Moonlight Makes It Right

Medscape Staff

June 01, 2022

All organisms have two photoreceptors that make the moon's role in setting body clocks just as important as that of the sun, according to Austrian researchers with the University of Vienna, the Medical University of Vienna, and the Alfred Wegener Institute.

What to know:

  • All animals possess circadian clocks, and many species synchronize their physiology and behavior to specific hours based on changes of sunlight and darkness, with the moon playing just as important a role as the sun.

  • Marine bristle worms schedule their reproduction for just a few days of the month and were found to synchronize release of their eggs and sperm freely into the open seawater according to moon cycles, taking advantage of the darkest portion of the night.

  • The time of moonlight changes every day by about 50 minutes and the plasticity of the clock allows the worms to factor in these changes.

  • Scientists found that the combinatorial functions of two light-sensitive circadian photoreceptors called opsin and a cryptochrome help moonlight and sunlight work together to adjust the daily clocks of organisms.

  • The specific decoding of moonlight and its impact on circadian clocks is relevant for many species and could help understand the origin and consequences of biological timer plasticity and why different species' daily clocks can run with different speeds with natural timing cues.

This is a summary of the article "Two light sensors decode moonlight versus sunlight to adjust a plastic circadian/circalunidian clock to moon phase" published by Proceedings of the National Academy of Sciences on May 30, 2022. The full article can be found

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