Unknown greenisch ciliate

[WWWW]

In a freshwater sample I found this green ciliate.
No idea what kind it is, size is 30x20 μm.

Can anyone help with the ID ?

Here the video:

[Bruce Taylor]

That's a really cute creature! It appears to be a scuticociliate, but with a somewhat Tetrahymena-like shape. It has a long caudal cilium, and a rather bumpy, ornamented pellicle. I'm thinking of Sathrophilus (=Saprophilus). The genus has not had much attention since Kahl, who described and illustrated a few species with a similar appearance: S. oviformis, S. ovatus, and S. chlorophaga. The last one is described as green (from ingested algae). However, that organism hasn't been described since Kahl (1931), and Kahl's illustrations don't seem to show a sculpted pellicle. However, pellicular "crenellations" are mentioned for certain marine species of Sathrophilus (Long et al.,Two New Ciliates from the North China Seas, 2007). Whether the Tetrahymena-like species in Kahl actually belong in Sathrophilus is uncertain, because they have not been redescribed.

Some Sathrophilus (Saprophilus) images from Kahl (S. chlorophaga is number 33):

Saprophilus from Kahl 2.jpg (29.51 KiB) Viewed 1244 times

[WWWW]

Thanks Bruce,

I noticed 4-5 long posterior cilia, mouth in the first half, CV at the posterior end. A almost central macronucleus. Couldn't see micronuclei.
I have no larger magnification nor other contrast methods, so this is the best result I could get with this little one.
Without extra information it will almost be impossible to get the right ID.

Again, thanks for the effort !

[Bruce Taylor]

Yes, good point....in addition to the caudal cilium there are several long posterior somatic cilia. That's not unusual for a scuticociliate, but it is an important feature. I see that Sathrophilus chlorophaga (number 33 in Kahl's plate, above) also has elongated posterior cilia.