A round Euglena
The mysterious movements inside of an aggregate are being caused by a Euglena behind it. For a while the organisms repeatedly stretches and shrinks and then settles into a round shape. The contents of its round body begin moving in a circle. The circular movement continues for a long time, even when sped up through time-lapse photography.
Commentary by Prof. Yuji Tsukii, Hosei University
This spinning organism is Euglena, though from this video it is unclear which species it is.
Sampling Date : 02 July 2009
Sampling Site : Hirose River A Google Map