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Abstract

Host selection by conifer-inhabiting bark beetles is governed by pheromones from conspecifics and kairomones from host trees. The response to attractive odours is inhibited by non-host volatiles (NHV), originating from angiosperm trees. For the European spruce bark beetle (Ips typographus), the importance of aggregation pheromone and inhibitory NHV has been demonstrated, whereas the role of host kairomones in host location is questionable. Several inhibitory NHV have been identified, some with redundant, others with synergistic effects. By means of electrophysiological recordings from single olfactory receptor neurones (ORNs), we investigate the relative proportions of ORNs that respond to pheromones, host, and non-host volatiles, respectively, and we look for spatial distribution patterns among ORN types. We also study whether the behavioural pattern of redundancy and synergism among NHV is reflected at the antennal level of olfaction. Although we are at an early stage, clear functional patterns have emerged. Most ORNs respond specifically to one or a few compounds. In both sexes, pheromone sensitive ORNs seem to be more common than ORNs tuned to host or non-host volatiles, respectively. For one of the compounds (cis-verbenol), ORNs are mainly present on the distal part of the antennae. Selective ORNs that respond to host compounds exist, suggesting that volatiles released from conifers might be relevant in host location. In addition, at least four ORN types that are sensitive to NHV have been found. The response specificity of these neurones seems to partly explain the behavioural patterns of redundancy and synergism among active NHV. Synergizing compounds appear to be perceived by selective ORNs, while somewhat more broadly tuned ORNs respond to redundant compounds. However, we are careful to draw any definite conclusions until response specificity has been studied at lower stimulus doses. Yet, the preliminary results indicate that this study may provide a basis for how different attractive, and especially inhibitory signals, are integrated in the insects’ olfactory system

Published in

Publisher: ESITO

Conference

10th European Symposium for Insect Taste and Olfaction (10th ESITO)

SLU Authors

UKÄ Subject classification

Forest Science
Environmental Sciences and Nature Conservation

Permanent link to this page (URI)

https://res.slu.se/id/publ/16558