This organism may belong to the group Rotifera. Its slender body reaches 500 microns when fully extended. Since one of the two projections at the rear end is caught on particle surface, it is desperately struggling to get free.
Commentary by Prof. Yuji Tsukii, Hosei University As Rotifera includes many species, it is difficult to say even to what genus the organism in this video belongs. At a first glance it seems to be Cephalodella but, judging from the shape of its head and rear section (caudal part), it is more likely to be Scardium. However, it cannot be classified at the species level.
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. The organism repeatedly expands and contracts its body in a narrow space surrounded by soil aggregates, seeming to look for a food.
Commentary by Prof. Yuji Tsukii, Hosei University Because the Rotifera group has many species with similar shapes, it is difficult to say even to what genus this organism belongs. The round top (front) is divided by a slant line. Two toes are at the posterior end.
In the group Rotifera, the family Proales and the family Cephalodella (including Notommata, Pleurotrocha, Eosphora, Restiula, Cephalodella, etc.) have similar characteristics.
The organism in this video is most likely Proales, which is shown in the following link.
However, the toes of this organism seem to be longer than those of Proales, and hence it could be Cephalodella. Unfortunately I do not have any examples of similar types of Cephalodella in my photo collection.
