Large ciliates typically reach 500 microns in length, so this giant specimen may be a world record holder at 2000 microns in length. One end appears to be fixed some long green algae as it waves the rest of body slowly back and forth. Its long body sometimes kinks and bends and we can see the cilia on the body surface vigorously moving.
Commentary by Prof. Yuji Tsukii, Hosei University This organism belongs to genus Spirostomum.
As it has only one macronucleus, it is likely to be Spirostomum teres. However, the whole body is slightly longer than that of a typical Spirostomum teres, and its shape is similar to Spirostomum intermedium. Spirostomum intermedium usually has macronuclei connected with each other almost like prayer beads. In the case of Homalozoon vermiculare, the connected macronuclei merge into a single macronucleus before division.
A similar change may occur in the nuclei of S.intermedium, though this has not been confirmed yet. Therefore this video is probably of a Spirostomum intermedium before it begins dividing.
This ciliate repeatedly extends and contracts its long, thin body, reaching a length of
more than 1000 microns when extended, and 500 microns when contracted.
The main part of the body including its mouth is narrow and dark brown, but the back end is transparent and a little pudgy.
Commentary by Prof. Yuji Tsukii, Hosei University This organism belongs to genus Spirostomum (as shown in video No.2). From its large size and cytostome (mouth) in the middle of the body, it is likely to be Spirostomum intermedium.
This ciliate, with its long, straight body, looks like a pencil that is slightly thicker in the front. There are straight lines running the length of its body. The organism continuously moves forward and backward, always along the same straight path. Sometimes it rotates along its axis.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is probably Spirostomum filum. However, it might have been torn at the rear by sand particles when it was collected.
After being collected from a paddy field, the sample was put on 1% agar plate with a drop of distilled water and kept for a few days.
Two long, narrow ciliates are moving back and forth as if they were synchronized.
Commentary by Prof. Yuji Tsukii, Hosei University This ciliate is probably Spirostomum intermedium, within the genus Spirotomum, which includes species of several sizes. The reasons for classifying it as S. intermedium include its size (500μm), and the location of the cytostome (mouth) near the center. However, other typical identifying features are missing in this video. We cannot see the macronuclei connected like a string of beads, nor can we clearly distinguish the nuclei from food vacuoles. If this ciliate has only one large macronucleus, it might be a larger variety of S.teres, which is usually 300 to 400μm long and has one large macronucleus in the middle of a slender body. So based on size, this ciliate is more likely S. intermedium.
