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

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

Olfactory neuroethology of the Oriental fruit moth, Grapholita molesta (Busck)

The oriental fruit moth, Grapholita molesta, is one of the main pests of peach trees worldwide. It is conThe oriental fruit moth, Grapholita molesta, is one of the main pests of peach trees worldwide. Plant volatiles are a promising technique to attract G. molesta under mating disruption conditions. In my thesis I have characterized the response of olfactory receptor neurons (ORN) to pheromone and plant odors by means of single-sensillum electrophisiology. I then used this information to determine that a previously reported pheromone-plant synergism does not result from pheromone-plant interactions at the ORN level. I have compared several plant volatile blends previously tested in Australia and China, and have found that none of them attracted moths in the field, but they synergized pheromone responses in the laboratory. Finally, I investigated the role of plant blends and alcohols on the response to unnatural pheromone blend ratios or overdosed pheromone concentrations. With these studies we hopefully advanced on basic and applied aspects of the olfactory neuroethology of this species.Grapholita molesta es una de las principales plagas del melocotonero. Los volátiles de planta son una técnica prometedora para atraer G. molesta en condiciones de confusión sexual. En mi tesis he caracterizado la respuesta de las neuronas receptoras olfativas (ORN) a la feromona y volátiles de planta mediante registros de sensila única. Después determiné que el sinergismo entre volátiles de planta y feromona previamente publicado no ocurre a nivel de la ORN. Más adelante he comparado volátiles de planta que en estudios anteriores en China y en Australia habían dado buenos resultados pero en mi caso no hubo respuestas en campo, aunque en el túnel de vuelo sí que aumentaron la respuesta a la feromona. Finalmente he explorado el papel de volátiles de planta y alcoholes en la respuesta a mezclas subóptimas de feromona. Con estos resultados espero haber contribuido al conocimiento de la neuretología olfativa de esta plaga.Grapholita molesta és una de les principals plagues del presseguer. Els volàtils de planta són una tècnica prometedora per atreure G. molesta en condicions de confusió sexual. En la meva tesi he caracteritzat la resposta de les neurones receptores olfactòries (ORN) a la feromona i volàtils de planta mitjançant registres de sensila única. Després vaig determinar que el sinergismo entre volàtils de planta i feromona prèviament publicat no ocorre a nivell de la ORN. Més endavant he comparat volàtils de planta que en estudis anteriors a Xina i a Austràlia havien dau bons resultats però en el meu cas no va haver-hi respostes en camp, encara que en el túnel de vol sí que van augmentar la resposta a la feromona. Finalment he explorat el paper de volàtils de planta i alcohols en la resposta a mescles subóptimas de feromona. Amb aquests resultats espero haver contribuït al coneixement de la neuretología olfactòria d'aquesta plaga.trolled with sex pheromones (mating disrupton) and insecticide applications. Under mating disruption conditions it is difficult to monitor the pest and to evaluate the control methods. Plant volatiles are a promising technique to attract G. molesta under mating disruption conditions. In addition plant volatiles could attract females, while the sex pheromone only attracts males

Smoke, pheromone and kairomone olfactory receptor neurons in males and females of the pine sawyer Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae)

The response of antennal olfactory receptor neurons (ORNs) of Monochamus galloprovincialis to several odourants was tested using single sensillum electrophysiology. Behaviourally active pheromone, and kairomone (host and sympatric bark beetle pheromone) odours were tested alongside smoke compounds released by burnt wood that are potentially attractive to the insect. The antennae bore several types of sensilla. Two plate areas in the proximal and distal ends of each antennal segment were covered with basiconic sensilla that responded to the odour stimuli. Sensilla basiconica contained one or two cells of different spike amplitude. The 32 male and 38 female ORNs tested responded with excitations or inhibitions to the different plant odours. In general the response of male and female receptors was very similar so they were pooled to perform a cluster analysis on ORN responses. Six ORNs were clearly specialised for pheromone reception. Responses to kairomone and smoke odours were less specific than those of pheromone, but a group of 9 cells was clearly excited by smoke compounds (mainly eugenol and 4-methyl 2-methoxyphenol), a group of 8 cells was very responsive to a-pinene, b-pinene and cis-verbenol, and a group of 14 cells responded to a wider range of compounds. The rest of the cells(47%) were either non-responsive or slightly inhibited by smoke compounds. Dose–response curves were obtained for several compounds. Different compounds induced significantly different latencies and these appeared to be unrelated to their boiling point

1-octadecene, A Female Produced Aggregation Pheromone of the Coffee White Stem Borer (<i>Xylotrechus quadripes</i>)

Coffee white stem borer, Xylotrechus quadripes is a serious insect pest of coffee across the world. Pheromone traps baited with male produced 2-hydroxy- 3-decanone (2H3D) attracted females, and also males. Interestingly, a pair of males and females in a cage attracted more beetles compared to 2H3D traps. We hypothesized volatiles emitted from females are perceived by males. Volatiles from females were collected through the air entrainment method and identified 1-octadecene by using gas chromatography coupled with mass spectrometry. Release of 1-octadecene was female specific, however, both male and female antennae elicited responses in chromatography-electroantennography. Electroantennogram responses were dose-dependent in both sexes and were higher in the antennae of females. Combination of male pheromone component 2H3D, and female produced 1-octadecene at 1:2 ratio increased both male (0.69 ± 0.13; mean ± SEM in -mV) and female (0.98 ± 0.20) antennal responses. Responses to constant doses of 2H3D and increasing doses of 1-octadecene (1:4, 1:6, 1:8, 1:10) were not different from male pheromone alone. Beetle captures to male pheromone alone at 3 different doses (75, 150 and 300 mg) were not significantly different from a pair of live beetle traps. A blend of 2H3D and 1-octadecene at 1:2 ratio trapped more beetles (3.50 ± 0.65; mean ± SEM) over 2H3D alone (2.00 ± 0.82), overall, our experiments suggest 1-octadecene is an aggregation pheromone. Our results support the hypothesis that males use 1-octadecene in mate finding, and potential to use it for monitoring and mass trapping

1-octadecene, A Female Produced Aggregation Pheromone of the Coffee White Stem Borer (Xylotrechus quadripes)

Coffee white stem borer, Xylotrechus quadripes is a serious insect pest of coffee across the world. Pheromone traps baited with male produced 2-hydroxy- 3-decanone (2H3D) attracted females, and also males. Interestingly, a pair of males and females in a cage attracted more beetles compared to 2H3D traps. We hypothesized volatiles emitted from females are perceived by males. Volatiles from females were collected through the air entrainment method and identified 1-octadecene by using gas chromatography coupled with mass spectrometry. Release of 1-octadecene was female specific, however, both male and female antennae elicited responses in chromatography-electroantennography. Electroantennogram responses were dose-dependent in both sexes and were higher in the antennae of females. Combination of male pheromone component 2H3D, and female produced 1-octadecene at 1:2 ratio increased both male (0.69 &plusmn; 0.13; mean &plusmn; SEM in -mV) and female (0.98 &plusmn; 0.20) antennal responses. Responses to constant doses of 2H3D and increasing doses of 1-octadecene (1:4, 1:6, 1:8, 1:10) were not different from male pheromone alone. Beetle captures to male pheromone alone at 3 different doses (75, 150 and 300 mg) were not significantly different from a pair of live beetle traps. A blend of 2H3D and 1-octadecene at 1:2 ratio trapped more beetles (3.50 &plusmn; 0.65; mean &plusmn; SEM) over 2H3D alone (2.00 &plusmn; 0.82), overall, our experiments suggest 1-octadecene is an aggregation pheromone. Our results support the hypothesis that males use 1-octadecene in mate finding, and potential to use it for monitoring and mass trapping