Cell body rocking is a dominant mechanism for flagellar synchronization in a swimming alga

TL;DR

This study demonstrates that cell body rocking, caused by flagellar perturbations, is the primary mechanism for flagellar synchronization in swimming algae, supported by hydrodynamic modeling and experimental validation.

Contribution

The paper introduces a new understanding that cell body rocking dominates flagellar synchronization, challenging previous assumptions of hydrodynamic coupling between flagella.

Findings

Cell body rocking restores flagellar synchronization.

Hydrodynamic interactions between flagella are negligible.

Experimental data confirms the role of cell body rocking.

Abstract

The unicellular green algae Chlamydomonas swims with two flagella, which can synchronize their beat. Synchronized beating is required to swim both fast and straight. A long-standing hypothesis proposes that synchronization of flagella results from hydrodynamic coupling, but the details are not understood. Here, we present realistic hydrodynamic computations and high-speed tracking experiments of swimming cells that show how a perturbation from the synchronized state causes rotational motion of the cell body. This rotation feeds back on the flagellar dynamics via hydrodynamic friction forces and rapidly restores the synchronized state in our theory. We calculate that this `cell body rocking' provides the dominant contribution to synchronization in swimming cells, whereas direct hydrodynamic interactions between the flagella contribute negligibly. We experimentally confirmed the coupling between flagellar beating and cell body rocking predicted by our theory. This work appeared also in the Proceedings of the National Academy of Science of the U.S.A as: Geyer et al., PNAS 110(45), p. 18058(6), 2013.