is probably Thecamoeba striata
Measures about 120um in diameter.
I am grateful the continuing generosity and help of Ferry Siemensma:
http://www.arcella.nl/
Oblique polarized light.
40X objective.
Panasonic GH4 camera
Video link:
https://www.youtube.com/watch?v=Wg6OX5rMGXk
Video frame preview:

Regards
carlos