Effect of a neuroendocrine factor on sex pheromone biosynthesis in the tomato looper, Chrysodeixis chalcites (Lepidoptera: Noctuidae)

Abstract

The presence of a pheromone biosynthesis activating neurohormone in the head gandlia, and its effect on the sex phermone biosynthetic pathway, were investigated in the tomato looper, Chrysodeixis chalcites (Esper). Comparison of pheromone components and precursor levels in the presence and absence of the factor was performed using untreated, ligated and ligated and injected virgin females. Pheromone glands of treated and untreated moths were extracted and analyzed by capillary gas chromatography for their most abundant pheromone components, (Z)-7-dodecenyl acetate and (Z)-9-tetradecenyl acetate, and the putative biosynthetic precursors hexadecanoate, (Z)-11-hexadecenoate, (Z)-9-tetradecenoate and (Z)-7-dodecenoate. Comparison of the amounts of the pheromone and precursor components in the three groups of females indicated that a neuroendocrine factor is involved in the regulation of the pheromone biosynthesis in C. chalcites. Lack of such a factor resulted in a marked decrease of the sex pheromone components as well as the three unsaturated putative biosynthetic precursors. However, no decrease was observed in the content of palmitoate, suggesting that the Δ11 desaturation step is affected by the neuroendocrine factor. Injection of head ganglia extracts into ligated females resulted in a recovery of unsaturated precursor and phermone content. Both male and female head ganglia were found to contain a sex pheromone biosynthesis regulatory factor. However, the stimulatory pattern of the factor from the two sexes was different, suggesting that the two factors are quantitatively and/or qualitatively distinct.