Chilodonella unicinata

[janvangastel]

I found this small ciliate (about 45 microns long) in a ditch nearby. I think it is C. unicinata, but I am not 100% sure.

[Bruce Taylor]

Cute little guy. A chlamydodontid for sure, and probably a chilodonellid. Chilodonella is certainly one of the suspects, but cell shape and the existence of a cyrtos are not really enough for a reliable genus ID...you'd want to see details that are missing here (ventral ciliation, shape of suture, dorsal brush, complete cyrtos, etc.)

[janvangastel]

Thanks Bruce. Very difficult to make small details visible on such small creatures, alas. At least with my equipment and knowledge. I was already satisfied when I found a candidate with the two CV's in the right place, but that's not enough of course.

[janvangastel]

I made a new video, now with higher magnification. There's not much more information in it compared to the orginal video, but the cirri at the front side and the mouth region are a little better visible.

[Bruce Taylor]

Oh, that's much clearer. We see right away that the ventral surface is largely unciliated in the central area. That rules out some common cyrtophorians, such as Trithigmostoma. We see an unbroken preoral suture (that little "horizontal" line just forward of the mouth opening), so we can rule out Pseudochilodonopsis.

Overall, it looks very much like Chilodonella uncinata, as you noted earlier. However, it happens that there is a second chilodonellid species that can add some confusion! In 1st vol. of their "ciliate atlas" (1991), Foissner et al. note that the species Odontochlamys alpestris is very similar to C. uncinata but differs in having its "dorsal brush" (a tuft of projecting cilia) at the very anterior of the cell. I think we see this structure at several points in the video, a tuft of unmoving cilia projecting from the apical surface of the cell (0:29, 0:53, etc.) The outline of the dorsal surface (unless I am reading it wrongly) also seems consistent with that species.

So, I would say it's certainly a chilodonellid, and possibly (likely?) Odontochlamys alpestris.

If you have a chance to observe these again, look for a curious characteristic of that species. Apparently, these things encyst very rapidly, and can frequently be seen doing so while under the microscope slide! So, if you still have the water sample it might be worth trying to witness this transition.

[janvangastel]

Thank you Bruce.
Yesterday I aslo arrived at Odontochlamis alpestris, but I couldn't decide. I only saw it in Foissners key and not in the other one I use. In Kahl I found the name only once, as synonymous for Chilodonella.

[KD Arvidsson]

Another nice work Jan //KD

[janvangastel]

Thank you KD. It's really fascinating, those one cell creatures. Small, but very complete. I always wonder if some species are 'social' in any way. They can get together of course because of specific circumstances, such as food, water temperature, hiding places, but maybe there's also something social. But maybe that's nonsence, I don't know.