Alterations of chemoreceptor function in army worm larvae (Spodoptera exempta) by a plant-derived sesquiterpenoid and by sulfhydryl reagents

ABSTRACT. Warburganal, a sesquiterpene dialdehyde from Warburgia sp., strongly suppressed the feeding response of Spodoptera exempta larvae to sucrose-flavoured agar. Its effect on chemoreceptive sensilla of S. exempta was investigated. After a latent period (of up to an hour, depending on concentration), sensilla treated with warburganal produced transient bursting discharges in several receptor cells. Subsequently, receptor responses to sucrose or meso-inositol were reversibly inhibited. These effects were abolished by mixing warburganal with cysteine or dithiothreitol (though not with other amino acids), and were qualitatively similar to the effects of the sulfhydryl reagents PCMB and NEM. The possible mode of action by which warburganal may act as an –SH acceptor and thereby affect energy transduction in the chemoreceptors is discussed.