Freshwater Algae mix

[Tardigrade37]

Here are a few shots of algae taken from local ponds and swamps.

First image is detail of a Micrasterias desmid.



Second is an unusual view of the desmid Spirogyra.



Lastly is ?? The only thing I can find similar to this colonial alga is cyanobacteria, but I am pretty confident that this is a true alga. Anyone have any ideas?



Chris

[Wim van Egmond]

Very nice, that is a Micrasterias that I have never seen. Where did you find it?

The bottom image is of cyanobacteria; Merismopedia.

Wim

[Tardigrade37]

You have a very good eye Wim. I have tentatively identified this as Micrasterias radiata, but it is not well documented. It was collected in a sphagnum sample near my home in Massachusetts.



Thanks for the ID on the last one! I was leaning away from Cyanos because I think that I can clearly see chloroplasts, but perhaps I am mistaken.

Chris

[BJ]

hi Chris,

I do not think that your second photo is of Spirogyra as it looks as though the green structure is on the outside. The large "cell" is perhaps the empty shell (exuvia) of a crustacean perhaps a copepod.

When I first looked at your last photo, I too thought it was the cyanobacterium Merismopedia as Wim has suggested, because of the sheet of similar cells. However, looking more closely, I agree with you that it looks like a true alga, as there are clear structures (organelles) within the cells. Also there is a suggestion that the cells are in groups of 4.

I think that it is green alga either in the genus Crucigenia or Crucigeniella, with my best guess Crucigeniella irregularis. One would normally dismiss these two genera looking at photos/drawings in a guide as the usual condition illustrated is a colony (coenobium) of just 4 cells quite tightly arranged. What I think you have is a large colony made up of many 4-celled groups....this is called a syncoenobium.

regards
Brian

[Marek Mis]

Chris,

Your Micrasterias and Merismopedia are very nice. What kind of optics do you use ? And what magnification was in your photographs (what objectives) ?

Regards
Marek

[Wim van Egmond]

Indeed, I don't think Merismopedia has such chloroplast-like structure.

But that second one could be Spirogyra but extremely flattened and therefor distorted.

I am curious if we can find the right answers.

Wim

[Franz Neidl]

The second alga is looking like a oogonium from Oedogonium (O. capillare?).
But this is rather my suspect. Where are the specialists?

Franz

[BJ]

Hi,

second thoughts on the Spirogyra......

are we looking at the cell and chloroplasts through an air bubble?

Even if this is so, the outline of the chloroplast is very ´blebby´ ....is it plasmolysing?

Probably a completely different idea from me in an hour

regards
Brian

[Tardigrade37]

Thanks all for the comments. When I get home tonight, I will post additional pictures of the putative Spirogyra and Merismopedia-like organism. I recall that the latter was in very large ruffled sheets (visible with the naked eye, probably 1-2mm or so), and it was quite difficult to tease off a small enough portion to get a flat image.

I also will be able to post details of the images including scale bars. If I recall correctly, they were all shot with a 63x/1.40 Plan-Apochromat lens with DIC. The second Micrasterias image is the exception - DIC with a 20x/0.5 EC Plan-Neofluar lens.

Regards,
Chris

[Tardigrade37]

Hi,

second thoughts on the Spirogyra......

are we looking at the cell and chloroplasts through an air bubble?

Even if this is so, the outline of the chloroplast is very ´blebby´ ....is it plasmolysing?

Probably a completely different idea from me in an hour

regards
Brian

Hi BJ,

This was definitely not shot through an air bubble, but the cells were not very happy at this point. The culture had gone from a very rich green color to a semi-translucent yellow-green color. The chloroplasts had clearly shrunk to an unhealthy size and my initial suspicions was that his cell was caught in the process of dividing when culture conditions deteriorated.

Regards,
Chris

[Tardigrade37]

Here is the Spirogyra in a happier state.



Here is another shot of the colonial alga showing the large sheet-like growth.

[BJ]

Hi Chris,

I´ve just made it to my books, and i have some more thoughts for you:

1. the sheet of cells. Looking at your second shot which shows the same degree of cell organisation across such a distance and with your observation that the original specimen was 1 -2 mm , I think we can dismiss my idea of Crucigenia/Crucigeniella. They might form colonies of a few hundred cells, but not this big. The clear ´mucilage´ between the cells may be an important clue.

My current suggestion is it may be a fragment of Monostroma bullosum. I have seen some marine species of this genus, but not any freshwater specimens. Apparently M.bullosum tends to have cells in groups of 4.

I have managed to find just one publication with a photo of the cells of this species :-

http://www.springerlink.com/content/x28 ... lltext.pdf

2. I have an encyclopedic taxonomic reference on Spirogyra

"The Zygnemataceae" by EN Transeau (1951).

236 pages + 41 plates.

Many of his illustrations show bulging cells like yours (unfortunately not with much detail - just outline drawings - sometimes with the chloroplasts shown). In nearly every case these bulging cells are involved in reproduction. Either producing an asexual akinete or aplanospore or forming a gametangium which will eventually lead to the production of a sexual zygospore through conjugation. In each case the chloroplasts become rather disorganised.

As you say it does look as if the cell is just dividing, perhaps they would have gone on to produce two adjacent gametangia?

Thanks for great photos and getting me thinking!

regards
Brian

[René]

Hi Brian, I think you're getting to far out. I admit the DIC effects of the sheets of cells throw me off somewhat as well, but the creasing of the cells might be to do with the age/condition of the cells. Unless I see other proof (lugol staining for starch/pyrenoids, nuclear staining), I would regard it as Merismopedia.

Best wishes, Rene