Sessile Rotifers?

[Katfisch]

https://photos.app.goo.gl/8H2a7L6B79xWGUnq7

[sinabro]

Hi Katfisch...
Good result. it's epistylis

[Katfisch]

Thanks, sinabro!
I was confused by the lack a visible stalks, and as a novice, I’ve been seeing a lot of Rotifers of various sizes and morphologies.
This colony of Epistylis was attached to a dead crustacean carapace, as they apparently like to do.
I was amazed at the volume of water they were moving.

[Bruce Taylor]

Hi Katfisch...
Good result. it's epistylis

Epistylis typically has a long, clearly visible stalk. These are more likely to be Scyphidia or Rhabdostyla, both of which can be epibionts on crustaceans. The former has no stalk, the latter has a very short one. We don't clearly see how the cells are attached to the substrate, so I don't think we can identify below order: Sessilida.

[sinabro]

Hi Katfisch...
Good result. it's epistylis

Epistylis typically has a long, clearly visible stalk. These are more likely to be Scyphidia or Rhabdostyla, both of which can be epibionts on crustaceans. The former has no stalk, the latter has a very short one. We don't clearly see how the cells are attached to the substrate, so I don't think we can identify below order: Sessilida.

I am always surprised by your knowledge. Thanks Bruce...

[Bruce Taylor]

I am always surprised by your knowledge. Thanks Bruce...

And I'm always surprised by the amazing clarity of your microscopy! (as in your videos of Haematococcus & ciliates)

[Katfisch]

Bruce,
I'm thinking (and I hope correctly) Scyphidia because of a peak in the center of the disc.
I'm a bit disappointed with my iPhone videos that don't do justice to the details I'm seeing through the oculars.

[Bruce Taylor]

To identify your critters to family level, you'd begin by determining whether they have a stalk, or adhere to their host by means of an organelle called a "scopula." If the former, they are in Epistylidae; if the latter, Scyphidiidae. To get down to genus, after that, it might be necessary to rule out a few other members of the respective families (Paravorticella, Apiosoma, etc.)

It's not clear to me what you mean by "disc." Are you referring to the scopular attachment at the base of the cell?

[Katfisch]

By disc, I meant the ciliated disc (peristome?).
Sorry for the nomenclature confusion on my part.
(I’ve got Hegner’s INVERTEBRATE NOMENCLATURE on order)

[Bruce Taylor]

The terminology can be baffling. Yes, "peristome" is a handy word for the whole area around the mouth.

I don't think a "peak" in the oral region is a diagnostic character for Scyphidia. Some sessile peritrichs do have specialized structures called "opercula" (little caps or flaps, which can be roughly disc-shaped), but scyphidiids don't have these.