Left: the green alga Volvox forms colonies that can contain thousands of cells. Each cell effectively has a single flagellum on its surface, and the flagella on different cells are able to beat in synchrony. Middle: pairs of cilia or flagella exert hydrodynamic forces on each other as they beat. Brumley et al. isolated two such flagella and varied the distance between them, L, to study the role of hydrodynamics in synchronisation. This revealed that the strength of the flow field, and hence the strength of synchronisation, is inversely proportional to L. Right: inside each flagellum, motor proteins called dyneins (dark blue) slide adjacent microtubules to drive the regular beat of the flagellum. The sensitivity of these motors to external forces may help cilia and flagella to synchronise.
FIGURE CREDIT: Frank Fox