Choanocystis kareliensis Mikrjukov, 1994
Diagnosis: Cells are 20–23 µm in diameter with plate-scales and one type of spicules in the periplast. Spicules are straight, 6.0–7.6 µm long (rare are curved from the heart-like base-plate, which is 1.2–1.35µm in diameter), the shaft is cylindrical, 0.3 µm in diameter, with a pointed apex. Plate-scales are dumb-bell-shape, 3.3–3.7 µm long, with a strongly developed medial constriction, 0.6–0.7 µm wide, surrounded by a thin marginal rim, carry numerous fine papillae in the central area.
Ecology: Marine. White Sea.