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First published online December 1, 2006
Journal of Experimental Biology 209, 4946-4956 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02587
Unusual response characteristics of pheromone-specific olfactory receptor neurons in the Asian corn borer moth, Ostrinia furnacalis
1 Division of Chemical Ecology, Department of Crop Science, Swedish
University of Agricultural Sciences, SE-230 53 Alnarp, Sweden
2 Laboratory of Applied Entomology, Graduate School of Agricultural and Life
Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
3 Institute of Plant Physiology and Ecology, Shanghai Institutes for
Biological Sciences, Chinese Academy of Sciences, Shanghai 200032,
China
4 Department of Ecology, Lund University, SE-223 62 Lund, Sweden
* Author for correspondence at present address: Department of Forest Entomology, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8634, Japan (e-mail: takanasi{at}affrc.go.jp)
Accepted 5 October 2006
Male moth pheromone-detecting receptor neurons are known to be highly specific and very sensitive. We investigated physiological and behavioral responses to female sex pheromone components in male Ostrinia furnacalis moths (Lepidoptera: Crambidae). Using recordings from a cut-sensillum technique, trichoid sensilla could be grouped into four physiological types (1-4), according to the response of receptor neurons to the two major pheromone components, (E)-12- and (Z)-12-tetradecenyl acetate (E12- and Z12-14:OAc). These types could subsequently be characterized as four subtypes (A-D) depending on neural responses to pheromone components from various sister species of O. furnacalis, (Z)-9-, (E)-11- and (Z)-11-tetradecenyl acetate.
The peripheral pheromone detection system of O. furnacalis is
different to that of other moths. A large majority of the neurons investigated
responded to both of the two principal pheromone components. Dose-response and
cross-adaptation studies showed that olfactory receptor neurons with large
amplitude action potentials responded equally well to E12- and Z12-14:OAc in
sensillum types 1-3. Field experiments showed that O. furnacalis
males are sensitive to ratios of E12- and Z12-14:OAc and that
(Z)-9-tetradecenyl acetate acts as a behavioral antagonist. O.
furnacalis males thus display an unusual coding system for odors involved
in sexual communication, mainly built on less specific neurons, but still have
the ability to detect and respond to the correct female blend. We hypothesize
that the pheromone detection system of O. furnacalis consists of two
parts, where one is devoted to high sensitivity to 
12 isomers of
tetradecenyl acetate, E12- and Z12-14:OAc and the other to highly specific
responses to the E12- or Z12-14:OAc. The unusual feature is thus that a large
part of the system is devoted to sensitivity and only a minor part to
selectivity. This could be explained by the fact that no other moth species
are known to use E12- and/or Z12-14:OAc and that no strong selective pressure
to increase selectivity between the isomers has been determined.
Key words: olfaction, electrophysiology, single sensillum recording, Ostrinia nubilalis, sex pheromone communication, behavioral antagonist, field trapping, electron microscopy
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