Ciliate or Turbellarian?

[NachoBen]

I have come across this organism in a freshwater sample full of Rotifers, Gastrotrichs, Amoebae (Polychaos, Difflugia, Cylindrifflugia, Netzelia), Ciliates (Ophryoglena, Stentor, Holophrya, Lacrymaria), Turbellarians (Stenostomum) and this little enigma.

Original footage video:




Trimmed version:



It looks like a hybrid of a Ciliate and a Turbellarian worm, if such a thing were possible!

I'm not at all sure what it could be as it shows equivocal characteristics. It could be an immature form of the Stenostomum unicolor turbellarian or a ciliate I can't identify.

Thanks so much for any help!

[sreynolds]

Your images are very good. Can you describe the setup you are using for the live specimens - scope, objectives, illumination, camera, wet-mount prep? Thanks.

[macnmotion]

Just ball parking, I've had somewhat similar plump organisms with a small proboscis identified as Trachelius. My first one had the proboscis almost not visible because the organism was confined by the cover slip. Later ones showed a more visible proboscis. I see what might be a small proboscis on yours. But there are members here that could probably tell in a second if Trachelius was not possible based on other aspects.

[NachoBen]

Your images are very good. Can you describe the setup you are using for the live specimens - scope, objectives, illumination, camera, wet-mount prep? Thanks.

Thank you, Steve. Here you are:

Microscope: OMAX - M837ZL-C180U3
https://www.amazon.co.uk/OMAX-40X-2500X ... C98&sr=8-1

Illumination: Bright field, sometimes with Rheinberg filters.

Objectives: 4x, 10x and 40x from the pack, and 60x dry objective (AmScope A60).

Eyepiece: 10x from the pack, inserted into the photographic tube.

Smartphone to eyepiece adapter:
https://www.amazon.es/dp/B07QLB16Y9?ref ... b_ap_share

Smartphone: Xiaomi Redmi Note9, using the 5 Mpx macro lens and the Open Camera app.

Videos processed with InShot app on the smartphone and with VSDC software on the PC.

[NachoBen]

It seems Trachelius may be a good clue to follow, thank you.

Just ball parking, I've had somewhat similar plump organisms with a small proboscis identified as Trachelius. My first one had the proboscis almost not visible because the organism was confined by the cover slip. Later ones showed a more visible proboscis. I see what might be a small proboscis on yours. But there are members here that could probably tell in a second if Trachelius was not possible based on other aspects.

[Bruce Taylor]

I can see why macnmotion is thinking of Trachelius, but the membranous structure that surrounds this critter is too thick to be the cortex of a tracheliid, or any ciliate...I'm pretty sure it's the ectoderm of some kind of flatworm, or perhaps a freshwater acoel. It encloses structures that appear to be organs, rather than organelles, and we don't see the things I would expect to find in the cytoplasm of a ciliate. The movements are distinctly flatwormish, as well...the occasional pinching or squeezing of the body, followed by slight elongations. This thing has muscles of some kind.

[macnmotion]

I can see why macnmotion is thinking of Trachelius, but the membranous structure that surrounds this critter is too thick to be the cortex of a tracheliid, or any ciliate...I'm pretty sure it's the ectoderm of some kind of flatworm. It encloses structures that appear to be organs, rather than organelles, and we don't see the things I would expect to find in the cytoplasm of a ciliate. The movements are distinctly flatwormish, as well...the occasional pinching or squeezing of the body, followed by forward jerks (in the first few seconds of the first video, for instance). This thing has muscles of some kind.

Bruce, I was hoping you would see my reply -- and correct it!

[Bruce Taylor]

It's oddly shapeless, for a flatworm. I don't know much about them, unfortunately. It crossed my mind that it might be a freshwater acoel, but I really have no idea.

[NachoBen]

Thank you everybody for your help.

After reading Bruce's post, I think now It could be a miracidium larva of a flatworm searching for a host (perhaps a freshwater snail) to parasitize.