Figure 3

Bicuculline significantly affects pheromone-mediated navigation behavior. (a-c) Behavioral measurements on unoperated (gold), saline-injected (cyan) and bicuculline-injected (red) moths in a wind tunnel supplied with (a) pheromone or (b) solvent control (cyclohexane). Neither bicuculline nor saline injection affected a moth's ability to be motivated to fly (wing-fanning) or make upwind progress. A significantly lower percentage of bicuculline-injected moths (n = 12) displayed close hover, source contact and abdomen curl, compared with the unoperated (n = 10) and saline-injected (n = 15) groups (G test: p < 0.05). Under cyclohexane, all moths showed wing-fanning behavior, but only 30–50% of moths in each group (n = 10, 6, 9 for unoperated, saline-injected and bicuculline-injected, respectively) progressed upwind and an even lower percentage displayed close hover and source contact. None of the animals that came close to the source displayed abdomen curl. (c) The effects of bicuculline on close hover, source contact and abdomen curl shown in (a) were reversed after recovery for at least 2 h in a dark environmental chamber (n = 8, 7, 9 for unoperated, saline-injected and bicuculline-injected, respectively). Different letters within a behavioral category denote statistical significance (G test:p <0.05). (d-i) Flight-track analysis on unoperated (d, g), saline-injected (e, h) and bicuculline-injected (f, i) moths with pheromone or solvent control in the wind tunnel. (d, e) Using pheromone as the odor source, the unoperated and saline-injected moths flew directly toward the odor source, thus resulting in approximately straight flight tracks (top), centrally distributed transit probability (middle panels) and track-angle distribution histograms (bottom panels) with a prominent peak at zero degrees (mean ± SEM). The central distribution of transit probability is further demonstrated with a summed bar graph (along the wind direction) located to the right of the pseudocolor plots, showing a single peak at the center. (f) Bicuculline-injected moths, on the other hand, markedly diminished the central peak as well as the tracking frequency peak at zero degree track angle. (g-i) Replacing the pheromone with solvent control (cyclohexane) in the wind tunnel resulted in unanimous 'looping' flight tracks in all three treatment groups, reflecting an engagement of cross-wind casting in these moths, which is also shown in the randomly distributed transit probability of occupancy as well as in the bimodal distribution of track angle histograms.