Description

Swimming and feeding behaviors of Paramecium multimicronucleatum with fore-aft asymmetric body shapes are studied both experimentally and numerically. Ciliates, like Paramecia, with fore-aft asymmetric shapes preferentially swim along the slender anterior while feeding fluid into the oral groove located at the center of the body. Because both feeding and swimming are governed by fluid flow, it is important to reveal the role of fluid mechanics around a fore-aft asymmetric body. However, to date, Paramecia’s preferred swimming direction has not been investigated in detail and its potential benefits are not understood. In this study, we employ microparticle image velocimetry (µ-PIV) to measure the flow patterns around a swimming Paramecium and we use the boundary element method to investigate the effect of the body shape on the velocity fields, and on the swimming and feeding efficiencies. The simulation and experimental results are in agreement showing that the velocity fields exhibit a fore-aft asymmetry and the magnitude of the velocity decreases as r – 2 from the body surface. These observations are quite different from symmetric flows present in traditional squirmer models where steeper velocity decay (r – 3) is expected. According to our simulation results, this unexpected finding is attributed to the fore-aft body asymmetry. Moreover, the shape asymmetry revealed an optimum combined efficiency of swimming and feeding, which could possibly explain the Paramecium’s preferred swimming direction.

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Paramecia swimming in viscous flow

Swimming and feeding behaviors of Paramecium multimicronucleatum with fore-aft asymmetric body shapes are studied both experimentally and numerically. Ciliates, like Paramecia, with fore-aft asymmetric shapes preferentially swim along the slender anterior while feeding fluid into the oral groove located at the center of the body. Because both feeding and swimming are governed by fluid flow, it is important to reveal the role of fluid mechanics around a fore-aft asymmetric body. However, to date, Paramecia’s preferred swimming direction has not been investigated in detail and its potential benefits are not understood. In this study, we employ microparticle image velocimetry (µ-PIV) to measure the flow patterns around a swimming Paramecium and we use the boundary element method to investigate the effect of the body shape on the velocity fields, and on the swimming and feeding efficiencies. The simulation and experimental results are in agreement showing that the velocity fields exhibit a fore-aft asymmetry and the magnitude of the velocity decreases as r – 2 from the body surface. These observations are quite different from symmetric flows present in traditional squirmer models where steeper velocity decay (r – 3) is expected. According to our simulation results, this unexpected finding is attributed to the fore-aft body asymmetry. Moreover, the shape asymmetry revealed an optimum combined efficiency of swimming and feeding, which could possibly explain the Paramecium’s preferred swimming direction.