River diatoms and "bubbles"

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Hobbyst46
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River diatoms and "bubbles"

#1 Post by Hobbyst46 » Fri Apr 10, 2020 10:59 pm

Hi All,
Health and safety to everyone.

A week before the corona lock-down I collected a live diatom sample from a small polluted local river. As expected, most diatoms were pennales and the variability was poor. Nevertheless, I cleaned them with APS* and home-grade hypochlorite, and managed to prepare a few Pleurax strew slides. In spite of my sloppy preparation and plenty of debris, diatoms could be clearly observed. I inspected them with the following objectives : 40X/0.75 phase contrast (PC) dry, 40X/0.8 (iris) oil darkfield (DF), 100X/1.3 Planapo PC (oil), 100X/1.25 achromat (oil) sort-of-DF. The ultracondenser (oil) was used for DF. Images were taken with the afocally-installed mirrorless, except for DF which were taken with an eyepiece camera.

I always start a diatom session by phase contrast; at 40X or 100X PC it is fun (see photo 1 for an example), and well worth the trouble of the oil immersion. Diatom lengths were mostly 15-50 um. Due to the gentle cleaning, many diatoms remained fairly intact (photos 2 & 3), although some were broken into valves and girdles. Diatoms that appear much brighter and more colorful than others are, I believe, intact frustules. Others might be just valves. Photo 2 shows two diatoms (Naviculas?), that are mutually aligned, perhaps owing to the shape of their outer surfaces, or maybe they are actually a single "thick" frustule ??

I noticed a circle, an air bubble - what else could it be? (Photo 4, PC). Then another circle appeared (photo 5, DF), and another. Strangely enough, they are all about the same diameter - 15-20 um. Such uniform air bubbles?. Switched the slide for another and tried BF with the 40X dry (photo 6, middle). Now that is not a bubble, but a short transparent open tube. Tried oblique (photo 7) - it is a transparent shallow cylindrical container. And the same conclusion from another (photo 8, BF). Later, I found one that was lying on its side (photo 9, DF). And, just very few so far, I found the valve (perhaps still part of the intact frustule) of Cyclotella meneghiniana Kutzing**.

* APS cleaning is less hazardous than many literature procedures, but appropriate precautions and laboratory safety measures are mandatory.
** Identification is based on an atlas of local diatoms.

So, several illumination modes can help to answer a question.

Comments are welcome.
Attachments
(1) 100X PC.jpg
(1) 100X PC.jpg (92.47 KiB) Viewed 1716 times
(2) Two separate diatoms or one. Stack of 5. 100X PC. Cropped.jpg
(2) Two separate diatoms or one. Stack of 5. 100X PC. Cropped.jpg (56.61 KiB) Viewed 1716 times
(3) Surirella ovalis Brebisson. STack of 5. 100X PC. Cropped.jpg
(3) Surirella ovalis Brebisson. STack of 5. 100X PC. Cropped.jpg (22.57 KiB) Viewed 1716 times
(4) Suspected air bubble -or else. 100X PC.JPG
(4) Suspected air bubble -or else. 100X PC.JPG (57.45 KiB) Viewed 1716 times
(5) Suspected air bubble - or else. 100X DF.jpg
(5) Suspected air bubble - or else. 100X DF.jpg (44.47 KiB) Viewed 1716 times
Last edited by Hobbyst46 on Fri Apr 10, 2020 11:04 pm, edited 1 time in total.
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Hobbyst46
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Re: River diatoms and "bubbles"

#2 Post by Hobbyst46 » Fri Apr 10, 2020 11:02 pm

(continued)
Attachments
(6) Suspected circle. 40X BF.JPG
(6) Suspected circle. 40X BF.JPG (59.6 KiB) Viewed 1715 times
(7) Cylindrical transparent container. 40X oblique.JPG
(7) Cylindrical transparent container. 40X oblique.JPG (59.62 KiB) Viewed 1715 times
(8)  Cylindrical transparent container. 40X BF.JPG
(8) Cylindrical transparent container. 40X BF.JPG (60.84 KiB) Viewed 1715 times
(9) Cylindrical transparent container on its side. 100X DF. Cropped.jpg
(9) Cylindrical transparent container on its side. 100X DF. Cropped.jpg (10.42 KiB) Viewed 1715 times
(10) Cyclotella meneghiniana Kutzing. 100X PC.JPG
(10) Cyclotella meneghiniana Kutzing. 100X PC.JPG (57.49 KiB) Viewed 1715 times
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MichaelG.
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Re: River diatoms and "bubbles"

#3 Post by MichaelG. » Fri Apr 10, 2020 11:07 pm

Later, I found one that was lying on its side (photo 9, DF)
Excellent ... Congratulations !!

MichaelG.
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MicroBob
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Re: River diatoms and "bubbles"

#4 Post by MicroBob » Sat Apr 11, 2020 5:18 am

Hi Doron,
nice catch!
Could these cylinders be the girdle bands of centrales diatoms? So valves and circular objects match in numbers so this could be true?

Bob

Hobbyst46
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Re: River diatoms and "bubbles"

#5 Post by Hobbyst46 » Sat Apr 11, 2020 10:44 am

Thanks, MichaelG and MicroBob!

Bob, I indeed believe that the cylinders are top-valve-less Cyclotella frustules. So photo 9 is a girdle view and photo 10 is the top valve view. Possibly, the cleaning procedure, gentle as it was, removed the top valve from the frustule. Statistically, there should have been the same number of girdles as valves, but I do not have enough evidence for this, because the corona lock-down is preventing me from making more slides. In the existing 2-3 slides, I only found one Cyclotella valve and very few valve-less frustules.
Cyclotella are incredibly complex structures, as seen by SEM. A short literature survey showed me that there are many descriptions of the valves, but very few girdle views.
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Re: River diatoms and "bubbles"

#6 Post by DonSchaeffer » Sat Apr 11, 2020 11:03 am

I'm awe inspired.

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75RR
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Re: River diatoms and "bubbles"

#7 Post by 75RR » Sat Apr 11, 2020 11:56 am

One of these days I am going to get around to making a strew slide.

Only thing stopping me is the amount of work involved. ;)

Nice work!
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Hobbyst46
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Re: River diatoms and "bubbles"

#8 Post by Hobbyst46 » Sat Apr 11, 2020 1:24 pm

Many thanks 75RR.
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MichaelG.
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Re: River diatoms and "bubbles"

#9 Post by MichaelG. » Sat Apr 11, 2020 1:25 pm

Hobbyst46 wrote:
Sat Apr 11, 2020 10:44 am
Cyclotella are incredibly complex structures, as seen by SEM.
Most definitely

https://www.sciencephoto.com/media/8745 ... diatom-sem
https://naturalhistory2.si.edu/smsfp/ir ... hryso1.htm

What worries me a little, though, is that they generally seem to be much lower-profile than what you show

I am quite ignorant of these things, so ... can anyone nominate a species with the 'Hobbyst46' aspect-ratio ?

MichaelG.
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Hobbyst46
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Re: River diatoms and "bubbles"

#10 Post by Hobbyst46 » Sat Apr 11, 2020 3:58 pm

MichaelG. wrote:
Sat Apr 11, 2020 1:25 pm
What worries me a little, though, is that they generally seem to be much lower-profile than what you show

I am quite ignorant of these things, so ... can anyone nominate a species with the 'Hobbyst46' aspect-ratio ?
Thanks for the comment, Michael!
In the Atlas there were only valve views, but as Fortuna struck I just found this beautiful source:
Nordic Microalgae
http://nordicmicroalgae.org/taxon/Cyclo ... neghiniana
They provide rich data and a table that gives sizes and aspect ratios. It appears that "my" aspect ratio" of ~0.83 is OK for this species.
Apparently the aspect ratio varies from species to species. Good to know!
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Re: River diatoms and "bubbles"

#11 Post by MichaelG. » Sat Apr 11, 2020 5:15 pm

Hobbyst46 wrote:
Sat Apr 11, 2020 3:58 pm
I just found this beautiful source:
Nordic Microalgae
http://nordicmicroalgae.org/taxon/Cyclo ... neghiniana
They provide rich data and a table that gives sizes and aspect ratios. It appears that "my" aspect ratio" of ~0.83 is OK for this species.
Apparently the aspect ratio varies from species to species. Good to know!
Brilliant find ... Thank You

MichaelG.
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Hobbyst46
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Re: River diatoms and "bubbles"

#12 Post by Hobbyst46 » Sat Apr 11, 2020 6:52 pm

Thanks DonShcaeffer !
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Re: River diatoms and "bubbles"

#13 Post by Hobbyst46 » Sat Apr 11, 2020 8:06 pm

Could not resist adding another diatom, Nitzschia, which I managed to identify.
Attachments
(11) Nitzschia sigma. Stack of 4. 100X PC. Cropped.jpg
(11) Nitzschia sigma. Stack of 4. 100X PC. Cropped.jpg (33.62 KiB) Viewed 1574 times
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Re: River diatoms and "bubbles"

#14 Post by daruosha » Sat Apr 11, 2020 11:33 pm

Very nice and inspiring shots Hobbyst46.
Daruosh.

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Re: River diatoms and "bubbles"

#15 Post by Hobbyst46 » Sun Apr 12, 2020 5:29 am

Thanks daruosha!
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Re: River diatoms and "bubbles"

#16 Post by 75RR » Sun Apr 12, 2020 6:19 am

That is a nice image of a Nitzschia

Have you tried to image diatoms using COL?

Would be nice to see a same subject comparison with Phase/COL
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Re: River diatoms and "bubbles"

#17 Post by Hobbyst46 » Sun Apr 12, 2020 8:54 am

75RR wrote:
Sun Apr 12, 2020 6:19 am
That is a nice image of a Nitzschia

Have you tried to image diatoms using COL?

Would be nice to see a same subject comparison with Phase/COL
Thanks. Will try.
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Hobbyst46
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Re: River diatoms and "bubbles"

#18 Post by Hobbyst46 » Wed Apr 15, 2020 8:41 pm

75RR wrote:
Sun Apr 12, 2020 6:19 am
That is a nice image of a Nitzschia

Have you tried to image diatoms using COL?

Would be nice to see a same subject comparison with Phase/COL
Tried it with three different diatoms. Could not find my original nice Nitzschia (forgot to document the location on the slide... :x ) so
here are others, two Naviculas and a different Nitzschia. Identifications are tentative, might be wrong.
All were imaged with the 100X1.3 oil Ph3 objective. Oblique was done by displacing the condenser from the phase 3 position.
All photos are single images.
Phase contrast images were slightly brightened in post-p, then resized and cropped.
Oblique images were brightened, contrast was enhanced, then resized and cropped 9all crops by ~2X in each direction).
Attachments
Navicula geoppertina (32um) phase contrast.jpg
Navicula geoppertina (32um) phase contrast.jpg (74.35 KiB) Viewed 1480 times
Navicula geoppertina oblique.jpg
Navicula geoppertina oblique.jpg (77.22 KiB) Viewed 1480 times
Navicula recens (48um) phase contrast.jpg
Navicula recens (48um) phase contrast.jpg (74.4 KiB) Viewed 1480 times
Navicula recens oblique.jpg
Navicula recens oblique.jpg (105.86 KiB) Viewed 1480 times
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Hobbyst46
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Re: River diatoms and "bubbles"

#19 Post by Hobbyst46 » Wed Apr 15, 2020 8:42 pm

Continued.

note: the transparent "square" form near the bottom end of the Nitzschia is a frustule of Cyclotella (minus a valve), lying on its side, as described in the post above.
Attachments
Nitzschia sp. (82um) phase contrast.JPG
Nitzschia sp. (82um) phase contrast.JPG (69.31 KiB) Viewed 1477 times
Nitzschia obliqu.JPG
Nitzschia obliqu.JPG (112.33 KiB) Viewed 1477 times
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Wes
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Re: River diatoms and "bubbles"

#20 Post by Wes » Wed Apr 15, 2020 8:56 pm

Amazing stuff. Thanks for posting, in fact this got me inspired to go the local canal and take a bit of brown scum which was chock full of diatoms.

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