14th European Symposium for Insect Taste and Olfaction (ESITO) ABSTRACTS September 20-25, 2015 Villasimius (Cagliari – Italy) www.ice.mpg.de/esito Agustina Falibene, Flavio Roces, Wolfgang Rössler Department of Behavioral Physiology and Sociobiology, Biozentrum, University of Würzburg, Germany, [email protected] Odor learning in ants: synaptic plasticity associated with long-term avoidance memory formation Long-term behavioral changes related to learning and experience have been shown to be associated with structural remodeling in the brain. Leaf-cutting ants learn to avoid previously preferred plants after those are experienced to be harmful for their symbiotic fungus, a process that involves long-term olfactory memory. We studied the dynamics of brain microarchitectural changes after long-term olfactory memory formation following avoidance learning in Acromyrmex ambiguus. Quantification of synaptic complexes (microglomeruli, MG) in olfactory regions of the mushroom bodies (MB) at different times after learning revealed a transient change in MG densities. Two days after learning, lip MG density was higher than before learning. At days 4 and 15 after learning – when ants still showed plant avoidance – MG densities had decreased to the initial state. Changes were observed in the lip but not in the visual collar in which MG densities remained unaffected. Furthermore, enriched experience such as the simultaneous collection of several, instead of one, non-harmful plant species resulted in a decrease in MG densities (pruning). The results indicate that learning and sensory experience affect the synaptic architecture of the MB calyces via different processes. While sensory experience leads to MG pruning in the MB olfactory lip, long-term memory formation appears to involve growth of new MG followed by the elimination of others. Supported by DAAD (A/11/76441) and DFG SFB 1047 Insect timing (projects B6 and C1). Ahmed A. M. Mohamed, Tom Retzke, Markus Knaden, Bill S. Hansson & Silke Sachse Max Planck Institute for Chemical Ecology, Jena, Germany, [email protected] To go or not to go? Olfactory processing of odor features: Good vs. Bad Natural olfactory stimuli are mainly composed of complex blends of volatiles, which might be mixtures of attractive and aversive odors. The identities and ratios of these odor components need to be evaluated by the fly to decide whether the odor mixture is still attractive or has shifted to an aversive stimulus. Despite this importance, the mechanism by which the olfactory system processes and integrates this complex information remains so far unclear. By combining behavioral experiments - using the FlyWalk - with neurophysiological experiments - using functional calcium imaging at different processing levels of the fly brain - we aim at understanding how and where the information about odor valence, i.e. attractive and aversive odors, is encoded and ultimately integrated along the olfactory pathway. The first results of the behavioral assay show that Drosophila adults behave differently when they are faced to different ratios of odor mixtures of attractive and aversive odors. The flies are strongly attracted to a mixture of an attractive food odor (ethyl acetate) and a well- known fly repellent (benzaldehyde) when the attractive odor occurs at high concentration. However, if the concentration of the attractive odor is decreased, the flies get less attracted, i.e. the aversive odor suddenly dominates the mixture. Remarkably, our imaging results show that this integration of attractive and aversive odors seem to take place already at the output level of the antennal lobe, i.e. at the level of the projection neurons. We are planning to silence different populations of LNs to identify those 2 neurons that are evoking mixture interactions and therefore mediating the integration of odors with opposing valences. Alexander Haverkamp, Julia Bing, Bill S. Hansson, Markus Knaden Max Planck Institute for Chemical Ecology, Department of evolutionary Neuroethology, [email protected] Optimal foraging by smell The intimate relationship between sphingid moths and the flowers they pollinate is a long standing model system for insect-plant coevolution. Pollinator shifts and pollinator preferences have been argued as the main forces driving this coadaptation; however the preference of hawkmoths for flowers with a matching corolla still remains controversial. The hawkmoth Manduca sexta visits a variety of night-blooming flowers. While foraging, it relies mainly on olfactory information and a preference for flowers emitting aromatic compounds and terpenes has been demonstrated. First, we used the close relationship between Manduca and different plant species within the Nicotiana genus to test for a relationship between olfactory preference and the match of proboscis and flower length. 3-d flight tracking of moths entering a well characterized flower odor plume revealed significantly higher upwind speeds and more source contacts when the headspace of matching flowers was presented, indicating that the olfactory preference of Manduca relates to the match of proboscis and flower. We next tested whether the moth gains an advantage from foraging on matching flowers. Hawkmoths feed “on the wing” - making energetic costs an important factor of foraging. We balanced flower-handling costs measured by respirometry against the energy provided by floral nectar. The net energy gain was indeed highest for moths foraging on matching flowers. Hence, olfactory information enables moths to predict foraging outcomes and strengthens the coadaptation of pollinator and flower. Anthi A. Apostolopoulou, Saskia Köhn, Michael Lutz, Alexander Wüst, Lorena Mazija, Anna Rist, Giovanni Galizia, Alja Lüdke and Andreas S. Thum University of Konstanz, Department of Biology, Konstanz, Germany, andreas.thum@uni- konstanz.de The neuronal and molecular basis of caffeine taste signaling in Drosophila larvae Caffeine is a widely consumed substance for humans, which strongly affects behaviour. Yet, for humans and animals the molecular and neuronal background underlying caffeine perception and processing is not entirely understood. Here, we use Drosophila larva as a simple system to investigate caffeine information processing. In larvae, consumption of caffeine induces avoidance behaviour, suppresses feeding and decreases survival but, does not reinforce aversive odour associations. Only 12 gustatory neuron pairs co-express the bitter receptors Gr33a and Gr66a and these neurons are necessary for avoidance behaviour. We found that individual receptor gene mutants for these two genes show partially reduced caffeine avoidance. Performing a neuronal screen to pinpoint total loss of caffeine avoidance to single gustatory bitter neurons out of the Gr33a/Gr66a set identified a single Gr93a positive pair of dorsal pharyngeal sensilla that responded to caffeine. Likewise, Gr93a receptor gene function is necessary for caffeine avoidance. In conclusion, our data suggests that the detection of caffeine is encoded using a dedicated sensory channel for bitter sensation involving Gr93a. This finding opens new avenues to investigate how caffeine 3 affects behaviour by separating stimulation of the sensory system from internal brain functions. Andy Sombke, Elisabeth Lipke University of Greifswald; Zoological Institute and Museum; Dept. for Cytology and Evolutionary Biology, Germany, [email protected] Visualizing the antennal lobe using X-Ray microscopy – a new approach in arthropod neuroanatomy Traditionally, arthropod neuroanatomy is explored by methods such as classical histology or immunohistochemistry combined with fluorescence- or confocal laser scan microscopy. However, these methods are time consuming, prone to artifacts, and often require extensive sample preparations to obtain desired information. Furthermore, as a consequence of e.g., dissection or sectioning of the nervous system, or parts of it, information on the natural coherence is usually missing. Non-destructive approaches such as micro-computed X-ray tomography (µCT) overcome these limitations and have been shown to be a valuable tool in understanding and visualizing internal anatomy and structural complexity of a variety of studied taxa, including arthropods. Nevertheless, only little is known about the usability of this method for analyzing the architecture and organization of the arthropod nervous system. We analyzed the brains in representatives of several arthropod taxa and compare our results to previously obtained histological and immunohistochemical data. Our data show that the resolution obtained by µCT is sufficient to (1) analyze the overall organization as close to their natural state as possible, (2) distinguish specific neuropils, such as olfactory glomeruli of the antennal lobes, and (3) obtain quantitative data. Moreover, we compare and discuss limitations, as well the influence of staining and preliminary sample preparation procedures. Aniruddha Mitra and Frédéric Marion-Poll Laboratoire Evolution, Genomes, Comportement, Ecologie, Centre National de la Recherche Scientifique, Gif sur Yvette, France, [email protected] Volatile odorants activate taste neurons on the proboscis of Drosophila Taste and smell share the same function: detecting chemicals from the external world. Despite this common functionality, both systems are designed very differently both at the level of the sensory receptors and in the way information is mapped into the brain.