Two light sensors decode moonlight versus sunlight to adjust a plastic circadian/circalunidian clock to moon phase

<p>Many species synchronize their physiology and behavior to specific hours. It is commonly assumed that sunlight acts as the main entrainment signal for ~24h clocks. However, the moon provides similarly regular time information. Consistently, a growing number of studies have reported correlations between diel behavior and lunidian cycles. Yet, mechanistic insight into the possible influences of the moon on ~24hr timers remains scarce.</p> <div> <div> <div class="msocomtxt"> <p class="MsoNormal"><span>We have explored the marine bristleworm </span><em><span>Platynereis dumerilii</span></em><span> to investigate the role of moonlight in the timing of daily behavior. We uncover that moonlight, besides its role in monthly timing, also schedules the exact hour of nocturnal swarming onset to the nights' darkest times. Our work reveals that extended moonlight impacts on a plastic clock that exhibits &lt;24h (moonlit) or &gt;24h (no moon) periodicity. Abundance, light sensitivity, and genetic requirement indicate that the <em>Platynereis </em>light receptor molecule r-Opsin1 serves as a receptor that senses moonrise, whereas the cryptochrome protein L-Cry<em> </em>is required to discriminate the proper valence of nocturnal light as either moon- or sunlight. Comparative experiments in <em>Drosophila </em>suggest that cryptochrome's principal requirement for light valence interpretation is conserved. Its exact biochemical properties differ, however, between species with dissimilar timing ecology.</span></p> <p class="MsoNormal"><span>Our work advances the molecular understanding of lunar impact on fundamental rhythmic processes, including those of marine mass spawners endangered by anthropogenic change.</span></p> </div> </div> </div>