In the first mode, occurring in some families such as pyralid and saturniid moths, the OSNs tuned to different pheromone components are co-compartmentalized in the same sensillum. At present, two modes of distribution have been described. The peripheral coding might be affected by the way the OSNs tuned to different components of the pheromone blend are distributed in functional types of trichoid sensilla. Many studies have demonstrated the specificity of response of insect OSNs to individual pheromone components but it is still unclear how insects are able to determine specific ratios of these components based on peripheral coding. An enlarged glomerular neuropil structure called the macroglomerular complex (MGC) is responsible for processing sex pheromones in the male AL –. In the AL, the OSNs expressing the same odor receptor converge onto a single glomerulus. OSNs housed in trichoid sensilla of male moths usually detect sex pheromones, as reported in many Lepidopteran species –. The OSNs are responsible for encoding the quality, quantity and temporal changes of the olfactory stimulus. Odorant molecules are first detected by receptors in the dendritic membrane of specialized olfactory sensory neurons (OSNs) housed in olfactory sensilla on the antenna, from which odor information is relayed to the antennal lobe (AL). How male moths discriminate sex pheromones released and successfully locate their mates is an active area of research –. Differences in blend ratios often underlie sexual isolation among sympatric species that may frequently encounter each other without mating. Therefore male moths locate their mates based not only on the identity of pheromone components, but also on their ratios. In closely related moth species, pheromone blends often consist of the same compounds but in different ratios. Male moths are attracted to females by conspecific sex pheromones, usually blends of two or more components released by females in defined ratios. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. KSCX2-EW-N-005), and National Science Fund for Distinguished Young Scholars (Grant No. 31130050), National Basic Research Program of China (Grant No.2012CB114105), the Chinese Academy of Sciences innovation program (Grant No. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: This work was supported by the National Natural Science Foundation of China (Grant No. Received: JanuAccepted: JPublished: July 23, 2013Ĭopyright: © 2013 Wu et al. assulta, eventually producing different behaviors.Ĭitation: Wu H, Hou C, Huang L-Q, Yan F-S, Wang C-Z (2013) Peripheral Coding of Sex Pheromone Blends with Reverse Ratios in Two Helicoverpa Species. Such information was then accurately reported to ALs of H. These results demonstrate that the binary pheromone blends were precisely coded by the firing frequency of individual OSNs tuned to Z11–16: Ald or Z9–16: Ald, as well as their population sizes. The calcium activities in the AL reflected the peripheral input signals of the binary pheromone mixtures and correlated with the behavioral output. armigera, while 5.4% and 8.6% of AL in H. At the dosage of 10 µg, Z11–16: Ald and Z9–16: Ald evoked calcium activity in 8.5% and 3.0% of the AL surface in H. armigera had the same sensitivity but lower efficacy than those in H. armigera exhibited higher sensitivity and efficacy than those in H. The ratios of OSNs responding to Z11–16:Ald and Z9–16:Ald OSNs were 100∶28.9 and 21.9∶100 in H. Z11–16: Ald and Z9–16: Ald were recognized by two populations of olfactory sensory neurons (OSNs) in different trichoid sensilla on antennae of both species. Using wind tunnel tests, single sensillum recording and in vivo calcium imaging, we comparatively studied behavioral responses and physiological activities at the level of antennal sensilla and antennal lobe (AL) in males of the two species to blends of the two pheromone components in different ratios (100∶0, 97∶3, 50∶50, 7∶93, 0∶100). Two sympatric species, Helicoverpa armigera and Helicoverpa assulta, use ( Z)-11-hexadecenal (Z11–16: Ald) and ( Z)-9-hexadecenal (Z9–16: Ald) as essential sex pheromone components but in very different ratios, 97∶3 and 7∶93 respectively. The relative proportions of components in a pheromone blend play a major role in sexual recognition in moths.
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