Striatella unipunctata

[75RR]

Zeiss Planapo 63x/1.4, DIC, 145µm width, 2 stacks stitched in Photoshop, Marine sample, Alboran Sea

Same slide as Actinocyclus sp.
.

[75RR]

Detail at 100%

[Beatsy]

Thanks for the detail shot. You've *just* got the punctae resolved in a few spots. Miniliform, at least. Any idea on their spacing?

[75RR]

Large square is 10µm and small one is 1µm
Drawn in Illustrator, lines are 0.5 point. Image is screen shot.
.

[75RR]

Following Beatsy's query on resolution, I looked for some SEM images of Striatella unipunctata in order to see what there was was to be seen
Page 92 Fig. 5-d (see link below) would seem to indicate that the beading is perhaps more of an artifact than not.

https://www.researchgate.net/publicatio ... nskoe_mora

[Scarodactyl]

That's a location on your hard drive, not a link.

[75RR]

That's a location on your hard drive, not a link.

Corrected. Thanks

[rjlittlefield]

Following Beatsy's query on resolution, I looked for some SEM images of Striatella unipunctata in order to see what there was was to be seen
Page 92 Fig. 5-d (see link below) would seem to indicate that the beading is perhaps more of an artifact than not.

https://www.researchgate.net/publicatio ... nskoe_mora

I am not sure what "beading" and "artifact" mean. The railroad-track structure that I see in figure 5-d looks qualitatively like what I see in your images. But there is a significant scale difference, about 4 railroad-ties per micron in the paper versus 2 ties per micron in your marked up illustration. This is judging from the scale indicators in both cases. My mind volunteers the possibilities that one or another scale indicator is wrong, or the subjects really do have 2X variation in element spacing, or these are not comparable elements. My mind does not feel good about the possibility that the optical imaging process somehow halved the density of ties while still producing such definite structure in the image.

Can you say more about what you're thinking?

--Rik

[75RR]

The railroad-track structure that I see in figure 5-d looks qualitatively like what I see in your images. But there is a significant scale difference, about 4 railroad-ties per micron in the paper versus 2 ties per micron in your marked up illustration.

I agree. I am going to assume it is my calculations that are off. Will check tomorrow.

[75RR]

The railroad-track structure that I see in figure 5-d looks qualitatively like what I see in your images. But there is a significant scale difference, about 4 railroad-ties per micron in the paper versus 2 ties per micron in your marked up illustration.

I agree. I am going to assume it is my calculations that are off. Will check tomorrow.

Beading referred to Beatsy's mention of 'Miniliform' and my mention of 'artifact' was due to the SEM not appearing to show beading.

It was a curious scale difference, so much so that I rechecked my calculations based on my Stage Micrometer just in case.
That left a misreading on my part when I measured the diatom, or differences in scale of 'railroad tracks' based on diatom size.
While having a look at fig 5-d it occurred to me to check the scale on figure 5-c as well to see if there was an appreciable variation.

See screen shot below with 1µm squares superimposed on figures 5-d and 5-c
.

[rjlittlefield]

See screen shot below with 1µm squares superimposed on figures 5-d and 5-c

Fascinating! Apparently the same structures, in the same paper, but with 2X difference in density ("ties per micron").

On quick search of the paper, I can find reference to those illustrations at only one place, which says only "The axial field is linear, with an axial rib (Fig. 5c, d)". I cannot see anything in the text that specifically refers to the size of these structures.

I note also that the scale bars in Fig 5 appear in a variety of positions and orientations, which suggests to me that they were manipulated by some human process.

Taking all this together, I find that my usual faith in SEM scale bars has been eroded in this case. I would not be surprised if the 5d scale bar is simply wrong.

Do your pictures indicate that there should be any big difference in spacing of the "railroad ties" between the locations shown in 5c and 5d?

--Rik