Electrophysiological responses of gustatory sensilla of Mamestra brassicae (Lepidoptera, Noctuidae) larvae to three ecdysteroids: ecdysone, 20-hydroxyecdysone and ponasterone A.

Specialised phytophagous Lepidoptera such as Bombyx mori and Pieris brassicae have contact chemoreceptors that perceive ecdysteroids at very low concentrations. This sensory perception allows them to feed on substrates with a high content of phytoecdysteroids. We have evaluated if a polyphagous insect like Mamestra brassicae does possess contact chemoreceptor cells that are sensitive to these molecules. Electrophysiological recordings were performed from contact chemoreceptors located on the maxilla. These receptors were stimulated with some sugars, amino acids and salts and with three ecdysteroids. Our results demonstrate that a specific cell within the lateral sensilla responds to 20-hydroxyecdysone and ponasterone A but not to ecdysone.