The test of Arcella
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.
Based on the color and shape of the test (shell) in this video, it looks like it belonged to an Arcella, but the shell is empty now.
Commentary by Prof. Yuji Tsukii, Hosei University
For identification of Arcella to the species level, the side view of its test (shell) must be examined. The key characteristics are: (a) the ratio of the test diameter to height; (b) the ratio of the test diameter to the pseudostome (mouth) diameter; and (c) whether the test surface is smooth or depressed. Identification is difficult because this video does not show the side view of the test. But since several parts of the test appear depressed, the organism is most likely Arcella gibbosa.
Sampling Date : 16 October 2006
Sampling Site : KASHIMADAI paddy field Google Map