Effects of photoregime on the timing of male responses to sex pheromones in male Cnaphalocrocis medinalis (Lepidoptera: Crambidae)

Abstract

We examined the effect of moth age and photoregime on the timing of male response to sex pheromones in male Cnaphalocrocis medinalis. The responsiveness of males varied with age, increasing up to 3-days and then remaining constant to 7-days. In male responses to the pheromone throughout the scotophase under five different photoregimes, it was shown that the time to reach the maximal response level after lights-off was rather constant (ca. 4 h), regardless of the duration of the scotophase in a range from 6 to 18 h. The maximal response level in every case appeared to be maintained until the end of the scotophase. Furthermore, in the experiment involving Ϯ3 h shifts of lights-off or lights-on timing from the usual 15L:9D, the male responsiveness increased within 4 h after lights-off, and the maximal level extended throughout the remaining dark period. These results suggest that, at least under the present experimental conditions, only lights-off and lights-on cues are critical for the timing of the increase and decrease in responsiveness. No responsiveness was observed under light conditions, showing that light inhibits the responsiveness of males to sex pheromones.

Effects of photoregime on the diel rhythmicity of male responses to sex pheromones in Glyphodes perspectalis (Lepidoptera: Crambidae)

“…The window of male responsiveness was wide when the duration of the scotophase was long. Such a tendency of male responsiveness to sex pheromones was also reported in other moth species, e.g., Agrotis ipsilon (Gemeno and Haynes, 2000), T. ni (Linn et al, 1996), Platyptilia carduidactyla (Haynes and Birch, 1984), C. medinalis (Kawazu et al, 2003), and Herpetogramma phaeopteralis (Meagher et al, 2007). The wide window of male responsiveness will be maintained if the scotophase length increases with the season or the latitude where the males occur.…”

“…Experiments involving shifts in the time of lights-on or -off also supported the idea that the lights-off cue is critical for the expression and timing of the male response rhythm, the same as in other moth species, e.g., C. medinalis (Kawazu et al, 2003) and T. ni (Linn et al, 1996). With G. perspectalis, it is thought that male responsiveness is a function of the scotophase portion of the photoregime, and even though the lights-off cue is clearly important, both lights-on and -off cues are critical for sustaining the response rhythm.…”

“…In the cabbage looper moth Trichoplusia ni, studies on male responsiveness to sex pheromones suggested that the time to reach maximal response levels was relatively constant (2-3 h) after lights-off, regardless of the duration of the scotophase and the timing of lights-on or -off, and circadian oscillation is involved in male responsiveness (Linn et al, 1996). For the rice leaffolder moth, Cnaphalocrocis medinalis, only lights-on and -off cues are critical for the timing of the increase and decrease in male responsiveness to sex pheromones (Kawazu et al, 2003). Such reports show that the mechanism that controls male responsiveness to sex pheromones differs by species.…”

The Effect of Photoregime on the Calling Behavior of the Rice Leaf Folder Moth, Cnaphalocrocis medinalis (Lepidoptera: Crambidae)

“…3), suggesting that C. medinalis females use light-off to phaseset the circadian rhythm of their calling behavior. Only light-off and light-on cues are critical for the timing of the increase and decrease in male responsiveness to the sex pheromone in C. medinalis 13 . It is of interest that the female calling rhythm based on circadian oscillation is different from the male responsiveness to the sex pheromone that was affected by only light-off and light-on signals.…”