Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2004
Publication Date: 1/20/2005
Citation: Gries, R., Khaskin, G., Schaefer, P.W., Hahn, R., Gotoh, T., Gries, G. 2005. (7r,8s)-cis-7,8-epoxy-2-methyloctadec-17-ene: a novel trace component from the sex pheromone gland of gypsy moth, lymantria dispar. Journal of Chemical Ecology. 31:(1) 49-62 2005 Interpretive Summary: Because we theorized that the sex pheromone for gypsy moth was unusually simplistic, based on our work on other congeners, we thoroughly investigated the sex pheromones of both Asian and North American gypsy moth, Lymantria dispar, for the first time since Disparlure was first identified in 1970. We found a never-before-seen second component which we identified as (7R,8S)-cis-7,8-Epoxy-2-Methyloctadec-17-ene. In field trapping in northern Japan, we confirmed this to be a pheromone attractant itself but when added to the conventional (+)-disparlure, it did not enhance the overall effectiveness of (+)-disparlure as a trap lure. We believe this finding will have significant impact on our understanding of pheromone communication in gypsy moth and related species but we concede that (+)-disparlure alone remains the best lure for trapping male gypsy moths.
Technical Abstract: Considering the vast Eurasian distribution of gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae), the many subspecies, and their presence in many different lymantriid communities, we tested the hypothesis that L. dispar populations in eastern Asia employ one or more pheromone components in addition to the previously known single component pheromone (7R,8S)-cis-7,8-epoxy-2-methyloctadecane [ = (+)-disparlure]. Coupled gas chromatographic-electroantennographic detection (GC-EAD) and GC/GC-EAD analyses of gland extracts of female L. dispar sensu lato (including both Asian and North American gyspy moths) on four fused silica columns (DB-5, DB-23, DB-210, and SP-1000) revealed a new candidate pheromone component (CPC) that eluted just before (DB-5; DB-210) or after (DB-23, SP-1000) disparlure, and elicited strong antennal responses. Isolation of CPC by high-performance liquid chromatography, hydrogenation of the CPC-containing fraction, and GC-EAD of hydrogenated CPC, revealed a new antennal response with GC characteristics on all columns identical with those of disparlure, suggesting that CPC had the molecular skeleton of disparlure, with one or more double bonds. Of all conceivable monounsaturated cis-7,8-epoxy-2-methyloctadecenes, only cis-7,8 epoxy-2-methyloctadec-17-ene co-chromatographed with CPC on all analytical columns and elicited comparable antennal activity. In field experiments in Honshu (Japan) with enantioselectively synthesized compounds, (7R,8S)-cis-7,8-epoxy-2-methyloctadec-17-ene (7R8S-epo-2me-17-ene) itself attracted male L. dispar, but was less effective as a trap bait than (+)-disparlure, and failed to enhance attractiveness of (+)-disparlure. The antipode, (7S,8R)-cis-7,8-epoxy-2-methylyoctadec-17-ene, was not attractive by itself, and when added to (+)-disparlure and/or 7R8S-epo-2me-17-ene reduced their attractiveness. 7R8S-Epo-2me-17-ene may be atavistic with no discerning role in L. dispar from northern Honshu, but may enhance pheromone attractiveness or specificity in other L. dispar populations within their vast Eurasian distribution.