A ciliate with a slendar body is busily foraging among particles. Judging from the cirri in front and rear, it appears to belong to the group of Stylonychia.
Commentary by Prof. Yuji Tsukii, Hosei University The organism is not Stylonichia as mentioned in the video title; rather it belongs to genus Oxytricha or a related genus. The body of Stylonichia is hard and inflexible, so it changes directions without bending or otherwise changing its cell shape. Stylonichia is also characterized by three long cirri at the rear end.
On the other hand, Oxytricha has a soft body, and when it changes directions, the body stretches and bends toward the new direction. It is also characterized by cirri lining both sides of the cell from the tip to the rear end.
However, this video doesn’t clearly show whether or not both sides of the cell are lined with cirri from tip to rear. It looks as if there are no cirri at the midsection, which would suggest that the organism is other than Oxytricha.
However, it is certain that the organism is not Stylonychia.
After being collected from a paddy field, the sample was put on DNB agar plate (diluted nutrient broth with agar) with a drop of distilled water for 4 days, and then observed.
This large ciliate is moving around within a small area. As the center of the body is slightly narrow, this organism might be preparing to divide.
A variety of ciliates are included in this group. To identify them to the species level, it is necessary to stain the cirri by a special technique and to observe the number and arrangement of the cirri.
The cell in this video may be in the process of division, because it appears there are two sets of a peristome connected to a cytostome (mouth): one is located at the front of the cell, and the other is in the middle, just behind where the cell is slightly narrow. This narrow middle part will gradually pinch together and finally divide into two daughter cells.
After being collected from a paddy field, the sample was put on DNB agar plate (diluted nutrient broth with agar) with a drop of distilled water for 4 days, and then observed.
One of the ciliates in this video is nearly ready to divide into two daughter cells. While other ciliates swim around rapidly, this one has slowed nearly to a standstill.
This cell is obviously about to divide. The surrounding ciliates may be the same species.
When these swimming ciliates change direction, the tops of their cells also bend toward the new direction. Therefore these ciliates probably belong to genus Oxytricha.
However, according to the Monograph of the Oxytrichidae (Ciliophora, Hupotrichia) by Helmut Berger : Kluwer Academic Publishers, 1999, 113 species with similar shapes are included in genus Oxytricha. Therefore identification of this ciliate to the species level is almost impossible.
