Sport junkie or couch potato? Always on time or often late? The animal kingdom, too, is home to a range of personalities, each with its own lifestyle. In a study just released in the journal PLOS Biology, a team led by Sören Häfker and Kristin Tessmar-Raible from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and the University of Vienna report on a surprising discovery: even simple marine polychaete worms shape their day-to-day lives on the basis of highly individual rhythms. This diversity is of interest not just for the future of species and populations in a changing environment, but also for medicine.