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Diatoms and algae playmates?

One by one numerous diatoms approach a long chain of algae that is moving in a leisurely arc. Sometimes the diatoms snuggle against and push or poke the algae, but the algae chain continues its journey as if it doesnt care.

Commentary by Prof. Yuji Tsukii, Hosei University
This blue-green alga belongs to genus Oscillatoria.

Many species are included in genus Oschillatoria, and their identification is tricky.

But judging from the unique shape of this organism, it might be Oschillatoria jovis.

The cell-size of O.jovis is reported to be 3.4~4.2μm in width, and if the width of this organism is similar, the organism is likely to be O.jovis.

The diatoms passing by Oschillatoria might be a species of genus Navicula, but this is difficult to determine because there are so many small diatoms with a similar appearance.

Diatoms are usually difficult to identify without observing their shell pattern using a scanning electron microscope or a high-resolution optical microscope. To do this, it is necessary to remove cell material from the shell through a chemical process.

Sampling Date : 08 August 2009

Sampling Site : Hirose River A  Google Map

Journey of blue-green algae

Twelve cells are connected like a chain. They slowly begin their journey to another place despite the lack of any specialized moving apparatus. Where are they going and why?

Commentary by Prof. Yuji Tsukii, Hosei University
This organism is definitely a blue-green alga belonging to the genus Oscillatoria.

Its classification into species is difficult because the genus Oscillatoria includes so many species. Using the Illustrated Book of Japanese Fresh-Water Algae (1977), there are two species that are most likely to match the one in this video. Both of them are made up of long chains of cells characterized by narrow “waists” where two cells connect, and round tips at both ends of the chain. The blue-green cells of one species, Oscillatoria iwanoffiana, are 5~9μ in width and have a pseudo-vacuole within each cell.

The cells of another species, Oscillatoria jovis, are 3.4~4.2μ in width and seem to be homogeneous.

If the width of the trichome (chain of cells) and its inside view (whether cytoplasm is homogeneous or includes a pseudo-vacuole) are clearly observed, we may classify these organisms according to the above reference book. However, we cannot dismiss the possibility that new species have been identified since its publication is in 1977.

Sampling Date : 09 August 2009

Sampling Site : Hirose River B  Google Map

A still-life view of algae and diatoms

This is a tranquil scene featuring various kinds of diatoms and green algae, none of which is moving.

Commentary by Prof. Yuji Tsukii, Hosei University
The organism in this video is not green algae but a diatom.




The two long green organisms in the central part of the figure are Oscillatoria

A small Scenedesmus can be seen between Synedra and Oscillatoria.

Sampling Date : 18 October 2009

Sampling Site : Hirose River A  Google Map

Algal cells among particles

A long colony of green algal cells is rigidly connected, resembling a pole. It moves in a straight line, either forward or backward, toward a particle. Another type of individual green algal cell is half-hidden behind the particle. A Euglena cell is attached to the particle and does not move. There are numerous unmoving diatoms surrounding the particles.

Commentary by Prof. Yuji Tsukii, Hosei University
Closterium acerosum is half visible behind a black particle

Oscillatoria is approaching the particle from the lower right side.

Its trichome is narrow, cell length is short, and there are no visible particles in the septum between cells. Based on these features, the organism may be Oscillatoria simplicissima.

But to conclusively state that the organism is Oscillatoria simplicissima, it is necessary to measure the width of its trichome, length of each cell, and to confirm the absence of any particles in the septa.

Sampling Date : 18 October 2009

Sampling Site : Hirose River A  Google Map

Diatoms seem to play with green algae

A long colony of light-green algal cells proceeds in a straight line. Numerous diatoms accompany the algae on its journey, playfully interacting with it, even attaching themselves and riding it like a conveyor belt. Some diatoms are also connected with each other in chains. Diatoms seem to benefit from these connections to move around from place to place.

Commentary by Prof. Yuji Tsukii, Hosei University
The title of this video is incorrect.

This organism is not green algae but a blue-green algae named Oscillatoria.

Since its cell size is not so large as that of O. princeps or O. limosa, the organism is probably one of the following smaller species:

O. irrigua, O. simplicissima or O. agardhii

Sampling Date : 18 October 2009

Sampling Site : Hirose River A  Google Map