In this fluid dynamics video we investigate the flow field around straight-line swimming and right and left turning Paramecia using micro- particle image velocimetry ({mu}PIV). A Paramecium controls its ciliary beating to produce different fluid velo
cities on either side of its body. This phenomenon is visualized by applying {mu}PIV to images in which Paramecia swim in a dilute suspension of 1 {mu}m polystyrene spheres. Paramecia that swim straight exhibit similar magnitudes of velocity on either side of their bodies. In contrast, right-turning Paramecia exhibit greater magnitudes of velocity on their right sides, while left-turning organisms show the opposite.
