Contact chemoreceptors, known as basiconic sensilla in insects, occur dispersed and crow-ded in fields between mechanosensory recept-ors on the subgenital plate of the female des-ert locust Schistocerca gregaria and serve to control the chemical features of the substrate before and during oviposition. They represent about 26% of the total number of receptors (560 ± 5) identified on the subgenital plate. The distribution and peripheral innervation of the sensory system on the subgenital plate have been revealed by using the cobalt chloride backfill technique in a whole-mount preparation. In addition, the central nervous project-ions of a single basiconic sensillum have been identified in whole-mount prepa-ration by using neurobiotin backfill technique. The investigation showed that the 8th ventral abdominal nerve innervates the subgenital plate and a that all axons and neurites from one contact chemoreceptor usually stay close together in most of their projections in the central nervous system. The basiconic sensilla were sensitive to the different concentrations of sodium chloride (10 - 1000 mM) used and evoked excitation or inhibition in integrating interneurons. Two chemosensory interneurons integrating chemosensory information of sub-genital plate were identified based on intra-cellular staining with Lucifer Yellow. Each identified interneuron has a characteristic morphology defined by its array of branches in the regions of neuropil that provide its inputs and output to other neurons.
Key words: Subgenital plate, chemoreception, innervation, central projections, interneurons, Schistocerca gregaria
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