Fluid circulation driven by collectively organized metachronal waves in swimming T. aceti nematodes

Recent experiments have shown that the nematode T. aceti can assemble into collectively undulating groups at the edge of fluid drops. This coordinated state consists of metachronal waves that drive fluid circulation inside the drop. We experimentally measure the properties of these flows and compare them to an analytical model. For the latter, we develop a quasi two-dimensional hydrodynamics model using the Stokes flow approximation. The periodic motion of the nematodes constitutes our moving boundary condition that drives the flow. Our model suggests that large amplitude excursions of the nematodes tails produce fluid circulation. We discuss the constraints on containers that would enhance fluid motion, which could be used in the future design of on-demand flow generating systems.