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Neurocircuitry of Circadian Clocks

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Insect Chronobiology

Part of the book series: Entomology Monographs ((ENTMON))


Classical studies using several insect species have demonstrated that the principal circadian clock cells that generate circadian oscillations and control behavioral rhythms are located in a specific brain region. The discovery of a clock gene, period (per), in Drosophila melanogaster further facilitated the identification of specific cells by labeling gene expression. Since most of the per-expressing brain neurons display circadian molecular oscillations in the levels of per mRNA and its protein expression, they have conventionally been defined as “circadian clock neurons.” In Drosophila, approximately 150 neurons (out of 200,000 brain neurons) have been identified as clock neurons. However, elucidating the role of clock neurons, even with the Drosophila model, has been a major challenge. In 1995, it was discovered that 16 clock neurons expressed a neuropeptide, pigment-dispersing factor (PDF), the most important neurotransmitter for the insect circadian clock. This was where Drosophila genetics and neuroscience met in chronobiology, leading to a significant development in the functional analysis of clock neurons in Drosophila and the identification of clock neurons in nonmodel insect species. This chapter will summarize the latest findings of the clock neuron network in Drosophila and other insect species.

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We thank Misako Yoshii for figure drawing and Charlotte Helfrich-Förster for comments on figures. This work was supported by JSPS KAKENHI (19H03265).

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Correspondence to Taishi Yoshii .

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© 2023 The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

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Yoshii, T., Fukuda, A. (2023). Neurocircuitry of Circadian Clocks. In: Numata, H., Tomioka, K. (eds) Insect Chronobiology. Entomology Monographs. Springer, Singapore.

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