A closer look at sex pheromone autodetection in the Oriental fruit moth

Abstract

Female moths emit sex pheromone to attracts males, and although they are not attracted to their own sex pheromone, they appear to detect it as it affects their behavior. In order to elucidate the mechanism of pheromone “autodetection” we compared responses of olfactory receptor neurons (ORNs) of male and female Grapholita molesta, a species with reported pheromone autodetection. Two concentrations of the major (Z8-12:Ac) and minor (E8-12:Ac) sex pheromone components, a plant-volatile blend containing methyl salicylate, terpinyl acetate and (E)-β-farnesene, and the male-produced hair-pencil (i.e., courtship) pheromone (ethyl trans-cinnamate) were tested in 45 male and 305 female ORNs. Hierarchical cluster analysis showed radically different peripheral olfactory systems between sexes that could be linked to their specific roles. In males 63% of the ORNs were tuned specifically to the major or minor female sex pheromone components, and 4% to the plant volatile blend, while the remaining 33% showed unspecific responses to the stimulus panel. In females 3% of the ORNs were specifically tuned to the male hair-pencil pheromone, 6% to the plant volatile blend, 91% were unspecific, and no ORN was tuned their own sex pheromone components. The lack of sex pheromone-specific ORNs in females suggests that they are not able to discriminate pheromone blends, and thus pheromone autodetection is unlikely in this species. We discuss our results in the context of the methodological limitations inherent to odor stimulation studies.

Pheromone and Host Plant Odor Detection in Eastern Spruce Budworm, Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae)

“…Amounts of impurities in test stimuli and unspecific responses associated with high dosage may also obscure true ligand-receptor relationships [62][63][64]. Research on G. molesta concluded that females did not respond to female-produced sex pheromones and furthermore suggest that female autodetection observed in other species may be largely artefacts of high dosages or impurities in stimuli [56]. However, in this study most of the odorants selected had relatively similar size, vapor pressures and high purity.…”

“…In the tortricid moth, C. pomonella, cross-adaption studies of the codlemone type receptor showed a reduced response to all codlemone isomers and E8, E10-12:Ac a short time (5 s) after stimulation with E8,E10-12:OH at a high dose of 10 µg and less adaptation when stimulated with the same dose of E8,Z10-12:OH [55]. Another study on Heliothis subflexa Guenée (Lepidoptera: Noctuidae) and Heliothis virescens F. (Lepidoptera: Noctuidae) to components of their sex pheromones confirmed the presence of two ORNs usually having different spike sizes and tuned to different components ((Z)-11-16Ac and (Z)-11-16:OH) [56]. However, the same study showed that in H. subflexa, (Z)-11-16Ac tuned neuron also elicited responses to (Z)-9-14Ald with nearly equivalent sensitivity [57].…”

European grapevine moth, Lobesia botrana Part I: Biology and ecology

“…This may affect their longevity and reproductive potential as repeated calling is costly (Harari et al 2011). Alternatively, since females are relatively anosmic to their own sex pheromone, especially towards the minor pheromone components (Vitagliano et al 2005;Pérez-Aparicio et al 2019), the observed response to mating disruption concentrations of sex pheromone may not be due to a pheromone autodetection sensu stricto (Holdcraft et al 2016) but to the consequence of misleading odour stimulation (Pérez-Aparicio et al 2022). In either case, the implications of changes in female behaviour under mating disruption deserve further study (Pérez-Aparicio et al 2022).…”