Tiny Four-Cell Hofbauer-Buchner Eyelets in Drosophila Are Hard-Wired to Clock Neuron Network in Brain Responsible for Regulating Rest/Activity Behavior in Response to Light

Fruit flies' activity peaks especially in the morning and late afternoon. The insects extend their midday rest period on long summer days. Researchers from the University of Würzburg in Germany have now found out what triggers this behavior. A miniature pair of eyelets also discovered in Würzburg in the late 80s plays a crucial role in this context. In 1989, the Würzburg biologists Alois Hofbauer and Erich Buchner reported a then surprising finding in the journal "Naturwissenschaften.” The scientists had identified a new pair of eyelets in Drosophila unknown until then. The fruit fly was considered an important model organism for zoologists and geneticists even then, with scores of scientists showing an interest in the tiny insect. But they had all failed to detect the additional eyes – no wonder given their microscopic size: each eyelet consists of just four photoreceptor cells. In spite of this, the Hofbauer-Buchner eyelets seem to play a major role in the life of Drosophila. A study conducted by scientists from the University of Würzburg with colleagues from the University of Michigan and the University of Bristol has come to this conclusion. Drosophila's activity peaks in the morning and in the late afternoon and they rest during the hottest time of the day. The tiny sensory organs (the two microscopic four-celled eyelets) evidently influence when this midday rest ends. "On long summer days, they delay the onset of the afternoon activity phase," explains Professor Charlotte Helfrich-Förster from the University of Würzburg's Biocenter. The scientist has studied drosophila's circadian rhythms for years.
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