Gustatory responsiveness to pyrrolizidine alkaloids in the Senecio specialist, Tyria jacobaeae (Lepidoptera, Arctiidae)

• Published in: Physiological entomology 2004-03, Vol.29 (1), p.67-72
• Main Authors: Bernays, E.A, Hartmann, T, Chapman, R.F
• Format: Article
• Language: English
• Subjects: Arctiidae; chemical constituents of plants; chemoreceptors; dose response; duration; electrophysiology; feeding behavior; food plants; mouthparts; Neural sensitivity; phagostimulant; phagostimulants; phytophagous insects; pyrrolizidine alkaloid; pyrrolizidine alkaloids; Senecio; sensilla; taste sensitivity; taste threshold; Tyria jacobaeae
• ISSN: 0307-6962; 1365-3032
• DOI: 10.1111/j.1365-3032.2004.0366.x

Electrophysiological recordings from taste sensilla of the caterpillar Tyria jacobaeae with the pyrrolizidine alkaloids, characteristic compounds from their host plants, demonstrated sensitivity of a pyrrolizidine alkaloid-sensitive cell in the lateral galeal sensilla at concentrations as low as 1 x 10(-11) M. Another pyrrolizidine alkaloid-sensitive cell in the medial galeal sensilla responded at higher concentrations. Both pyrrolizidine alkaloid-cells were maximally sensitive to seneciphylline N-oxide and senecionine N-oxide. Seven other pyrrolizidine alkaloids were less stimulating. Monocrotaline N-oxide was the least stimulating. Observation experiments demonstrated that differences in sensitivity to different pyrrolizidine alkaloids at the electrophysiological level were correlated with differences in feeding behaviour; the first feeding bout was of longer duration on diet containing seneciphylline N-oxide than on diet containing monocrotaline N-oxide, and a plain diet was generally not accepted.