Synchronous Drosophila circadian pacemakers display nonsynchronous Ca 2+ rhythms in vivo

Layered versatility atop circadian clocks The circadian clock evolved to allow cells or organisms to anticipate changes in physiological requirements associated with Earth's 24-hour light/dark cycle. Some activities, however, need to occur out of phase with the core clock. Liang et al. imaged changes in intracellular concentration of Ca 2+ in populations of neurons in the fruit fly brain. Although the underlying clock was synchronous, the rhythms of Ca 2+ changes corresponded with distinct timing of activities associated with activity of the particular neuronal populations. Proper coordination of these distinct phases required expression of the neuropeptide pigment-dispersing factor and its receptor. Science , this issue p. 976