Does the clock stop ticking? Ontogeny of the circadian clock in Sarcophaga crassipalpis

Many insects avoid the harsh environmental conditions of winter by entering diapause, a state of dormancy, in response to the short days of early autumn. The insect circadian clock that regulates daily behaviors may be what determines whether or not diapause occurs later in the life of an insect. The circadian clock is composed of several genes, including period, timeless, cryptochrome 1, cycle, and clock, whose transcripts oscillate in response to the daily light: dark cycle. These genes may also respond to temperature, but the relationship between light entrainment and temperature entrainment is unclear. Also unclear is the exact relationship between the circadian clock, different developmental stages, and diapause. Using quantitative Real Time PCR, gene expression of several clock genes was measured to determine how the clock cycles throughout the life of the flesh fly Sarcophaga crassipalpis under diapause inducing or averting conditions. The effect of temperature and light cycles on eclosion rhythm was also examined. From this data I hypothesize an ontogeny of the circadian clock. I hypothesize that clock genes oscillate in larvae, then clock gene oscillations dampen and cease during early pupation, before diapause. Shortly before adult eclosion the clock becomes temperature sensitive. After eclosion the clock is light sensitive and circadian oscillations have resumed. Circadian gene expression changes not only throughout the day but also throughout development.