Probably Cyclidium genus
They are very small, about 20um long.
They have membranes in their "mouth" that sometimes fold them like bird wings
and a long caudal cilium
Phase contrast and oblique polarized light.
100X immersion objective
Panasonic GH4 camera with and without 2X zoom
Free network sound effects
Video link:
https://www.youtube.com/watch?v=WD3s3ovhe68
Video frame ONLY for preview:
Regards
carlos
