The marine midge Clunio marinus inhabits the intertidal zone of the European Atlantic Coast from Spain to Norway. In adaptation to its habitat, the marine insect has timed its development and reproduction precisely to the rhythm of the tides: Adults emerge and reproduce only during the low tide of spring tide days, when the water is as low as possible. This remarkable synchronisation is achived by combining a circalunar clock with a circadian clock.
While the pattern of the tides is highly regular at a given geographic location, it differs tremendously between geograpic locations along the coastline. Clunio populations from different places along the coast display a vast variety of corresponding genetic adaptations in their circalunar and circadian clocks. These adaptations involve the exact timing of behaviour, but also the abiity of environmental cues to reset the clocks or the entire loss of certain clocks in certain habitats.
Population genetic studies suggest that most of these timing adaptations have evolved in less that 20,000 years, after the last ice age. The Clunio marinus reference genome greatly enhances the possibilities to study the manifold timing adaptations of Clunio, giving insight into how evolution shapes biological timekeeping mechanisms to match the requirements of specific habitats.
In Clunio, evolutionary and functional studies go hand in hand: Identifying the genes underlying local adaptations in timing may highlight novel molecular components of the circadian clock and the still enigmatic circalunar clock. In turn, unravelling the molecular mechanisms of Clunio's circadian and circalunar clocks facilitates the study of the evolutionary processes by which these clocks adapt to their environment.
Reasearch on the timing adaptations of Clunio marinus is carried out by the Max Planck Research Group "Biological Clocks" at the Max Planck Institute for Evolutionary Biology. Further information can be obtained from their webpage or from Tobias Kaiser.