Determination of the Absolute Configuration of Female-Produced Contact Sex Pheromone Components of the Longhorned Beetle, Neoclytus acuminatus acuminatus (F)

Abstract

Cuticular hydrocarbons play important roles in contact chemical communication in insects. Many of these compounds are methyl-branched hydrocarbons with one or more chiral centers, which can exist in two or more stereoisomeric forms. Although the importance of chirality for the volatile semiochemicals that insects use for long-range communication is well established, almost nothing is known about the role of chirality in insect contact chemoreception. Here, we used reverse phase high performance liquid chromatography (RP-HPLC) and digital polarimetry to isolate and determine the absolute configuration of a component of the female-produced contact sex pheromone of the cerambycid beetle, Neoclytus acuminatus acuminatus (F.). The pheromone consists of 7-methylpentacosane (7-MeC25), 7-methylheptacosane (7-MeC27), and 9-methylheptacosane (9-MeC27). The absolute configuration of the most abundant pheromone component, 7-MeC25, was found to be (R). We then utilized enantiomerically pure synthetic pheromone components to test the hypothesis that males would respond more strongly to (R)- than to (S)-enantiomers of the three pheromone components. We also tested blends of (R)-7-MeC27, the most bioactive component, with the (S)-enantiomers of the minor components and vice versa to determine if unnatural stereoisomers might decrease behavioral responses. Males responded most strongly to solvent-washed females treated with the blend of (R)-pheromone components, and to a lesser extent to (R)-7-MeC27 alone. A blend of (R)-7-MeC27 with the (S)-minor components elicited an intermediate response. Together, these findings suggest that the insects can discriminate the absolute configuration of the major and minor pheromone components, and that the configuration of all three components is likely to be (R).

Similar Is Not the Same – Mate Recognition in a Parasitoid Wasp

“…Dead females treated with a blend of (S)-5-methylheptacosane and (5R,17S)-5,17-dimethylheptacosane were more attractive to males than untreated dead females, while a treatment with the mixture of (R)-5-methylheptacosane and (5R,17R)-5,17dimethylheptacosane was repellent in a similar way as dead conspecific males were. Apart from the work on O. kuvanae, several other studies indicate that chiral methyl-branched CHCs are not only produced, but also perceived enantioselectively (Bello et al, 2015;Hughes et al, 2015;Sharma et al, 2015;de Narbonne et al, 2016). This may also apply for T. zealandicus.…”

“…In other cases, however, sex pheromone function is not quite as straight forward. Sex specific key compounds may trigger a full response only when presented together with the remaining CHC background or other compounds (Kühbandner et al, 2012; see discussion in Hughes et al, 2015). Additionally, the CHC profiles of potential mating partners may be detected as a whole, as is indicated when their sex pheromone function can be disturbed by changes in the overall composition or in the relative amounts of single compounds (Kühbandner et al, 2013;Würf et al, 2020).…”

Comparative morphometric and chemical analyses of phenotypes of two invasive ambrosia beetles (Euwallacea spp.) in the United States

“…The factors, whether genetic or nongenetic, which influence the differences between the cuticular hydrocarbon profiles of PSHB and TSHB remain to be understood, but this relatively simple chemical procedure will provide a means of separating small samples of the 2 species for future research on their invasion biology. The differences in steroisomeric forms of the methyl-branched cuticular hydrocarbons between PSHB and TSHB and their bioactivity remain to be understood, and these hypothetical differences may further distinguish these 2 species (Hughes et al, 2015;Ruther, 2015).…”

The evolution of sexually dimorphic cuticular hydrocarbons in blowflies (Diptera: Calliphoridae)

“…CHCs are essential to the survival of terrestrial insects, forming a hydrophobic layer that can adapt to environmental changes to prevent cuticular water loss (Chung & Carroll, 2015; Sprenger, Burkert, Abou, Federle, & Menzel, 2018; Stinziano, Sové, Rundle, & Sinclair, 2015). CHCs have also been adapted as close‐range pheromones, facilitating species recognition and sexual attraction in a wide range of insects (Curtis et al., 2013; Ferveur, 2005; Hughes, Bello, Millar, & Ginzel, 2015; Ingleby, 2015). Thus, CHCs provide a classic example of a dual trait, as they are a salient target for selection on: (a) their waterproofing capabilities and (b) their communication function in inter‐ and intra‐specific interactions (Chung & Carroll, 2015).…”