The mechanism of sensory transduction in a mechanoreceptor. Functional stages in campaniform sensilla during the molting cycle.

Abstract

Ultrastructural modifications that cockroach [Blattella germanica and B. discoidalis] campaniform sensilla undergo at 3 major stages in the molting cycle are described; the sensilla are physiologically functional at all developmental stages leading to ecdysis. Late stage animals on the verge of ecdysis have 2 completely separate cuticles. The campaniform sensillum sends a 220-.mu.m extension of the sensory process through a hole in its cap in the new (inner) cuticle across a fluid-filled molting space to its functional insertion in the cap in the old (outer) cuticle. Mechanical stimulation of the old cap excites the sensillum. The ultrastructural geometry of late stage sensilla, coupled with the observation they are physiologically functional, supports the hypotheses that sensory transduction occurs at the tip of the sensory process, and that cap indentation causes the cap cuticle to pinch the tip of the sensory process, thereby stimulating the sensillum.