Yet like clockwork, the crustaceans still swam out every day on 12.4 hour cycles, suggesting the creatures had a separate internal clock anchored by the tides.
"This shows that the 12.4 hour clock is independent from the circadian clock. I expect tidal rhythms in many coastal organisms will follow this rule, including insects, crabs, even plants," Kyriacou said.
In another study, researchers took a look at marine bristle worms. Bristle worms sync their spawning seasons to the waning of the moon: Most mating happens under a new moon and almost disappears during full moons.
Yet when the researchers disrupted the bristle worms circadian clocks, their monthly lunar clock still ticked on. Their lunar clocks, however, seemed to affect the timing and power of circadian-based behaviors.
"Our results suggest that the bristle worm possesses independent, endogenous monthly and daily body clocks that interact," said Kristin Tessmar-Raible, co-author of the study detailed in Cell Reports and a researcher at the University of Vienna, in a statement. "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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