Diatoms from the Seychelles!

[MicroBob]

Hi together,
yesterday I had a look at a couple of diatom slides and found an interesting one from the Seychelles. I didn't wan't to touch the oil resources so used the Zeiss Jena 40 / 0,95 dry Apo. Here I will show some better snapshots.
The slide contains objects that I would ithink of as pollen so organic material might be present.
The first one might be a Cocconeis alucitae corrected:Climacosphenia elongata. I will post some more.

Bob

[Hobbyst46]

Very nice catch, Bob!
Impressive use of the dry 40X0.95.
Please details about illumination, mounting media (or is it air?), darkfield condenser.

I myself found some diatoms quite like your long one with rectangular "windows" in the shore mud of the Mediterranean Sea recently, but did not make permanent slides yet.

[75RR]

Very nice image, like how it shows off the variety and detail. Great ad for diatoms.

Long diatom running left to right looks like the valve view of a Licmophora




viewtopic.php?t=7839

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[MicroBob]

Hi Doron,
this was mounted in Naprax, no idea how the material was cleaned, for sure no harsh acid cleaning. Image taken with Zeiss DIC "old". When everything fits perfectly one gets a kind of darkfield look. With the Zeiss Jena 40/0,95 I only get a black strip which I can place as best as possible, so I always have a gradient in the image. All images are stacked from 20-40 single shots with Picolay.
The old Phomi with it's Optovar has a tube factor of 1,25x, 1,6x or 2x. So the image is always at least 12,5x post magnified with 10x eyepieces. This makes high aperture objectives useful. Without the Optovar I didn't see as much use in this objective. With the Phomi it is useful for quick scanning of slides with fine detail. Among the slides I looked at were several quite boring ones and it would have been a lot of work to clean them from oil after a short look.

@ Glen,

I got the identification from this document: https://micronesica.org/sites/default/f ... final2.pdf and the image of Cocconeis alucitae corrected:Climacosphenia elongata fits quite well. The outer shapes of Licmophora drawing look similar, but they don't seem to have these internal compartments. Your linked image in contrary shows a diatom that is very similar to the one I posted here. Maybe your fresh diatom was a Cocconeis corrected:Climacosphenia elongata too? This would for sure be a nice object for a SEM!

Here comes the next diatom, probably girdle band view and of a very interesting shape. Do you have an ID for this one, Glen?

Bob

[75RR]

Thanks for the link - useful to have.

I have to agree that it is not Licmophora (I am still in shock) but neither is it Cocconeis

Note that the plate numbers are above the image, not below. That would make it plate 6

See link below for confirmation

So looks like it is: Climacosphenia elongata

https://pubs.usgs.gov/of/2012/1163/page ... Azores.pdf


Update: Have now been able to confirm that the diatom in my first link viewtopic.php?t=7839 is Climacosphenia moniligera :)

[MicroBob]

Thank you for pointing this error out! I have corrected it in the text. The formatting of my ID resource is not too clear and I connected the wrong description to the right image. But at least this new ID should be close to spot on.

[75RR]

Here comes the next diatom, probably girdle band view and of a very interesting shape. Do you have an ID for this one, Glen?



Bob

I think it might be a Biddulphia

possibly Biddulphia capusina or Biddulphia tridens: https://www.oamarudiatoms.co.uk/gallery_302510.html

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[MicroBob]

Hi Glen,
thank for the ID and the link!

Here one more in diagonal orientation, Anne from the german forum names it Biddulphia pulchella.
Diatoms are a bit like architecture - once you have grasped the general concept it becomes understandable. I have not yet reached this state with diatoms...
I recently came to proper ID literature at least for european diatoms!

Bob

[75RR]

Diatoms are a bit like architecture - once you have grasped the general concept it becomes understandable.

It would be nice to have 3D representations of some of them.

[KurtM]

Interesting thread, great images, really like the oblique view!

Yes, getting a look at a variety of angles is hugely helpful to understanding the architecture of these fascinating forms! Here's an article I found pretty interesting on the very subject:
https://tinyurl.com/u5bchhq

[75RR]

Here's an article I found pretty interesting on the very subject:
https://tinyurl.com/u5bchhq

Many thanks for the link. Impressive work.

[MicroBob]

Yes, getting a look at a variety of angles is hugely helpful to understanding the architecture of these fascinating forms! Here's an article I found pretty interesting on the very subject:
https://tinyurl.com/u5bchhq

Hi Kurt,
thank you for this link! The comparative views are really interesting. And all these shapes will have a function for the algae!

Here another image, probably again a Biddulphia in frustule view.

Bob

[MichaelG.]

Thanks for the link, Kurt
... a very informative article.

MichaelG.

[mrsonchus]

Must agree, not my area as they say, but really interesting images and the link is to a very readable (for such as myself with no Diatom knowledge at-all) and interesting article!
As mentioned, the variety of forms must surely be a response to optimal requirements in one way or another - clearly a fascinating subject when the surface is scratched!