Identification of sensilla involved in taste mediation in adult western corn rootworm (Diabrotica virgifera virgifera LeConte).
A group of sensilla present on the maxillary galea of adult western corn rootworm,Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) beetles has been identified morphologically and physiologically to be involved in taste mediation. There are approximately 15 chemosensory hairs on each galea. Bilateral removal of these structures resulted in a significantly reduced consumption of a strongly phagostimulant triterpenoid, cucurbitacin B, and led to increased ingestion of a phagodeterrent alkaloid, strychnine. Electrophysiological responses obtained via tip-recording of galeal chemosensilla with submillimolar concentrations of host and nonhost plant compounds resulted in dose responses overlapping with the effective behavioral ranges. Cucurbitacin B was found to evoke chemosensory responses at levels as low as 0.1µM. Sinceγ-aminobutyric acid (GABA) is an agonist. (-)-β-hydrastine and strychnine are antagonists, and cucurbitacin B has been proposed to act at a separate modulatory site of classical synaptic GABA and glycine receptor-channel complexes, results reported here raise the possibility that there are peripheral chemosensory receptor sites that may resemble, functionally and structurally, synaptic receptor sites in the central nervous system.
Department of Entomology, The Pennsylvania State University, 16802, University Park, Pennsylvania.
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