what is this ribbed, branched structure?

[apochronaut]

slow creek origin. i haven't come across this before, or haven't noticed. the ribs are very small, less than 1 um.

[actinophrys]

It looks a lot like the stalk from a colonial peritrich but with all the ciliates removed. Most pictures focus on the living cells and so don't show this level of detail for the stalks, but at least some Epistylis do show this same kind of fine pattern.

[apochronaut]

Thanks. I had assumed so but could not find any images that clearly showed such ridging on the stalk. Most, image the stalks as highly transparent.