Selectivity and neuroendocrine regulation of the precursor uptake by pheromone glands from hemolymph in geometrid female moths, which secrete epoxyalkenyl sex pheromones

Abstract

Macrolepidopteran female moths in families such as Geometridae produce epoxyalkenyl sex pheromones, which are biosynthesized via epoxidation of polyunsaturated hydrocarbons in their pheromone glands. The precursors, however, are expected to be produced outside of the pheromone glands, probably in oenocytes or in the fat body, and transported to the glands via hemolymph. Based on these facts, the selectivity of the epoxidation substrates and of the precursor uptake by pheromone glands was examined with two geometrid species, Hemerophila artilineata and Ascotis selenaria cretacea, using binary mixtures of deuterated precursors and their analogs, which were topically applied to the pheromone glands or injected into the abdomen. GC–MS measurements of pheromone extracts showed equal epoxidation of two polyenes, indicating a low selectivity for both processes, while the epoxidation proceeded at only one double bond specific to each species. This result makes it possible to conclude that the formation of species-specific epoxyalkenyl pheromones results from the rigid formation of polyunsaturated precursors and their epoxidation at a fixed position. Next, the neuroendocrine regulation of these processes was studied with in vivo and in vitro experiments using decapitated females. The epoxy pheromones disappeared completely within 36 h of decapitation, and epoxidation of the injected precursors was not detected in the decapitated females, which restarted the reaction by treatment with a pheromone biosynthesis-activating neuropeptide (PBAN). The precursors topically applied to glands of the decapitated females, however, were converted into epoxy pheromones without PBAN, indicating that this neuropeptide hormone accelerated the precursor uptake by pheromone glands but not the epoxidation already underway in the glands.