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A diatom caught by an unknown filamentous organism

A diatom and a long filamentous organism are stuck together in the middle of the screen. They cannot move freely, whereas other kinds of diatoms and a reddish-brown flagellate, Trachelomonas, are swimming actively.

Commentary by Prof. Yuji Tsukii, Hosei University
The swimming organisms in the first half of this video are diatoms. A string-like organism , which may be a filamentous bacterium, is moving slightly at the center of the field. It may be Cyanobacteria though it is not green. To identify it clearly, observation with high magnification is necessary.

About 26 to 28 seconds after the video starts, an organism quickly travels from the lower-left to upper-right. At a first glance it looks like Trachelomonas, but the shape of its lorica( shell-like covering) is actually very different from that of Trachelomonas.

The lorica of this organism has a dent at the front of the cell, but Trachelomonas does not have this type of lorica. Organisms having a similarly dented lorica are found in green algae, such as Dysmorphococcus and Coccomonas. The organism in this video is most likely Coccomonas, although it cannot be verified because the poor focus limits our view of the cell inside the lorica (shell), and prevents us from seeing whether or not it has two flagella.

Sampling Date : 28 May 2009

Sampling Site : Hirose River B  Google Map