Cricket combined mechanoreceptors and kicking response

Abstract

1. Only those filiform hairs on the cerci ofGryllus, which are coupled with campaniform sensilla, show a) a thickening of the hair shaft at the height of the upper ring lamella of their sockets and b) a thin cuticular membrane, which surrounds their sockets. While thefiliform hairs themselves are deflected either parallel to the long axis of the cerci or perpendicular to it, thesockets of the filiform hairs may be deflected preferentially in the proximal and distal direction. 2. Spike potentials can be recorded from the sensory cells of the filiform hairs as long as these are deflected in a weak air current, but not during permanent deflection in strong air streams when they touch the inner wall of their sockets (Fig. 5). The sensory cells of the campaniform sensilla respond to deflection of the sockets in a phasic manner. All of the investigated campaniform sensilla respond to a deflection of the sockets in either the proximal or the distal direction. 3. Air currents of a speed, strong enough to deflect the sockets of the filiform hairs and thus to excite the campaniform sensilla, result in an increase of kicking responses from about 10–20% to nearly 100%. We conclude that the campaniform sensilla on the cercus ofGryllus trigger the kicking response. 4. Through the functional coupling of filiform hairs with campaniform sensilla the working range of these combined organs is considerably extended. Up to a speed of air currents of 1.9 m/s only filiform hairs respond. Stronger stimuli of up to 2.3 m/s (stimulation parallel to the long axis of the cerci) or of up to 3.6 m/s (stimulation perpendicular to the long axis of the cerci) deflect the sockets and result in a response of the campaniform sensilla.