Arcella sp.

Diagnosis: I observed one specimen with a neat oval aperture, but I could not observe it in lateral view. It might be an unknown species or an aberrant form. I do not think it is Arcella excavata.

Dimensions: Shell diameter 70 x 82 µm.

Ecology: Freshwater, meadow pond near Epen, Limburg, Netherlands, 2024.

A similar shell was found by Harry Mueller, Canada, 2025. He wrote: “The size of the specimen is 78 µm X 62 µm and the aperture is 41 µm X 22 µm.
The location on Google Earth is 49°42’53″N 96°27’25″W, about 4 miles north of Richer, Manitoba. It’s a plant choked ditch connected to marshy area. The main species of testate amoebae in my samples at this location is Cucurbitella vlasinensis while the main ciliate species are from the Loxodes genus, the latter being indicative of low-oxygen environments.