An unknown organism
An unknown organism stands still next to a particle. When observed in a time-lapse video, the particles inside the body move, which is usually a sign of life.
Commentary by Prof. Yuji Tsukii, Hosei University
The organism trying to catch a small diatom on a particle 
is too small to identify with certainty. 
However, there are two features that suggest it may be an amoeba: 
1) its slow movement; and 
2) its rigid semicircle outline with cytoplasm moving inside.
The organism may be a small Arcella which is trying unsuccessfully 
to catch the attached diatom.
http://protist.i.hosei.ac.jp/PDB/Im.....
Sampling Date : 18 October 2009
Sampling Site : Hirose River A Google Map
