An amoeba moves slowly by extending fine pseudopods in all directions. The center of its body is full of food particles and seems to be slightly rigid.
Commentary by Prof. Yuji Tsukii, Hosei University This amoeba is either Filamoeba or Vampyrella. When it moves, numerous threadlike pseudopodia are extended from the cell surface.
The body shape is typical of Filamoeba, whereas the red particles inside the cell are more indicative of Vampyrella. The reddish color comes from Spyrogira and other foods, and the color fades as the organism is starved.
Vampyrella usually takes a spherical form like Heliozoa, but when moving actively, it cannot be distinguished from Filamoeba.
Usually Vannella moves exhibiting a specific shape as shown in the above link. However the organism in this video doesn’t move around, which makes it difficult to decide what it is. It is also possible that the organism is not Vannella, but rather may be a dead protozoan cell whose body is collapsing, causing it to exhibit a similar shape to Vannella.
An amoeba extends a number of fine pseudopods and moves very slowly. Here its movements is sped up to 10 times the normal speed, so it appears to be moving quickly. A large particle attached to the back of the amoeba is being dragged along by the organism. When it arrives at the surface of an aggregate, the amoeba squeezes its flexible body through a narrow opening, leaving the particle behind.
Commentary by Prof. Yuji Tsukii, Hosei University This amoeba is Vexillifera or closely-related organism.
Its method of locomotion is similar to that of Mayorella, but unlike Mayorella,
this organism extends many narrow pseudopodia (Dactylopodia) forward.
This testate amoeba has contracted its pseudopods inside its shell and remains still.
Commentary by Prof. Yuji Tsukii, Hosei University The shell surface of the Arcella (testate amoeba) is generally smooth, but in this video, various particles seem to be attached to the surface. Also, the position of the pseudostome (opening) in this organism is not at the exact center of the body. If it were, the organism might be a different kind of testate amoeba other than Arcella.
A hidden amoeba extends several pseudopodia from behind the end of one particle. The amoeba partially appears, but quickly hides by covering itself with fragments of particles. Next the amoeba appears from the end of a different particle and disappears carrying two small fragments with it. The amoeba repeatedly appears and disappears, but never completely shows itself. The behavior of the amoeba toward the surrounding particles is quite mysterious.
Commentary by Prof. Yuji Tsukii, Hosei University It is difficult to say what this amoebae is, because the whole body is not shown in this video. The key is its characteristic pseudopodia. Large amoeba (Amoeba proteus, Trichamoeba and Polychaos etc.) do not extend pseudopodia like these. Most medium-sized amoeba (Mayollera, Saccamoeba etc.) do not extend such long pseudopodia.
The pseudopodia of Vexillifera are similar to this organism, but we cannot say whether the organism is really Vexillifera without checking its locomotive form.
Dinamoeba is also known to extend a similar type of pseudopodia though I have not confirmed it.
Therefore this organism cannot be identified without checking its whole body.
A large amoeba is gliding along smoothly. Numerous food particles can be seen in its transparent body. Rather than extend pseudopodia to capture food, the amoeba extends part of its body in the direction of movements, which allows it to capture food. Sometimes it throws out food particles but then engulfs them again.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is Vannella miroides in genus Vannella.
The locomotive form of Vannella is like an open folding fan, and the locomotive form of Vannella miroides is characterized by pseudopodia with wavy edges.
Here a large amoeba is actively hunting and catching food in various ways. When a food particle becomes caught on the tip of the pseudopodium, the pseudopodium carries the food to the center of its body, by becoming shorter and broader until the food is engulfed.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is possibly a floating Vannella.
It usually attaches onto solid surfaces and appears like a flat fan,
but when it is torn off from the surface by water movement,
it transforms into a radial shape.
Floating in water, Vanella expands its narrow pseudopodia
to find a new surface to which it can attach.
Vanella looks for food - bacteria and small protozoa - as it moves
along solid surfaces.
When a ciliate or flagellate accidently runs into the amoebas body, two pseudopodia tightly grasp the unlucky prey and transfer it to the central part. At first the prey struggles to get free, but soon stops moving. Finally the prey loses its shape and becomes unrecognizable.
Commentary by Prof. Yuji Tsukii, Hosei University This organism resembles Vanella in its radial shape,
but unlike Vanella, it catches food while floating freely.
The organism may be Vexillifera or it may belong to a related family.
It sometimes moves on a solid surface, while at other times it proceeds
while swaying its long pseudopodium in front.
An important criterion for classifying amoeba is their method of locomotion.
Since amoeba appear similar when they are floating,
it is difficult to determine what species this organism is.
When the amoeba concentrates on catching food using one or two pseudopodia, the remaining pseudopodia become very short. When many food particles approach all at once, the amoeba becomes confused and cannot decide which pseudopodium to extend. When this happens, the hunt is a complete failure.
Commentary by Prof. Yuji Tsukii, Hosei University The organism is Vexillifera.
Here a large amoeba is actively hunting and catching food in various ways. When a food particle becomes caught on the tip of the pseudopodium, the pseudopodium carries the food to the center of its body, by becoming shorter and broader until the food is engulfed.
Commentary by Prof. Yuji Tsukii, Hosei University The beginning of this video, the amoeba looks like it might be a floating Vannella, which is difficult to distinguish from Vexillifera.
When a ciliate or flagellate accidently runs into the amoebas body, two pseudopodia tightly grasp the unlucky prey and transfer it to the central part. At first the prey struggles to get free, but soon stops moving. Finally the prey loses its shape and becomes unrecognizable.
Commentary by Prof. Yuji Tsukii, Hosei University The organism is Vexillifera.
A hidden amoeba extends several slender pseudopodia from behind the end of one particle. As the amoeba comes to other particles, it extends pseudopodia from behind the one of particle. As the amoeba never shows itself completely, we cannot recognize where it is. In the meantime the amoeba and several particles begin journey to another place together with a colony of flagellates.
Commentary by Prof. Yuji Tsukii, Hosei University Two types of amoeba take turns appearing in this video.
Diaphoropodon is characterized by fine spiny projections on the surface of its shell, but to see these projections clearly requires higher magnification and resolution.
Diaphoropodon is characterized by fine spiny projections on the surface of its shell, but to see these projections clearly require higher magnification and resolution.
Diaphoropodon is characterized by fine spiny projections on the surface of its shell, but to see these projections clearly requires higher magnification and resolution.
An amoeba is gliding smoothly across the glass slide under the microscope. The rim of its body is transparent, but the center of its body is filled with food and slightly rigid. Although it doesn't extend pseudopods, food particles enter its body as the amoeba moves over them. A diatom is temporalily captured, but manages to escape.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is a species of testate amoeba called Cochliopodium.
The shell of this organism is like an upside-down plate, but as the shell is thin and transparent, its exact shape is difficult to see in ordinary observation.
When the organism detaches from the surface to float freely, the side view and shell shape become visible
The body of this moving amoeba seems a little stiff. Small flagellates are frequently scooped inside, but after struggling for a while, they get free. As the number of surrounding diatoms increases, they collide with the amoeba more and more often, causing it to change shape.
Commentary by Prof. Yuji Tsukii, Hosei University The shape and movements of pseudopodia are the keys to identifying naked amoeba.
This organism extends pseudopodia to attach itself to a glass surface,
but the effort is disturbed by a nearby diatom and ciliate.
Therefore, it is hard to identify its genus.
With its small body and lack of fibrous pseudopodia, this organism
may belong to medium- or small-sized group within the class Lobosea.
This oval amoeba has a slightly stiff body 70 microns long, and extends its numerous pseudopodia in all directions. Usually it is half-hidden inside the particle, but we can catch an occasional glimpse of the whole body before it disappears completely inside the particle.
Commentary by Prof. Yuji Tsukii, Hosei University The shape of this amoebae is greatly distorted because it has a lot of food in its cytoplasm. Amoebas are usually identified by their shape when moving. However in this video, it is difficult to determine not only the species but also to what group it belongs. The long extended pseudopodia are likely to be dactylopodia, but since many species of amoeba extend a similar type of dactylopodium, identifying this organism is also difficult even to the genus level. Similar types of amoeba are shown in the following links, but in addition to these amoeba, there may be other species which extend dactylopodia.
In a narrow space surrounded by particles, various microbes seem to be enjoying their lives. A flat leaf-shaped flagellate swims along, while a tiny amoeba without pseudopodia proceeds by pushing the front of its body forward as it contracts its rear end. A long filamentous algal colony and a variety of diatoms are all actively swimming around.
Commentary by Prof. Yuji Tsukii, Hosei University The organism that appears at the beginning and very end of this video may belong to a group related to Anisonema and Petalomonas, because it has a hard, flat body and a flagellum extending forward. It seems to be a rare species. However, we cannot be sure because the base of the forward flagellum is not clear, and we can’t confirm whether it has another flagellum at the posterior end.
The organism that appears during the middle part of this video may be Saccamoeba judging from its protoplasmic streaming and cell size. But it cannot be verified without examining the posterior end, which is not shown in this video.
In this view many aggregates are being pushed or pulled around by an amoeba and some diatoms. We can see an amoeba pulling one particle toward another, and finally many particles are connected together.
Commentary by Prof. Yuji Tsukii, Hosei University The organism in this video may be Saccamoeba. When amoebas are travelling, other particles often get stuck to the posterior end, which we can see in this video.
A transparent small amoeba changes it shape to squeeze into a particle. A tiny flagellate and diatoms are swimming around the edges of the screen.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is certainly a naked amoebae (without shell), but, it cannot be identified because its whole shape and especially the shape of its rear end cannot be seen clearly.
This small amoeba, about 30 microns long, is lying in a flat position in the center of the screen. Numerous particles can be seen inside its transparent shell. Some pseudopods start to appear at the edges of the shell, and then suddenly the amoeba rises up on the pseudopods and slowly moves to another place.
Commentary by Prof. Yuji Tsukii, Hosei University This video shows how an overturned Cochliopodium rights itself and begin to move again. It is a pity that we cannot clearly see the pseudopodia extending from under the shell. As this amoebae is relatively small and has a round shell, it may be Cochliopodium minus.
An amoeba about 70 microns in diameter is sitting still. It extends pseudopodia in all directions, but unlike the stiff axopods of Heliozoa, these pseudopodia are soft and thicker at the base. We can see numerous food particles inside the body.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is a testate filose amoeba called Gromia. In this video, only the shell is in focus. If the organism were completely in focus, we could probably observe its long, thin filopodia.
An amoeba 100 microns in length actively moves using its many slender pseudopodia. In the cytoplasm, we can see a contractile vacuole and numerous particles that were probably captured as food.
Commentary by Prof. Yuji Tsukii, Hosei University This is Vexillifera, a comparatively large amoebae. The shape and color of the cell body are similar to Mayorella, but unlike Mayorella, it extends several long, thin pseudopodia called dactylopodia.
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.
The sample was observed immediately after being collected from a paddy field.
As the body of this amoeba is completely transparent, it is difficult to find it among the surrounding aggregates.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is a kind of naked amoeba. To identify naked amoebae, it is necessary to know how they move. In this video, the surrounding aggregates block the view of the whole cell, which makes identification difficult.
It can be guessed from the video that the cell may be more than 100μm long and not quite flat, so this amoeba may belong to the suborder Tubulina.
At the top of the cell there is a transparent part without particles, called a hyaline cap.
It is unusual that, in spite of its large size, this cell contains relatively few large particles. Usually a large amoeba has many more small particles.
Is this amoeba really a large type and is the scale of this video correct?
After being collected from a paddy field, this sample was put on DNB agar plate (diluted nutrient broth with agar) with a drop of distilled water for 4 days, and then observed.
In this video an amoeba is surrounded by a lot of bacteria as it moves in several directions. The shape of the amoeba changes as the cytoplasm streams toward the direction of movement.
Commentary by Prof. Yuji Tsukii, Hosei University This naked amoeba belongs to genus Glaeseria.
Pseudopods in the genus Saccamoeba move straight forward along their axis line. However amoebae in the genus Glaeseria suddenly protrude semicircular pseudopods with a constriction at the base, after which the cytoplasm flows into the newly formed pseudopods. The key difference is that amoebae in the genus Glaeseria do not move in a straight line because their pseudopods are formed slightly off-center, causing them to go to the left or right.
Several long filamentous bacteria can be seen nearby.
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.
Soils from the L, H, and A layers were sampled from the Tohoku University Botanical Garden in Sendai. This is a video of an organism taken from the L layer on the soil surface, where there are freshly fallen leaves in their original shape and other organic debris. At first organisms could not be found in the newly collected soil, so the samples (including water) were left for one month and then observed.
Commentary by Prof. Yuji Tsukii, Hosei University This organism is a type of amoeba called Vannella miroides. Its flexible shape allows it to maneuver
through obstacles.
