Choanocystis minima Zlatogursky, 2010
Diagnosis: Cell body ca. 3 µm in diameter; including basal parts of scales – about 5 µm. Axopodia ca. 17 µm long. Plate scales are oviform. Length of plate scales is1.5-2.0 µm, while width is about 1.2-1.3 µm. Radial scales are with heart-shaped base. Cylindrical radial scale shaft is truncated on the tip. Length of radial scales is 2.0-5.0 µm, thickness is 0.1-0.2 µm. Cells are tightly adhered to the substratum.
Differential diagnosis: Choanocystis minima has radial scales with truncated tips and without teeth. Choanocystis lepidula and C. rossica also have radial scales of this type. However, the base of the radial scale in C. lepidula is surrounded by a hollow rim, and plate scales of this species have a longitudinal rib. Choanocystis minima lacks both these features. Choanocystis rossica has radial scales with a shaft widened toward the base and plate scales with well-developed lateral notches. In contrast, radial scales in Choanocystis minima are of a homogenous thickness, and plate scales of this species lack the notches. In addition, this heliozoan is smaller than all other species so far described.
Ecology: Leshovoe lake, Valamo island, North-Western Russia.