Reorganization of complex ciliary flows around regeneratingStentor coeruleus

Abstract

The phenomenon of ciliary coordination has garnered increasing attention in recent decades and multiple theories have been proposed to explain its occurrence in different biological systems. While hydrodynamic interactions are thought to dictate the large-scale coordinated activity of epithelial cilia for fluid transport, it is rather basal coupling that accounts for synchronous swimming gaits in model microeukaryotes such as Chlamydomonas. Unicellular ciliates present a fascinating yet understudied context in which coordination is found to persist in ciliary arrays positioned across millimetre scales on the same cell. Here, we focus on the ciliate Stentor coeruleus , chosen for its large size, complex ciliary organization, and capacity for cellular regeneration. These large protists exhibit ciliary differentiation between cortical rows of short body cilia used for swimming, and an anterior ring of longer, fused cilia called the membranellar band (MB). The oral cilia in the MB beat metachronously to produce strong feeding currents. Remarkably, upon injury, the MB can be shed and regenerated de novo. Here, we follow and track this developmental sequence in its entirety to elucidate the emergence of coordinated ciliary beating: from band formation, elongation, curling and final migration towards the cell anterior. We reveal a complex interplay between hydrodynamics and ciliary restructuring in Stentor , and highlight for the first time the importance of a ring-like topology for achieving long-range metachronism in ciliated structures. This article is part of the Theo Murphy meeting issue ‘Unity and diversity of cilia in locomotion and transport’.

Origins of eukaryotic excitability

“…This means that while diffusion alone is sufficient to ensure prokaryotes are well-stirred, eukaryotes must have acquired alternative means of advecting flows. Cilia and flagella are often used to create large-scale flows (up to mm s −1 ) for filter feeding, or for replenishing the local nutrient concentration around cells [ 324 , 325 ]. For a cell with length L , moving at speed U , the importance of advection over diffusion is captured by the Péclet number Pe = UL / D , the ratio between advective ( L / U ) and diffusive timescales ( L 2 / D ).…”

On the unity and diversity of cilia

“…We begin with ciliary beating in Stentor-a unicellular protist that feeds using an anterior oral apparatus. Wan et al [57] take advantage of Stentor's unique regenerative capabilities to study the de novo assembly of a new oral apparatus, and the emergence of long-range metachronal coordination of the oral cilia across micrometric distances. In many animals, ciliated surfaces can also become internalized.…”

Microfluidic guillotine reveals multiple timescales and mechanical modes of wound response in Stentor coeruleus

“…Briefly, a 1D coordinate system along the membranellar band was defined using ImageJ and used to construct a region of interest. 2D kymographs of image intensity were computed and autocorrelated to determine the spatiotemporal coordination of the beating cilia following the method published by Wan et al[42]…”

“…High-speed images of the cells were taken at 5000 fps with a 20x objective using the Phantom v341 camera and analyzed as described previously [42]. Briefly, a 1D coordinate system along the membranellar band was defined using ImageJ and used to construct a region of interest.…”

“…Briefly, a 1D coordinate system along the membranellar band was defined using ImageJ and used to construct a region of interest. 2D kymographs of image intensity were computed and autocorrelated to determine the spatiotemporal coordination of the beating cilia following the method published by Wan et al [42] 5.10 Experimental design and statistical analysis Cells used for experiments were always used the second day after feeding to ensure consistency (Additional File 1: Notes S1, S3). At least 3 biological replicates were performed for each experimental group in the wound repair assay experiments.…”