This roughly spherical organism called Heliozoea is slowly moving. It has many stiff, microtubule-supported projections called axopods radiating outward from the cell surface. This reminds us of the sun, after which the organism is named.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is certainly a kind of Heliozoea, but it is too small to be determined to the species level. To identify Heliozoea, we need to see the shape of the axopods and whether anything is attached to the cell surface, but it is difficult to observe these features in this tiny organism.
This heliozoan cell is about 50 microns in diameter. From the cell surface, numerous long axopods of similar length radiate outward. The organism is slowly drifting along the aggregates.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is a kind of Heliozoa which looks like the sun. Unfortunately it is too small to be classified to the species level. Organisms in the Heliozoa group can be identified by the shape of the axopods and other protrusions, and by the scales or gelatinous coat that covers the cell surface. But with this tiny organism, it is difficult to recognize these features.
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. When an enlarged image of the video is observed in high resolution, axopods (stiff, microtubule-supported projections) can be seen. Though it is moving slightly, the organism remains in the same place.
Commentary by Prof. Yuji Tsukii, Hosei University At first it was difficult to identify this organism, but the enlarged high-resolution image allows us to see a number of thin protrusions called axopods extending from the cell surface. This organism is therefore Rabdiophrys, which used to belong to the Heliozoea group. However, recently Rabdiophrys and some related organisms were reclassified as part of the Filosea group, not Heliozoea.