Kitsunezaki So, Komori Rie, Harumoto Terue
Department of Physics, Graduate School of Human Culture, Nara Women's University, Nara 630-8506, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Oct;76(4 Pt 2):046301. doi: 10.1103/PhysRevE.76.046301. Epub 2007 Oct 2.
We have investigated the bioconvection of Paramecium tetraurelia in high-density suspensions made by centrifugal concentration. When a suspension is kept at rest in a Hele-Shaw cell, a crowded front of paramecia is formed in the vicinity of the bottom and it propagates gradually toward the water-air interface. Fluid convection occurs under this front, and it is driven persistently by the upward swimming of paramecia. The roll structures of the bioconvection become turbulent with an increase in the depth of the suspension; they also change rapidly as the density of paramecia increases. Our experimental results suggest that lack of oxygen in the suspension causes the active individual motions of paramecia to induce the formation of this front.
