Abstract
A flow around a brine shrimp as an animal plankton was investigated by using the PIV measurement. The brine shrimp moves by beating its arms. This is one of typical ways to obtain thrust and control for a direction of motion in the low Reynolds number circumstances. We found that a vortex pair moving with arms appeared during downstroke motion. The center of the vortex located on a middle of the arm when the brine shrimp moved forward. The other vortex pair formed at the end of upstroke motion. The scale of the latter vortex was smaller than the former vortex.
