Chemical communication in heliothine moths

The chemical and temporal features of the sex-pheromone emitted by Heliothis virescens females are encoded by a diverse array of output pathways from the male-specific macroglomerular complex (MGC) in the antennal lobe. Most output neurons (29 out of 32) were activated by antennal stimulation with the principal component of the sex-pheromone blend of this species, (Z)-11-hexadecenal. Six neurons were excited solely by this component, 8 neurons also responded to the second essential blend component, (Z)-9-tetradecenal, and 14 neurons displayed equivalent responses to the two. Many neurons also effectively encoded the onset and duration of the stimulus. In one additional neuron, a prolonged excitatory response (synergism) was evoked only by the blend of the two components, indicating that some MGC neurons function as blend detectors.In contrast to the situation in Helicoverpa zea, none of the MGC neurons in H. virescens responded selectively to (Z)-9-tetradecenal, suggesting that these two noctuid species employ different neural strategies to encode information about their respective pheromone blends.Three MGC-output neurons responded selectively to (Z)-11-hexadecenyl acetate, an odorant released by some sympatric species that disrupts normal upwind flight to pheromones. Thus, changes in the attractant and deterrent chemical signals, as well as the physical features of these odor plumes, are encoded in the MGC across a diverse parallel array of output pathways to the protocerebrum.Abbreviations AL antennal lobe - AN antennal nerve - 16:AL hexadecanal - MGC macroglomerular complex - 14:AL tetradecanal - Z11-16:AL (Z) 11-hexadecenal - Z11-16:AC (Z) 11-hexadecenyl acetate - Z9-14:AL (Z) 9-tetradecenal - Z9-14:FO (Z) 9-tetradecenyl formate