The Use of Mass Isotopomer Distribution Analysis to Quantify Synthetic Rates of Sex Pheromone in the Moth Heliothis virescens

Although there has been much investigation of the steps involved in sex pheromone biosynthesis in moths, little is known about the kinetics of biosynthesis in vivo , primarily because there are few techniques suitable for studying the small amounts of pheromone produced without perturbing a female moth’s normal physiology. In this paper, female Heliothis virescens moths fed on U- 13 C-glucose were subjected to mass isotopomer distribution analysis, enabling calculation of fractional (FSR) and absolute (ASR) synthetic rates of the main pheromone component, ( Z )-11-hexadecenal, at two different photoperiodic times: during the scotophase (when adults are sexually active) and during the photophase (when adults do not engage in mating behavior). FSRs differed substantially at the two times with, as expected, the greater rate occurring during the scotophase. After determining Z11-16:Ald pool sizes, ASR through the scotophase was calculated to be roughly 20 times greater than ASR in the photophase. These differences are consistent with the release/non-release of the pheromone biosynthesis-activating neuropeptide. This approach should facilitate determination of more quantitative measures of semiochemical production in moths and other sugar-feeding insects that synthesize semiochemicals from glycolytic metabolites.