Paramecium swimming in capillary tube

TL;DR

This study investigates how Paramecium multimicronucleatum's swimming behavior is affected by confinement in capillary tubes, combining experimental observations with theoretical modeling to understand boundary interactions.

Contribution

It provides a combined experimental and theoretical analysis of Paramecium swimming in confined geometries, highlighting the importance of boundary effects on locomotion.

Findings

Paramecium transitions from helical to straight trajectories in narrower tubes

Theoretical model as an undulating cylinder with pressure gradient matches experiments

Boundary effects significantly influence swimming velocities and trajectories

Abstract

Swimming organisms in their natural habitat navigate through a wide array of geometries and chemical environments. Interaction with the boundaries is ubiquitous and can significantly modify the swimming characteristics of the organism as observed under ideal conditions. We study the dynamics of ciliary locomotion in Paramecium multimicronucleatum and observe the effect of the solid boundaries on the velocities in the near field of the organism. Experimental observations show that Paramecium executes helical trajectories that slowly transition to straight line motion as the diameter of the capillary tubes decrease. Theoretically this system is modeled as an undulating cylinder with pressure gradient and compared with experiments; showing that such considerations are necessary for modeling finite sized organisms in the restrictive geometries.