A Molecular Approach to Lunar Periodicity

The life of organisms is determined by rhythms. To be optimally adapted to recurring environmental processes and to synchronize within a population, organisms evolved internal oscillators ("clocks"). As there are rhythms with different period lengths, so there are internal clocks with different period lengths. Of those clocks we so far only understand the molecular mechanisms of the circadian clock, which has a period length of approximately 24hours. For all other internal oscillators (e.g. with period lengths of about a month or 14days) we do not have an understanding of their mechanisms. This work yielded the first new insights into this direction. We focused in particular on circadian and circalunar (monthly) clocks. We unravelled that the monthly clocks does not require the oscillations of the daily clock for its function. This implies that the monthly clock does not function by a superposition of two daily clocks, in fact daily and monthly clocks are independent. To further push forward into the molecular details of especially the circalunar clock, we successfully established several new techniques for our main model system, the bristle worm Platynereis dumerilii. With these techniques, we now targeted especially individual light receptors to determine which light receptor(s) is used by the circadian clock (synchronized to the environmental time by sunlight) and which light receptor(s) is used by the circalunar clock (synchronized to the environmental time by moonlight). We also determined the wavelength to which the worms light receptors respond most and how this matches with the wavelengths in the worms natural environment. During this photoreceptor analyses, we are then unexpectedly encountered that the worms also carry light receptors on their body side and belly. Interestingly, we found similar light receptors in fish, suggesting that these cells are evolutionarily old and functionally very important.As part of our evolutionary interest we also investigated the circadian and circalunar clocks of the marine midge Clunio marinus. We sequenced and assembled the genomes of different midge chronotypes and used this to unraveled molecules involved in the natural adaptation of circadian and circalunar timing.