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New research from two different teams of scientists indicates that some marine animals possess internal clocks in addition to the circadian clock, which operate independently of each other. The circadian clock tells us when to sleep and when to wake up, but many marine animals also appear to be influenced by lunar and tidal cycles.

Kristin Tessmar-Raible, a molecular neurobiologist from the University of Vienna in Austria, and her team found evidence that the marine worm ragworm operates not only by the circadian clock, but also by a circalunar clock, which is connected to the phases of the moon. This can be seen when the ragworm mates during the dark period of the new moon.

A separate team of scientists from the University of Leicester in England found that Eurydice pulchra, a crustacean related to the pill bug, operates by both a circadian clock and a circatidal clock. E. pulchra is active when the tide comes in, but burrows into the sand when the tide goes out.

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