In trying to isolate Trebouxia from an Evernia lichen. I found that some of the cultures are contaminated by a what I think are rotifers. I am not sure of what kind of rotifer (or other organism) is the one pictured, so if anyone has some idea please let me know.
I also recorded a video of what I think are belloid rotifers feeding on the same lichen culture:
https://peertube.uno/w/uoSCNagVVmbuMcgXdVfPGR
I don't have much hope that the algae will survive this attack, but I might turn those jars into rotifer cultures.
I wonder if UV illumination of the lichen would work to preferentially eliminate tiny animals. I think the algae is rather resistant when it is in the lichenized body.
Currently I am breaking up lichen into small pieces and placing the pieces into jars with sterilized water that contains some nutrients (ammonium sulfate, (di)ammonium phosphate, potassium sulfate). I place the jars through my apartment under different light conditions.
The idea is to preferentially grow algae by having low phosphate and exposing to the sun, dilute, grow again, dilute, and repeat a few times to purify. Similar to how I purify a wild mushroom through agar transfers. In the past I did succeed growing a bunch of Trebouxia but I left those jars standing for two years and now they have a wild mixture, so I am starting the process again.