Hedriocystis minor Siemensma, 1991

Diagnosis: Shell spherical or ovoid, smooth, tapering towards the stalk; some small pores; shell hyaline, colorless or faint yellow; cell body doesn’t fill the shell completely; nucleus subcentrally; one contractile vacuole; axopodia not numerous, fine; no swarmer observed.

Dimensions: shell 8-13 µm, stalk up to 30 µm long.

Habitat: fresh water, on submerged aquatic plants, Sphagnum; the Netherlands, Austria.

Remarks: rare, but easily overlooked, because of its small size.