Numerous insect species living in temperate regions survive adverse conditions, such as winter, in a state of developmental arrest. The most reliable cue for anticipating seasonal changes is the day-to-night ratio, the photoperiod. The molecular mechanism of the photoperiodic timer in insects is mostly unclear. Multiple pieces of evidence suggest the involvement of circadian clock genes, however, their role might be independent of their well-established role in the daily oscillation of the circadian clock. Furthermore, reproductive diapause is preferentially studied in females, whereas males are usually used for circadian clock research. Given the idiosyncrasies of male and female physiology, we decided to test male reproductive diapause in a strongly photoperiodic species, the linden bug Pyrrhocoris apterus. The data indicate that reproduction is not under circadian control, whereas the photoperiod strongly determines males' mating capacity. Clock mutants in pigment dispersing factor and cryptochrome-m genes are reproductive even in short photoperiod. Thus, we provide additional evidence of the participation of circadian clock genes in the photoperiodic time measurement in insects.

• Keywords
• Circadian clock, Cryptochrome, Photoperiodism, Pigment dispersing factor, Reproductive diapause,
• MeSH
• Circadian Clocks * genetics   physiology   MeSH
• Circadian Rhythm physiology   genetics   MeSH
• Diapause, Insect genetics   physiology   MeSH
• Photoperiod * MeSH
• Heteroptera * genetics   physiology   MeSH
• Insect Proteins genetics   metabolism   MeSH
• Cryptochromes * genetics   metabolism   MeSH
• Mutation * MeSH
• Reproduction physiology   genetics   MeSH
• Sexual Behavior, Animal physiology   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Insect Proteins MeSH
• Cryptochromes * MeSH