In the vast, nutrient-poor regions of the world’s oceans, there is a constant struggle for survival. Yet tiny organisms known as Collodaria have thrived there for millions of years. These Collodaria host microscopically small algae that are essential for survival. A research team of the Cluster of Excellence »Balance of the Microverse« at the University of Jena has now uncovered the metabolic secret behind the symbiosis and provides entirely new insights into marine ecosystems.