A round, dark brown flagellate with a long flagellum swims around for a while, then stops beside a particle, still waving its flagellum vigorously. A hard lorica surrounds the body, so this organism may belong to the group Trachelomonas.
Commentary by Prof. Yuji Tsukii, Hosei University This organism Trachelomonas belongs to the Euglenid group
and is surrounded by a shell.
The features of the cell surface determine the organism’s species.
An organism with a smooth surface is probably Trachelomonas oblonga,
while one with a rough surface may be Trachelomonas granulose
or Trachelomonas intermedia.
The organism in this picture appears to be Trachelomonas oblonga.
The sample was observed immediately after being collected from a paddy field.
An organism suddenly appears and gets stuck to a large aggregate. It struggles to break free, but the aggregate seems to be too sticky to allow the organism to escape.
Commentary by Prof. Yuji Tsukii, Hosei University As the oval shape does not change even during the struggle, a shell probably surrounds this organism. The green color inside the cell is from chloroplasts and the reddish part is the eye-spot (stigma). This organism may belong to genus Trachelomonas.
The shell (lorica) is about 25μm long and its nearly round shape is only slightly oval. The surface of the shell is smooth and without a protrusion (collar). From these features, the organism may be Trachelomonas dybowskii.
The sample was observed immediately after being collected from a paddy field.
The whole surface of this green organism is covered with spines. We were able to record it for only a short time.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is a type of Euglena with a lorica (shell), probably Trachelomonas crispa or a related species. In Trachelomonas crispa, short spines cover the whole surface of the lorica; there is a rather long spine at the top instead of a collar; and the body gradually tapers at the rear. However, the organism in this video is characterized by a sharply tapered rear end, which is different from the typical Trachelomonas crispa.
Such a difference might be caused by intraspecific variation. But I cannot be sure because I have not observed many examples of Trachelomonas crispa.
If there are other Trachelomonas crispa in this same sample that display a similar sharp narrowing at the rear, intraspecific variation (variation within species) might be the best explanation. On the other hand, if there aren’t any other Trachelomonas crispa with the same rear end, the organism in the video may belong to another species.
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.
A large diatom cell slowly goes into and later backs out of a large aggregate. Long filamentous and rod-shaped bacteria are moving around. Some of the rod-shaped bacteria seem to gather around the rear of the diatom cell.
Commentary by Prof. Yuji Tsukii, Hosei University This diatom belongs to genus Pinnularia.
The organism is seen from the side view (girdle face), which does not show the pattern. We can’t be sure from this video whether or not the organism is in the process of division.
Flagellates vigorously swimming around are probably Trachelomonas volvocina.
After being collected from a paddy field, the sample was put on 1% agar plate with a drop of distilled water and kept in the dark for 4 days.
In the first scene of this video, a testate amoeba Arcella is moving slowly among aggregates. In the second scene, the amoeba notices a green organism that comes near. In the last scene, the Arcella has caught the green organism and is consuming it. Unfortunately, the video did not film the moment of capturing the organism.
Commentary by Prof. Yuji Tsukii, Hosei University This large amoeba with a disk-shaped shell (test) and thick pseudopodia is a testate amoeba called Arcella.
The green organism that approaches belongs to genus Trachelomonas,
because it is surrounded by a shell (lorica) and exhibits characteristic
locomotion. Trachelomonas is also characterized by a red eyespot in its
cytoplasm.
Newly formed shells of trachelomonas are transparent and gradually
become reddish-brown. As this organism has a transparent shell, it has
probably just divided.
The organism might be Trachelomonas crispa, but we cannot see the long, spiky spines surrounding the opening where the flagellum extends, which are a characteristic feature of Trachelomonas crispa.
Another possibility is that the organism belongs to genus Strombomonas.
However, the opening (outlet) for the flagellum of Strombomonas is
characterized by a narrower structure like a bottleneck. Therefore the
organism may be Trachelomonas rather than Strombomonas.
After being collected from a paddy field, the sample was put on 1% agar plate with a drop of distilled water and kept in the dark for 4 days.
A green elliptic organism is moving around within a small area. Its surface is a shell (lorica) covered with spines.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is Trachelomonas crispa or a related species. One of the features of Trachelomonas crispa is that long spines surround the opening at the top where the flagellum comes out. The spines observed in this video are not the typical shape, so perhaps they have been damaged by the surrounding sand particles.
