A fungal hypha attacking and sticking Holophrya?

[NachoBen]

Hi everyone in the microworld!

Yesterday I stumbled upon another interesting phenomenon. In the attached video you can see an individual of Holophrya (perhaps H. teres) attached to the substrate by a filament. Holophrya apparently struggles to escape (or simply continue on its way) several times, until the filament breaks and the critter is free. However, part of the filament remains attached to the cell.



I don't know how to interpret this. I had never seen it. Years ago I observed what then seemed to me to be Ophryoglena in a similar situation, although the "filament" was more elastic and looked almost like a cytoplasmic bridge.

It occurs to me that it could be a fungal hypha, although it could also be something more mundane: a fiber ingested and then excreted by Holophrya, only to be stuck to the substrate and to retain the cell.

Anyway, any help will be welcome!

[Bruce Taylor]

That holophryid is attempting to swallow the long filament. Being single-celled and not equipped with eyes it has no way of knowing that the object it is trying to consume is too big. It seems to have broken off a bit of it, but eventually gives up on trying to eat the rest.

Holophryids and Ophryoglena are both histophages (tissue-eaters) adapted for eating tasty pieces of dead things and chunks of loose organic matter.

[NachoBen]

Thank you, Bruce, in the right direction again!

Dr. Michael Plewka has kindly pointed me to a reference in the great work by Foissner, Berger & Kohmann: "Taxonomische und Ökologische Revision der Ciliaten des Saprobiensystems – Band III: Hymenostomata, Prostomatida, Nassulida." On page 338 it reads (translated from German): "Holophrya teres sometimes specializes in certain organic, shaped components
present in wastewater, e.g. on starch grains, on paper fibers or on drops of fat (KAHL 1930a, LIEBMANN 1962)."

So the supposed fungal fibers are actually cellulose fibers. In this new video you can clearly see two long fibers in the cytoplasm of Holophrya teres:



So one more problem solved!

[Bruce Taylor]

A lot has changed since 1994, when that (indispensable!) volume was published. Shortly before his death, Foissner published a complete nomenclatural revision of the holophryids, dividing Holophrya into four genera. These are distinguished by details of the brosse, which can sometimes be seen in the light microscope without special stains, with good magnification and careful microscopy. See: https://www.sciencedirect.com/science/a ... hBnBCiXuIg

[NachoBen]

Thank you very much for the reference and the link!