Non-local hydrodynamic interactions between undulating flagella

The emergence of synchronized or coordinated behaviours is a well-documented phenomenon pertaining to interacting pairs, bundles, or groups of slender beating filaments such as arrays of airway epithelial cilia, or the flagella of the spherical alga Volvox carteri. More recent experimental and theoretical work highlight the key role of flagellar waveform compliance in mediating measured synchronization regimes. Conceptual, low-dimensional models which consider elastohydrodynamic interactions between nearby flagella often assume large interflagellar separations, which are not always realistic and cannot readily capture all of the observed dynamics. Here we visualize and quantify symmetry-breaking processes in novel synchronization modes of algal flagella during the physiological "shock response", demonstrating the extent to which nonlocal respresentations of hydrodynamic interactions between extended microfilaments are necessary in the context of asymptotically-close interflagellar distances.