control solvent, but not sprayed with sinigrin. Memory recall was assessed by measuring 1) time spent on each disc type, 2) number of visits to each disc type, 3) number of oviposition events on each disc type. Tests were performed indoors (greenhouse) and outdoors (flight tent) and in both cases butterflies were able to form memory after conditioning. Moreover, electrophysiological recordings on the tarsal taste sensilla used to detect sinigrin allowed to observe that memory recall occurred only for animals conditioned with sinigrin concentrations giving the highest neuronal responses. This study presents novel insights on how butterflies can integrate different sensorial information to successfully complete crucial tasks such as oviposition, showing how cognitive plasticity might contribute to adaptation in a rapidly changing environment.
