Morphological and electrophysiological characteristics of the epipharyngeal sensilla of the silkworm, <i>Bombyx mori</i>

Abstract

Abstract One pair of gustatory sensilla was found on the epipharynx of Bombyx mori larvae, and some morphological and electrophysiological characteristics of the epipharyngeal sensilla were investigated. They are sensilla coeloconica composed of a small papilla with a pore at the tip and a swelling of cuticle encircling the papilla. Three bipolar neurons innervate each sensillum. One neuron is an inositol receptor which responds to inositol only. Another cell responds with action potentials of relatively large amplitude to some feeding deterrent substances, such as strychnine nitrate. The thresholds of these cells for inositol and strychnine nitrate are approximately 10 −4 M and 10 −7 M, respectively. At least two kinds of spikes can be observed when these sensilla are stimulated with some salts and acids. Dose‐response relationships and time courses of responses to inositol and strychnine nitrate were also examined in this study.