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Moonlight influences opening and closing of oysters' shells

A new study suggests the mollusks may widen and narrow their shells depending on movement of plankton, which shifts with the lunar cycle

Plants and animals follow all sorts of biological clocks—seeds sprout when soil temperatures and day length are just right, internal circadian rhythms regulate the release of hormones in humans and other mammals, the lives of some sea creatures are ruled by the ebb and flow of tides and even moonlight is an important cue for some species to mate or hunt. Now, a new study published in the journal Biology Letters suggests oysters are one of the creatures that keep tabs on the moon, and that the lunar cycle influences how widely they open their shells.

Nicola Davis at The Guardian reports that researchers discovered the oysters’ lunar love affair after tracking 12 Pacific oysters, Crassostrea gigas, that they submerged along the French coast. They then watched them carefully through three lunar cycles, each of which lasts 29.5 days. Using electrodes, they measured how widely the oysters opened their shells every 1.6 seconds, then compared that data with data about the moon’s cycle.

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