Rhythm helps to keep corals going through the lonely low-point of the night, when their partner robs them blind.

To study the process the team used microarray analysis, taking samples every four hours under conditions of normal light/dark and total darkness.

Corals appear to have taken rhythm to an intense pitch, to the point where they have developed an internal 'clock' that ticks reliably even if the corals are no longer stimulated by external signals like the change from day to night or full moon to total dark - whereas many humans are adrift without a wristwatch.

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