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 because 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 ecological roles. In males 63% of the ORNs were tuned specifically to the major and minor female sex pheromone components, and 4% to the plant volatile blend, while the remaining 33% showed unspecific responses. 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.