Moist and dry hygroreceptors for relative humidity of the cockroach,Periplaneta americana L.

Abstract

Antennal hygroreceptors of the cockroach,Periplaneta americana L. have been electrophysiologically investigated. 1. The moist and dry hygroreceptors, together with a thermal receptor, are contained in a sensillum capitulum, which is located on alternating flagellar segments (Fig. 3). 2. The responses of both hygroreceptors are of a phasic-tonic manner, and following the cessation of stimulation, decrease to a level lower than the prestimulation level (Figs. 4, 5). 3. The humidity-response relationship of the hygroreceptors is independent of stimulus flux (Fig. 7). 4. The responses of the hygroreceptors, when the whole animal and stimulus air are changed simultaneously, are larger at higher than at lower temperatures. The normalized humidity-response relationship of the hygroreceptors at different temperatures are coincident when plotted against relative humidity but not when plotted against absolute humidity (Figs. 8, 10). 5. The humidity-response relationships at different temperatures are coincident when plotted against relative humidity, but not when plotted against absolute humidity, provided that only the stimulus temperature is changed (Figs. 9, 11). 6. We conclude that the responses of the hygroreceptors depend on the relative humidity and that the mechanism of the primary process of hygroreception is non-chemical.