A dark green Euglena is moving very slowly. The body is longer and seemingly less flexible compared to other types of Euglena. It twists its body but does not expand and contract. This type has a striped pattern on its surface.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is Euglena spirogyra, which is often found in wet media such as marsh, swamp and paddy.
As shown at the above link, there are various sizes of Euglena spirogyra. Usually it stays still in the lowest water layer, but the organism in this video is actively moving around.
The mysterious movements inside of an aggregate are being caused by a Euglena behind it. For a while the organisms repeatedly stretches and shrinks and then settles into a round shape. The contents of its round body begin moving in a circle. The circular movement continues for a long time, even when sped up through time-lapse photography.
Commentary by Prof. Yuji Tsukii, Hosei University This spinning organism is Euglena, though from this video it is unclear which species it is.
River bottoms are composed of accumulated aggregated particles, pieces of sand grains and pland debris, whose surfaces are covered with bacteria. They offer small flagellates and ciliates a rich source of nutritious food. Single cells of diatoms as well as their chains can also be observed in this flourishing microbial world.
Commentary by Prof. Yuji Tsukii, Hosei University The organism is not Diatoma but Biddulphia or Pleurosira.
Lines can be observed at both ends of this chain of cells. These lines appear after chloroplasts disappear in the dead cells, as shown in the following web page.
Several Euglena organisms go in and out of a large aggregate as if it were a comfortable residence for them.
Commentary by Prof. Yuji Tsukii, Hosei University The organism may be Euglena viridis, but because the shape of the chloroplasts is vague in this video, the species level cannot be determined.
Various organisms such as Coleps, Strobilidium , Euglena, Diatom, and some small flagellates can be seen. This is the world of active microorganisms, which cannot be recognized with naked eye.
Commentary by Prof. Yuji Tsukii, Hosei University (a) It is difficult to determine whether this organism is Strobilidium or Strombidium.
Strobilidium
After an intense struggle, an euglena frees itself from a particle and swims around for a while. However it gets caught by another particle. It changes its flexible shape repeatedly in its effort to break free.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is probably Euglena viridis.
Compared to the most common E. viridis, its body appears larger than usual, but such changes in size may occur depending on living conditions. The cell appears transparent and without particles in the rear half of the body. However, there are chloroplasts arranged like a ribbon along the cell wall to the rear end.
Commentary by Prof. Yuji Tsukii, Hosei University There are several species of Euglena with a similar appearance. They can be distinguished from each other by the shape and arrangement of chloroplasts in the cytoplasm. Judging from the pictures of the above three species taken by myself, the Euglena in this video is probably Euglena schimitzii.
An inactive flagellate is sitting completely still without moving. One after another, two small ciliates come to the front of the inactive flagellate, and stop as to check on it before they leave. Soon these ciliate return for another visit, and it looks like the two different kinds of organisms are communicating. To our surprise, the flagellate suddenly becomes active, contracting its body and shooting out of our view.
Commentary by Prof. Yuji Tsukii, Hosei University The title and the commentary of this video should be changed, because the organisms shown are flagellates, not ciliates. In this video, we can see two types of flagellates belonging to Euglenales and Cryptomonadales.
The Euglenales organism does not have any cilia and a few relatively large pyrenoids can be seen inside of the cell. Therefore, the organism is probably Euglena agilis, but we cannot rule out the possibility that the organism could be E. viridis. Because cell outlines are similar in both E. agilis and E. viridis
The shape of the chloroplasts is also an important point in distinguishing the above two Euglena species. However it is difficult to see the precise shape of the chloroplasts in this video.
In this video, the Cryptomonadales organism has light-brown chloroplasts along the sides of the cell with a pyrenoid at the center. These characteristics are typical of Cryptomonas or Chroomonas.
Here we can see nine Euglena cells that are completely still. Are they weakened, or have their sticky bodies become caught on the wall of the container? A small ciliate, Aspidisca, and a large slender ciliate pass nearby.
Commentary by Prof. Yuji Tsukii, Hosei University Various types of flagellates are included in the Euglena group.
Some species constantly swim actively, while others simply lie still
on the bottom surface.
A third type of flagellate exhibits both behaviors, alternately swimming
or staying still.
After stops moving, the organism often exhibits a simple round shape,
and the shape of its chloroplasts are difficult to distinguish.
This organisms looks like Euglena viridis, which can be seen at the following address.
Two single-celled flagellates, called Euglena, have become stuck on a solid surface and cannot move. When another Euglena joins them, it attaches itself to the first pair and stops moving as well. Meanwhile, various kinds of flagellates and ciliates are passing nearby.
Commentary by Prof. Yuji Tsukii, Hosei University The organism in the first scene is certainly Euglena viridis.
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.
This Euglena cannot move freely, probably because its flagellum or some part of its body is stuck on the container surface. It expands and contracts its body in a desperate struggle to get free.
Commentary by Prof. Yuji Tsukii, Hosei University Without checking the shape and distribution of chloroplasts inside the cell,
it is difficult to identify the exact species within the Euglenid group.
In this video, the organism seems to be attached to the glass surface.
The repeated expansion and contraction of the cell is called
“Euglena movement”.
A Euglena and an unknown small organism are standing still in this view. Only the flagellum of the Euglena moves somewhat feebly.
Commentary by Prof. Yuji Tsukii, Hosei University Though the title of this video is a weakened Euglena,
some species in the Euglena group exhibit a round shape
and remain motionless even when in an active state.
Therefore we cannot say the organism is “weakened”
by observing its behavior.
The Euglena agilis cultivated in my lab divide without swimming
and keep their round shape.
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.
Being covered with small particles, this flagellate looks like a sand aggregate with a long narrow flagellum extending forward. Is the flagellate using the particles as an armor to protect itself against enemy attacks?
Commentary by Prof. Yuji Tsukii, Hosei University This flagellate may be Peranemopsis granulifera in the Euglena group.
The characteristics of Peranemopsis granulifera are a cell surface covered with fine sandy particles and a long flagellum extending forward. Both features can be seen in this video, although the flagellum is not so clear.
However, this organism is nearly 100μm long, which is longer than the usual 40-70μm cell length of E. viridis, so it could belong to another larger species.
To determine whether or not this organism is E. viridis, the shape of the chloroplast must be examined, but unfortunately it cannot be seen clearly in this video.
After being collected from a paddy field, the sample was put on 1% agar plate with a drop of distilled water and kept for four days.
At a first glance this looks like a round green organism with a red part in the center.
But after a while, the organism elongates and swims around, revealing itself as a Euglena. Later it gradually returns to the former shape and stops moving entirely.
Commentary by Prof. Yuji Tsukii, Hosei University This video records a Euglena in the process of changing shape. Many species are included in Euglena and recently the standards for classification have changed a lot. Therefore identification of Euglena has become more difficult.
It is necessary to know the shape of the chloroplast, surface appearance, changeability of its body shape, and the shape and number of its paramylon particles.
The round cell in this video is nearly 200μm in diameter. Ribbon-like protoplasts inside seem to spread radially from the center. These features suggest that the organism is Euglena schmitzii, but if you refer to my photograph of E. schmitzii, you will not see a red part and the shape is different. Therefore the organism cannot be determined to the species level.
The sample was observed immediately after being collected from a paddy field.
In this green spherical organism, the cytoplasm with a red spot is slowly rotating. Is this organism Euglena?
Commentary by Prof. Yuji Tsukii, Hosei University It cannot be determined exactly what this organism is. However, the cytoplasm is continually moving inside of a transparent round shell, and we can see green particles that seem to be protoplasts and a reddish spot in the cytoplasm. Therefore it might be Euglena in a dormant state.
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 Euglena cell is swimming among bacterial cells. Its body appears less flexible than other kinds of Euglena cells.
Commentary by Prof. Yuji Tsukii, Hosei University This organism belongs to genus Euglena.
As the cell length is shorter than 100μm, this is a medium-sized Euglena.
Genus Euglena is identified by the following characteristics: body shape, surface appearance, shape of the chloroplasts, and shape of the paramylon body.
We can clearly see the long, narrow cell shape with a sharply tapered rear end in this video, but other features are not clear enough to determine the species of this Euglena. Euglena caudata and Euglena anabaena have a similar cell shape but their bodies are softer and more malleable.
The Euglena cell in this video is neither soft nor flexible. I have often taken photos of similar types of Euglena, but still have not been able to identify them.
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.
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 flagellate with a long flagellum is slowly moving around among aggregates. If it weren’t moving, we might be fooled into thinking it is just another aggregate, because its whole surface is covered with small particles. Is this appearance designed to disguise itself from enemies?
Commentary by Prof. Yuji Tsukii, Hosei University This organism is Peranemopsis granulifera in the Euglena group. It is characterized by one flagellum and a unique cell surface that is almost wholly covered with sandy particles. The cell of this organism is flexible (similar to Peranema), and when the cell changes shape as it moves around, the sandy particle cover also stretches to adapt to the cell’s flexing.
