Coordinated Beating of Algal Flagella is Mediated by Basal Coupling

TL;DR

This paper investigates how basal body coupling and hydrodynamic interactions coordinate flagella in unicellular algae, revealing that internal cellular mechanisms significantly influence synchronization beyond fluid dynamics alone.

Contribution

It demonstrates that basal body coupling within cells plays a crucial role in flagellar synchronization, supplementing hydrodynamic interactions, and explores how cellular architecture affects flagellar coordination.

Findings

Basal body coupling affects flagellar synchronization.

Hydrodynamic interactions alone are insufficient for full coordination.

Cellular architecture influences flagellar gait patterns.

Abstract

Cilia and flagella often exhibit synchronized behavior; this includes phase locking, as seen in {\it Chlamydomonas}, and metachronal wave formation in the respiratory cilia of higher organisms. Since the observations by Gray and Rothschild of phase synchrony of nearby swimming spermatozoa, it has been a working hypothesis that synchrony arises from hydrodynamic interactions between beating filaments. Recent work on the dynamics of physically separated pairs of flagella isolated from the multicellular alga {\it Volvox} has shown that hydrodynamic coupling alone is sufficient to produce synchrony. However, the situation is more complex in unicellular organisms bearing few flagella. We show that flagella of {\it Chlamydomonas} mutants deficient in filamentary connections between basal bodies display markedly different synchronization from the wild type. We perform micromanipulation on configurations of flagella and conclude that a mechanism, internal to the cell, must provide an additional flagellar coupling. In naturally occurring species with 4, 8, or even 16 flagella, we find diverse symmetries of basal body positioning and of the flagellar apparatus that are coincident with specific gaits of flagellar actuation, suggesting that it is a competition between intracellular coupling and hydrodynamic interactions that ultimately determines the precise form of flagellar coordination in unicellular algae.