Abstract
Long-range sex pheromones are generally considered to be a main cue for mate recognition in the order Hymenoptera. Although considerable attention has been given to the identification of semiochemicals in the superfamily Chalcidoidea, which comprises 19 families, no study has identified active components in a field bioassay. We herein report the sensitive and selective pheromone communication system of the Korean apricot wasp, Eurytoma maslovskii (Eurytomidae), whose larvae feed on Prunus mume seeds. Using gas chromatography coupled with electroantennographic detection (GC-EAD) and mass spectrometry (GC-MS), we detected 2,10-dimethyldodecyl propionate and 2,8-dimethyldecyl propionate in thoracic extracts of female E. maslovskii at a ratio of 8:2 as the active pheromone components. Field experiments showed that the attractive effect of the two compounds is highly enantioselective. Racemic 2,10-dimethyldodecyl propionate and 2,8-dimethyldecyl propionate were not attractive to E. maslovskii males. In bioassays with single enantiomers, the (2 S,10 R)-enantiomer was highly attractive to male wasps, and the (2 S,8 S)-enantiomer was also attractive, although to a lesser degree. No synergistic effect between (2 S,10 R)- and (2 S,8 S)-enantiomers was identified, and the (2 S,10 R)-enantiomer alone caught significantly more males than the natural pheromone extracts. The addition of other enantiomers to the (2 S,10 R)-isomer significantly decreased the attraction of conspecific males. In addition, a very low dose of synthetic pheromone attracted conspecific males, showing that both female signaling and male response traits may have evolved to contribute to species-specific sexual communication in this species.
Highlights
Long-range sex pheromones are generally considered to be a main cue for mate recognition in the order Hymenoptera
We demonstrate that female E. maslovskii produce 2,10-dimethyldodecyl propionate and 2,8-dimethyldecyl propionate at very low levels and that conspecific males selectively respond to (2S,10R)- and (2S,8S)-enantiomers in the field
The gas chromatography coupled with electroantennographic detection (GC-EAD) analysis showed that male wasp antennae responded consistently to only two compounds in the 5% fraction of thoracic extracts obtained from virgin females (Fig. 2, peaks A and B)
Summary
Considerable attention has been given to the identification of semiochemicals in the superfamily Chalcidoidea, which comprises 19 families, no study has identified active components in a field bioassay. Considerable attention has been given to the identification of semiochemicals in hymenopteran species, the female long-range sex pheromones of only five species from the suborder Symphyta and six species from the suborder Apocrita have been completely characterized in field bioassays[2]. Evidence related to long-range sex pheromones has been found for chalcidoid species from Aphelinidae[15], Chalcididae[16], Pteromalidae[17], Eulophidae[18], Eurytomidae[19,20], and Trichogrammatidae[21] None of these studies identified the active components using field bioassays. We demonstrate that female E. maslovskii produce 2,10-dimethyldodecyl propionate and 2,8-dimethyldecyl propionate at very low levels and that conspecific males selectively respond to (2S,10R)- and (2S,8S)-enantiomers in the field
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