Insect circadian clocks: is it all in their heads?

Circadian rhythms are ubiquitous in living organisms, synchronizing life functions at the biochemical, physiological, and behavioral levels. The rhythm-generating mechanisms, collectively known as circadian clocks, are not fully understood in any organism. Research in the fruit fly Drosophila has led to the identification of several clock genes that are involved in the function of the brain-centered clock, which controls behavioral rhythms of adult flies. With the use of clock genes as markers, putative circadian clocks were mapped in the fly peripheral organs and shown to be independent from clocks located in the brain. A homologue of fruit fly period gene has been identified in moths and other insects, allowing investigations of this gene's role in known insect rhythms. This approach may increase our understanding of how circadian clocks are organized into the circadian system that orchestrates temporal integration of life processess in insects. (C) 1999 Elsevier Science Ltd. All rights reserved.