Molecules and macromolecules involved in chemical communication of scarab beetles*

Abstract: Chemical communication involves the production and release of specific chemicals (pheromones and other semiochemicals) by the emitter, and the detection and olfactory pro-cessing of these signals leading to appropriate behavioral responses in the receiver. In con-trast to most of the scarab species investigated to date, the Japanese and Osaka beetles have the ability to detect the allospecific pheromone, which plays a pivotal role in the isolation mechanism between these two species. Each species produces a single enantiomer of japonil-ure [(Z)-5-(dec1-enyl)oxacyclopentan-2-one], but they have evolved the ability to detect both enantiomers, one as an attractant and the other as a behavioral antagonist (stop signal). There is growing evidence in the literature that the inordinate sensitivity and selectivity of the insect olfactory system is achieved by a combination of various olfactory-specific proteins, name-ly, odorant-binding proteins (OBPs), odorant receptors (ORs), and odorant-degrading enzymes. The relationship between the pheromone structures and the primary sequences of the proteins suggest that OBPs play a part in the selectivity of the olfactory system in scarab beetles by “filtering ” chemical signals during the early olfactory processing (perireceptor events). Nevertheless, it is unlikely that pheromone-binding proteins are “chiral filters ” as th