We investigated the relationship between rhythms occurring at different time-scales, namely circadian and ultradian rhythms. Furthermore, we examined the potential role of the period (per) gene, a known clock gene initially isolated in Drosophila, for regulating these rhythms in the wild-type cricket, Teleogryllus oceanicus . Here we report a positive correlation between circadian and ultradian rhythms in crickets. Thus, crickets with a slow endogenous circadian rhythm also have a slow ultradian rhythm, and conversely, animals with a fast endogenous circadian rhythm have a fast ultradian rhythm. In addition to this correlation, we observed PER-like immunoreactivity in the regions of the cricket nervous system involved in regulating these rhythms, namely the brain, in particular the optic lobes, and the meso- and metathoracic ganglia. We thus conclude that different time-scale rhythms may be regulated by a common setting element, a role potentially played by the per gene.

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