Tick Tock: Marine Animals With at Least Two Internal Clocks

Sep. 26, 2013 — Animals living in marine environments keep to their schedules with the aid of multiple independent -- and, in at least some cases, interacting -- internal clocks. The findings, presented by two research groups in papers appearing in the Cell Press journals Current Biology and Cell Reportson September 26, suggest that multiple clocks -- not just the familiar, 24-hour circadian clock -- might even be standard operating equipment in animals.

"The discovery of the circadian clock mechanisms in various terrestrial species from fungi to humans was a major breakthrough for biology," says Charalambos Kyriacou of the University of Leicester, who led one of the two studies on an inter-tidal crustacean known as a speckled sea louse. "The identification of the tidal clock as a largely separate mechanism now presents us with an exciting new perspective on how coastal organisms define biological time."

In the second study, Kristin Tessmar-Raible from the Max F. Perutz Laboratories at the University of Vienna and colleagues describe interactions between the familiar 24-hour circadian clock and a circalunar clock in a marine bristle worm.

"Our results suggest that the bristle worm possesses independent, endogenous monthly and daily body clocks that interact," Tessmar-Raible says. "Taking this together with previous and other recent reports, evidence accumulates that such a multiple-clock situation might be the rule rather than the exception in the animal kingdom."

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