Key internal clock genes control daily and tidal rhythms in the marine crustacean Parhyale hawaiensis

Marine organisms exhibit 12.4-h rhythms of gene expression, physiology, and behavior synchronized by tidal cues.

• The core circadian genes PhCry2, PhPer, and PhClk are necessary for both circadian and circatidal behaviors in P. hawaiensis.
• All four core circadian genes, including BMAL1, are critical for maintaining 24-h mRNA oscillations in circadian brain neurons.
• These genes also support 12.4-h mRNA rhythms specifically in circatidal neurons.
• PhCLK appears to independently repress PhPer expression in circatidal neurons, separate from PhBMAL1's influence.
• The study indicates that circadian and circatidal clocks share core components, but their regulatory mechanisms differ.

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