Regulation of opsin and circadian clock genes on mate-finding behavior of the day-flying red moth, (Walker).

First, significantly higher mate-finding success was found under light condition than under constant darkness condition in , a typical diurnal moth. We speculate that mate-finding behavior in may be influenced by the light-sensitive opsin genes (), () and (), which are potentially regulated by both light-cues and endogenous circadian rhythms. Second, the circadian clock genes (), (), (), (), (), (), (), (), and () were identified in . Third, circadian rhythms in the relative expression levels of opsin and circadian clock genes were demonstrated via quantitative real-time PCR analysis, with peak expression coinciding with the mate-finding peak. Notably, the relative expression of in males was significantly higher than that in females at the mate-finding peaks Zeitgeber time (ZT) 8 and ZT 10 under light, while the expression of the opsin gene showed a similar pattern at ZT 10 under light. Additionally, the expression of the clock gene was significantly higher in males than in females at ZT 8 and ZT 10 under light, while , , and exhibited similar male-biased expression patterns at ZT 10 under light. Conversely, and expression was significantly higher in females than in male at ZT 8 under light. In conclusion, sex differences were detected in the expression of opsin and circadian clock genes, which indicated that light-mediated regulation of these genes may contribute to the daytime mate-finding behavior of .