Elongated ciliate

[Wes]

Any idea what species this is?

[janvangastel]

Looks like Spirostomum. But I don't know which species.

[Wes]

Thanks Jan, I was thinking about one of the following: Grubberia, Anigsteinia, Geleia and Tracheloraphis.


edit: I think you got it right, it has features very reminiscent of Spirostomum

[Bruce Taylor]

It's clearly a heterotrich, so definitely not Geleia or Tracheloraphis. Freshwater or salt? Anigsteinia & Gruberia are marine genera. If this was found in freshwater, my first suspicion would be Pseudoblepharisma. If it's a Spirostomum, it's not a mature specimen (body proportions are wrong, and posterior vesicle is too large).

[Wes]

It's clearly a heterotrich, so definitely not Geleia or Tracheloraphis. Freshwater or salt? Anigsteinia & Gruberia are marine genera. If this was found in freshwater, my first suspicion would be Pseudoblepharisma. If it's a Spirostomum, it's not a mature specimen (body proportions are wrong, and posterior vesicle is too large).

Amazing, thanks a lot Bruce, your ID skills are awesome. While not seen in the video the organism could contract along its body length (and yes its from fresh water).

[Bruce Taylor]

Aha, another clue! If it contracted quickly and dramatically in response to sudden movements, then we can probably rule out Pseudoblepharisma. That genus is not particularly contractile, which throws suspicion back upon Spirostomum. It might be a Spirostomum that has recently divided, and not yet regained its full length. Here, for interest's sake, is a species of Pseudoblepharisma: https://www.youtube.com/watch?v=YpDhkZMLBO8

[Wes]

Aha, another clue! If it contracted quickly and dramatically in response to sudden movements, then we can probably rule out Pseudoblepharisma. That genus is not particularly contractile, which throws suspicion back upon Spirostomum. It might be a Spirostomum that has recently divided, and not yet regained its full length. Here, for interest's sake, is a species of Pseudoblepharisma: https://www.youtube.com/watch?v=YpDhkZMLBO8

I had your video open in another tab

Well it contracted but not particularly fast or often and it didn't care if I tap the slide. Also it doesn't have the beads-on-a-string nucleus of Spirostomum

I threw a bit of food into the sample and these guys multiplied overnight which gave me a chance to take another video.

So Pseudoblepharisma?

[Bruce Taylor]

Spirostomum teres.

[Wes]

Spirostomum teres.

Now that's a match! Thanks!

[Wes]

A close-up

[Bruce Taylor]

That guy really plumps up when he's squashed.