Internal desynchronisation of bilaterally organised circadian oscillators in the visual system of insects

Abstract

MANY functions of multicellular organisms follow such a consistent daily periodicity, even in constant environmental conditions, that it has been natural to postulate control by a single internal clock. But some observations are explained only by the joint action of several circadian oscillators^1,2. Experimental confirmation of such a system has been obtained for several species^3,4. For example, two rhythms in an organism may have independent period lengths, even in steady state. This internal desynchronisation is thought to have been demonstrated when the phase difference between the two rhythms exceeds 360° (ref. 5). It has been described for humans¹ and non-human primates⁶. The possession of pairs of organs by bilaterally symmetrical metazoans suggests an anatomical basis for multioscillator organisation. So far, however, evidence has been based on surgical isolation of the oscillators of molluscs⁷ and crustaceans⁸, or indirectly on ablation experiments with insects^9–11. We have now obtained direct evidence with beetles, by demonstrating internal desynchronisation between the right and left sensitivity rhythms in the compound eyes, without surgical intervention.