Daily and tidal rhythms of clock gene activity in the brains of two intertidal crustaceans

Around 60 clusters of putative 'clock' cells were identified in the brains of intertidal crustaceans E. pulchra and P. hawaiensis.

• Circadian clock genes per and cry2 showed daily expression rhythms in specific cell groups of E. pulchra under light:dark cycles.
• The timeless gene exhibited 12-hour rhythmic expression in different cell groups, indicating a possible circatidal rhythm.
• Laboratory-reared P. hawaiensis displayed circadian expression of per and cry2 in some cells after exposure to tidal agitation.
• Dorsal-lateral cells in P. hawaiensis showed strong 12-hour rhythms of per and cry2, aligned with tidal agitation rather than light cycles.
• In P. hawaiensis without tidal agitation, daily rhythms of per and cry2 were present in some cells, while dorsal-lateral cells lacked rhythmicity.

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