Choanocystis ebelii (Wujek et Elsner, 1992) Mikrjukov, 1997
Diagnosis: Periplast is 20–45 µm in diameter with plate-scales and one type of spicules. Spicules are 9.7–14.1 µm long; the shaft is hollow, 0.3–0.6 µm thick at the base and tapers up to 0.2–0.35 µm below an acute apex; the shaft originates from the heart-like base-plate, 2.4–5.6 µm in diameter; the base-plate is surrounded by a marginal rim and is ornamented with 25–60 radial ribs about 0.05 µm wide, which can sometimes branch; small papillae, up to eight, are irregularly located on ribs. Plate-scales are curved, 7.2–8.5 x 1.5–1.8 µm, their medial part is strongly thickened and is ornamented with subparallel ribs.
Ecology: Freshwater, occasionally marine. India (Wujek & Elsner, 1992), marine ice in Antarctica (as Acanthocystis sp., Takahashi, 1981).