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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
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Unusual response characteristics of pheromone-specific olfactory receptor neurons in the Asian corn borer moth, Ostrinia furnacalis

Takuma Takanashi1,2,*, Yukio Ishikawa2, Peter Anderson1, Yongping Huang3, Christer Löfstedt4, Sadahiro Tatsuki2 and Bill S. Hansson1,{dagger}

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


Figure 1
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  		Fig. 1. Electron micrographs of the male antenna in Ostrinia furnacalis. (A) Scanning micrograph of the basal flagellomer of the antenna. Large numbers of sensilla trichodea (green arrowheads) occur at the medial and lateral part of the ventral surface of the antenna. Basiconic sensillum (ba), coeloconic sensillum (co), auricillic sensillum (au), chaetic sensillum (yellow arrowhead) and styloconic sensillum (yellow arrow, behind s. trichodeum) are also visible. For morphological details of the sensilla, see text. Note the honeycomb-like surface sculpturing of the antennal cuticle. Scales occur on the dorsal surface. Bar, 20 µm. (B) Transmission micrograph of a basal transverse section through a sensillum trichodeum containing three unbranched outer dendritic segments (arrow) in the sensillum cavity. Honeycomb-like surface cuticle (arrowhead) surrounds the sensillum. This region lacks wall pores. Bar, 1 µm. (C) Middle section of an s. trichodeum containing three unbranched outer dendritic segments (arrow). Wall pores (arrowheads) were seen as less electron-dense areas in the wall cuticle. Note that the sensillum was cut obliquely and that inner structures of the outer dendritic segments were unclear because of incomplete fixation. Bar, 1 µm.

 

Figure 2
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  		Fig. 2. Single sensillum recordings from sensillum type 2 (see Fig. 3) containing two olfactory receptor neurons. In spikeamplitude histograms on the right-hand side of recordings, the neurons are distinguished by having different spike amplitudes for large spike amplitude (filled columns) and small spike amplitude (white columns). The figure shows responses to the two major pheromone components (E)-12- and (Z)-12-tetradecenyl acetates (E12- and Z12-14:OAc) at a 10 µg loading. The two neurons, characterized by a large (filled arrowhead) and small (open arrowhead) spike amplitude, respond to E12-14:OAc. The large spiking neuron is also stimulated by Z12-14:OAc. The correctness of the characterizations was corroborated by differential adaptation experiments (see Fig. 5).

 

Figure 3
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  		Fig. 3. Four different types of trichoid sensilla (1-4) characterized by their responses to E12- and Z12-14:OAc. Values showing the number of spikes per 0.5 s (means + s.e.m.) of receptor neurons with large and small spike amplitudes. (A) Responses of large and small spiking neurons housed within sensillum types 1-4 to E12-14:OAc (E12 large and E12 small) and to Z12-14:OAc (Z12 large and Z12 small) at dosages of 10 µg (N=71). *, significant difference between responses to E12- and Z12-14:OAc as tested by Mann-Whitney U-test (P<0.05); ns, not significant. (B) Dose-response curves were obtained from sensillum types 1-4 housing large and small spiking neurons responding to E12-14:OAc (E12 large and E12 small) and to Z12-14:OAc (Z12 large and Z12 small). The stimulus was loaded at 100 ng, 1 µg, 10 µg and 100 µg.

 

Figure 4
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  		Fig. 4. Three subtypes of trichoid sensilla (A-C) characterized by their responses to Z9-, E11- and Z11-14:OAc. Values showing number of spikes per 0.5 s (means + s.e.m.) of receptor neurons with large and medium spike amplitudes. (A) Responses of large and medium spiking neurons housed within sensillum subtype A, B and C to Z9-, E11- and Z11-14:OAc (Z9, E11 and Z11) at a stimulus loading of 10 µg (N=47). *, significant difference among responses to E12-, Z12- and Z9-14:OAc as tested by Friedman test (P<0.05); ns, not significant. (B) Dose-response curves of large and medium spiking neurons housed in medially situated sensilla (subtype A) and of medium spiking neurons in laterally situated sensilla (subtype C) stimulated by E11-14:OAc, Z11-14:OAc and Z9-14:OAc, respectively (Z9 large, Z9 medium, E11 large, E11 medium, Z11 large and Z11 medium). The stimulus was loaded at 100 ng, 1 µg, 10 µg and 100 µg. Values showing spike frequencies per 0.5 s (means + s.e.m.). No dose-response curve data were obtained for subtype B.

 

Figure 5
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  		Fig. 5. Responses of large and small spiking neurons during cross-adaptation experiments. (A) Typical adapted response to two 0.5 s stimuli of E12-14:OAc (10 µg) with an interval of 0.2 s, indicated as horizontal bars. (B) Histograms showing number of spikes per 0.1 s (means + s.e.m.) of large and small spiking neurons (large and small) in sensillum type 1 (N=5) before and after adaptation. Two stimuli [E12-14:OAc (E12) and Z12-14:OAc (Z12) in different stimulus combinations] (10 µg) were presented successively. Note how the activity of the second stimulation is equally affected by prestimulation of both the same and the opposite isomer.

 

Figure 6
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  		Fig. 6. Number of males (means + s.e.m.) captured by traps baited with different blends of E12-14:OAc and Z12-14:OAc (shown as % E12-14:OAc) during 19-29 May 1997 (N=4) (A). Number of males captured in traps baited with the optimal blend [36% E12-14:OAc (Ref)] as compared with those baited with the optimal blend plus 1% Z9-14:OAc (Z9) during 28 August-4 September 1997 (N=3) (B). The dosage used was 100 µg in each experiment. Bars with the same letters are not significantly different according to Tukey-Kramer's multiple-range test at the level of 5%. Data were transformed to log (x+1) prior to the statistical analysis. Ctrl, control traps.

 




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