Another ciliat from a little stream between two lakes!

[KD Arvidsson]

Darkfield. Magnification 40-100 x. Could it be a Prorodon? Very difficult to film //KD

https://youtu.be/ygz_e8Drnpk

[daruosha]

Crisp and well illuminated. Nice video KD.

I suggest try different size dark field patch stop disks for optimum depth of field and background darkness. I guess the last microorganism in the video is a Paramecium.

Congrats for yet another beautiful footage.

[KD Arvidsson]

Hi Daruosha Thank you for comment. I like constructive criticism very much I have bought a collection of 36 different Rheinberg filters i experimenting with Some of them are useless and some are great Do you know what the filter should look like to increase the DOF Daruosh?//KD

[daruosha]

In my experience, closing the field iris a bit and using bigger patch stop disks yields a more DOF in the final image. Adjusting condenser height also helps better contrast.
In case of your microscope, make hole on a cardboard and put in on top of the light assembly. Try different hole sizes and use the one which is just big enough to cover the eyepiece field of view.

[KD Arvidsson]

Thank you Daruosh I will try this //KD

[Bruce Taylor]

Could it be a Prorodon?

There's a lot of confusion about Prorodon, because most species previously included in that group actually belong in Holophrya (and were formally moved there by Wilhelm Foissner, in a paper that appeared just weeks before his death earlier this year). Prorodon as currently defined, consists mostly of species formerly placed in Pseudoprorodon! This is the kind of mixup that gives taxonomists a bad reputation.

Anyway, this doesn't appear to be either Holophrya or Prorodon, because we don't see anything like a mouth at the anterior pole of cell. We glimpse the mouth briefly at a couple of points -- it's quite far forward, on the side of the cell. However, we don't clearly see the shape, and can't make out many other diagnostic features. Dark field microscopy isn't great for ciliate identifications, usually. It can be handy for showing the macronucleus, which in this ciliate is sausage-like.

Ophryoglena is likely, given the shape of the cell & macronucleus, the rotating motion, and the location of the cytostome. However, I'd want to inspect the mouth more closely, to be sure.

Nice video!

[KD Arvidsson]

Thank you Bruce! I see it is very complicated but very interesting. Please can you take a look of another film from yesterday! (Lunarface in microcosmos) could it be a Prorodon S.p?? It is only a documentation so the quality is not so good! //KD

[Bruce Taylor]

OK, I watched it. Again, we don't see the mouth in that video, so identification is not possible. Prorodon (=Pseudoprodon sensu Kahl), would have a mouth at the anterior pole of the cell, and a long, wormlike macronucleus. The mouth (cytostome) is supported by a palisade of cytopharyngeal rods (nematodesmata)...often fan-shaped, wider at the anterior.

[KD Arvidsson]

Thank you very much Bruce! Mouth is very important to identify prorodon complex. I will do my best to film the mouth next time i find this creature //KD

[Bruce Taylor]

Mouth is very important to identify prorodon complex.

Mouth is important for most ciliate identifications. Usually, it is the first feature you should look for. Other useful characters are the arrangement of somatic cilia (or cirri, as the case may be), the shape of the macronucleus, location and number of contractile vacuoles, presence/absence of symbionts and/or cortical pigments, and extrusomes (trichocysts). With sessile peritrichs, it's important to record the stalk.

[KD Arvidsson]

Thank you Bruce again!! //KD