Wandering from particle to particle

A brownish-black ciliate is busily swimming between particles. Despite moving within a small area, it covers a large distance for its small size. Does it feeding, or does it have some other purpose?

Commentary by Prof. Yuji Tsukii, Hosei University
This ciliate may belong to genus Prorodon.

http://protist.i.hosei.ac.jp/PDB/Im.....

As the shape of its mouth area is not clearly visible in this video, it is difficult to identify with certainty. But ciliates with a similar shape are rare, so the organism is most likely to be Prorodon.

Sampling Date : 08 August 2009

Sampling Site : Hirose River A  Google Map