The copepod species Calanus finmarchicus schedules its day using a genetic clock that works independently of external stimuli. The clock shapes the copepod’s metabolic rhythms and daily vertical migration. This, in turn, has an enormous influence on the entire food web in the North Atlantic, where Calanus finmarchicus is a central plankton species. Wherever the high-calorie copepod is found determines where its predator species are. The results of the study will be published in the journal Current Biology.