Male-Produced Sex Pheromone of the Carrion Beetles, Oxelytrum discicolle and its Attraction to Food Sources

Abstract

Carrion beetles are part of the great diversity of insects collected on cadavers. In Brazil, beetles of the genus Oxelytrum have great forensic importance in post mortem interval (PMI) estimation. We investigated the system of chemical communication in the attraction of these necrophagous beetles. Gas chromatographic analysis (GC) of female and male aeration extracts revealed the presence of two male-specific compounds, produced in a ratio of 94:6. Bioassays showed that the combination of male produced volatiles and the odor of a food source (carcass volatiles) were attractive to females. Mass and infrared spectral analyses of the male-specific compounds suggested that they were both unsaturated hydrocarbons. Several micro-derivatizations were carried out with the natural products, and the target structures were identified as (Z)-1,8-heptadecadiene (major) and 1-heptadecene (minor). The structure of the minor component was assigned by co-injection with a commercial standard. A seven-step synthesis was developed to synthesize (Z)-1,8-heptadiene, which co-eluted with the major natural product on three different GC stationary phases. Y-tube olfactometer assays showed that the mixture of synthetic standards in the naturally occurring proportion was slightly attractive to females. The results contribute both to the understanding of the chemical ecology of O. discicolle and to its potential to improve the accuracy of PMI estimation.