How do aquatic microorganisms optimize feeding: is it more effective to swim through food, remain anchored while pumping food toward themselves, or join others to form a feeding colony? Despite how widespread and fundamental these strategies are, we still lack a systematic understanding of which is most efficient under different environmental conditions. This gap largely stems from the scarcity of behavioral studies combined with experimental investigations of how microorganism-generated flows stir the surrounding fluid and, in doing so, reshape nearby resource patches.
In this study, we focus on Stylonychia lemnae and found, first, that these ciliates employ chemotaxis to cluster around food patches, yet still remaining physically independent. Then, as many cells cluster on the food patch, their individual feeding flows interact, generating a chaotic collective flow throughout the cluster. Using a combination of experiments and simulations, we measured and predicted the full active chaotic flow. We found that it efficiently stirs and disperses food particles throughout the entire cluster, thereby increasing the effective patch size and helping still-foraging cells to locate food more quickly. This form of cooperative behavior highlights the surprising complexity of feeding strategies at the microscale.