This dark-brown ciliate is extraordinarily long at more than 1500 microns. It quickly passes through numerous narrow spaces between particles. Its cilia can be observed when it stops. There is a transparent part at the end of the body.
Commentary by Prof. Yuji Tsukii, Hosei University Judging from its long cell size and cytostome at the center, this organism is likely to be Spirostomum intermedium. However, for identification, it is necessary to confirm that its macronuclei are shaped like beads.
This ciliate is similar to ciliate (1) in its extreme length as well as behavior. There are some interesting differences, however. Ciliate (2) has stripes running the length of its flat, ribbon-like body; and when it twists, we can see that the rear end is not rounded. The surface of both ciliate (1) and (2) is covered with cilia.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is Spirostomum intermedium. As the video was taken using high magnification, we can clearly see the vertical lines on its cell surface.