Abstract
Unlike the situation in most cockroach and cricket species studied so far, the windβsensitive cerci of the cave cricket Troglophilus neglectus Krauss (Rhaphidophoridae, Orthoptera) are not oriented parallel to the body axis but perpendicular to it. The effects of this difference on the morphology, and directional sensitivity of cercal giant interneurons (GIs), were investigated. In order to test the hypothesis that the 90Β° change in cercal orientation causes a corresponding shift in directional sensitivity of GIs, their responses in both the horizontal and vertical planes were tested.
One ventral and four dorsal GIs (corresponding to GIs 9β1a and 9β2a, 9β3a, 10β2a, 10β3a of gryllid crickets) were identified. The ventral GI 9β1a of Troglophilus differed somewhat from its cricket homologue in its dendritic arborisation and its directional sensitivity in the horizontal plane. The morphology and horizontal directionality of the dorsal GIs closely resembled that of their counterparts in gryllids. In the vertical plane, the directionality of all GIs tested was similar. They were all excited mainly by wind puffs from the axonβipsilateral quadrant. The results suggest that directional sensitivity to air currents in the horizontal plane is maintained despite the altered orientation of the cerci. This is presumably due to compensatory modifications in the directional pReferences of the filiform hairs. J. Exp. Zool. 292:73β81, 2002. Β© 2002 WileyβLiss, Inc.