A flexible flagellate
The body of this slender flagellate is 100 microns long and its single flagellum is about the same length. The organism actively moves among particles, and flexibly changes its shape to fit inside narrow spaces.
Commentary by Prof. Yuji Tsukii, Hosei University
This organism is Peranema belonging to the Euglena group, and probably Peranema trichophorum. However, information about Peranema is very limited. Although Wikipedia lists more than ten species, there are no further descriptions beyond the names. Only one species, Peranema trichophorum, is described in a standard taxonomical book on protistology. Therefore we have no knowledge of the key characteristics of other species. However, 2 or 3 species shown in the following link are obviously different from P. trichophorum.
Sampling Date : 28 May 2009
Sampling Site : Hirose River B Google Map