Urosoma?

[janvangastel]

I found a very nice hypotrich again. It is about 270 microns long and very flexible. I did not see rows of cirri like Uroleptus has, only some cirri close to the tail part. It was bnot easy to catch on video. It seems to have yellow or 'gold' colored algae in its protoplasma, but it might as well be other stuff then algae. I spend a lot of time to try to ID it, but I couln't decide. It looks mostly, to my untrained eye, like Urosoma Cienkowsky, which might be the same species as Uroleptus rattulus, according to Kahl.

[KD Arvidsson]

Great clip Jan as always

[Bruce Taylor]

Great observation! I think Urosoma is a reasonable identification, mostly because the oral area is "Gonostomum-like" (i.e undulating membranes follow the adoral membranelles on the left side of the cell, so we don't see the question-mark pattern that is common among hypotrichs). We don't see all somatic cirri, but transverse cirri are briefly visible at 0:19, and we catch a glimpse of left and right marginal rows, as well. So, a very flexible cell, tapering to a posterior tail, with 2 macronuclear nodules and paroral structures in the Gonostomum pattern. Urosoma cienkowski is reasonable, but that species now considered a junior synonym of Urosoma caudata. Here's an excellent redescription of the species, with good measurements and images: https://onlinelibrary.wiley.com/doi/epd ... /jeu.12756 Your specimen surpasses the maximum length the authors give for the size of the species in their Chinese population, but is within the range given for populations recorded by earlier European researchers.

[janvangastel]

Interesting article Bruce, thanks for the link. So it is probably Urosoma caudatum.
Thanks KD.

[Bruce Taylor]

Here's another interesting detail, which confirms the genus as Urosoma. Your ciliate has four ring-shaped structures called "lithosomes" distributed in the cell, as shown in the modified image below.

Lithosomes.JPG (26.08 KiB) Viewed 2273 times

They might easily be mistaken for food vacuoles but their location doesn't shift or circulate in the cytoplasm. See the article I cited above, and this one: https://www.sciencedirect.com/science/a ... 3919300987.

Reading about lithosomes sent me back to look at a ciliate I recorded a long time ago. And, sure enough, they are visible there, too: https://www.youtube.com/watch?v=H2fmt3vLjvA

[janvangastel]

Thank you Bruce. Interesting feature, these lithosomes and again an interesting article.