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Moonlight plays an important role in synchronizing the reproductive cycles of marine life. Credit Carolina Castro |
How animals are able to interpret natural light sources to adjust their physiology and behavior is poorly understood. The labs of Kristin Tessmar-Raible (Max Perutz Labs Vienna, Alfred Wegener Institut, University of Oldenburg) and Eva Wolf (Johannes Gutenberg University and Institute of Molecular Biology Mainz) have now revealed that a molecule called L-cryptochrome (L-Cry) has the biochemical properties to discriminate between different moon phases, as well as between sun- and moonlight. Their findings, published in
Nature Communications, show that L-Cry can interpret moonlight to entrain the monthly (circalunar) clock of a marine worm to control sexual maturation and reproduction.
Many marine organisms, including brown algae, fish, corals, turtles and bristle worms, synchronize their behavior and reproduction with the lunar cycle. For some species, such as the bristle worm Platynereiis dumerilii, lab experiments have shown that moonlight exerts its timing function by entraining an inner monthly calendar, also called circalunar clock. Under these laboratory conditions, mimicking the duration of the full moon is sufficient to entrain these circalunar clocks. However, in natural habitats light conditions can vary considerably. Even the regular interplay of sun- and moon creates highly complex patterns. Organisms using lunar light for their timing thus need to discriminate between specific moon phases and between sun and moonlight. This ability is not well understood. "We have now revealed that one light receptive molecule, called L-Cry, is able to discriminate between different light valences," says co-first author of the study, Birgit Poehn. This Cryptochrome thereby serves as a light sensor that is able to measure light intensity and duration, thus helping the animals to choose the "right" light to adequately adjust their monthly timing system.