Lecythium hyalinum Hertwig & Lesser, 1874 emend. Dumack et al., 2016.
Diagnosis: Shell: round or spherical in shape. Nucleus: ellipsoid or spherical, about 11.5-21 µm in width. Nucleolus:one, rarely two adhering, round, 4-8 µm in diameter; central to nucleus. Aperture: roundish, vacuolated cytoplasm arises from the aperture. Cells show a clear zonation (apical to basal): (I) zone of nucleus (no granules or vacuoles), (II) zone of granules (III) zone of food vacuoles (IV) highly vacuolated cytoplasm in front of the aperture (contractile vacuoles) of which branching and anastomosing filopodia arise. Locomotion: (i) actively creeping, filopodia rarely extend longer than 70 µm; (ii) swimming with extended, non-branched and non-anastomosed and slowly moving filopodia. Filopodia with small granules attached to cytoskeletal filaments occur. Cell division: longitudinal, binary.
Dimensions: literature: 30-45 (Wailes); 18-50 µm (length), 24-61 µm (width), ratio 0.7-1 µm (Dumack et al. 2016; my measurements 27-44 µm.
Habitat: Prey: unicellular algae, no ingestion of bacteria observed. Very common and often abundant in different types of fresh water.
Remarks: This species is probably identical to Chlamydophrys stercorea. I have seen numerous specimens with the same anastomosing and spumose filopodia as described for C. stercorea. Distinction between Chlamydophrys and Lecythium is based on the presence of longitudinal division in Lecythium (Fresenius, Belar, 1921) and budding (Knospen) in Chlamydophrys (Belar, 1921).
