  Coordinated cilia are used throughout the natural world for micronscale fluid
transport. They are often modelled with regular filament arrays on fixed,
planar surfaces. Here, we simulate hundreds of interacting active filaments on
spherical surfaces, where defects in the cilia displacement field must be
present. We see synchronised beating towards or about two defects for spheres
held fixed. Defects alter filament beating which causes the sphere to move once
released. This motion feeds back to the filaments resulting in a whirling state
with metachronal behaviour along the equator.
