Family: Body ellipsoidal, uniformly ciliated; hypostomial frange short; prominent cytopharyngeal apparatus (Carey, 1992). Genus: Oral aperture small, oval (Carey, 1992). Species: Cell body ovoid and small in size, less than 100 μm long; cytopharyngeal basket large, 60 μm long; macronucleus spherical; a single contractile vacuole in the mid-body region; trichocysts absent (Carey, 1992).

Similar species --> Paranassula

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640

Nassula sp. (small type), conjugating pairs, x 400, x 640, Higashi-hiroshima, Hiroshima Pref., Japan, October 1998, by Y. Tsukii

Nassula parva Kahl, 1928: Small, ovoid with large cytopharyngeal basket; 60 μm long; a spherical macronucleus; single contractile vacuole in mid-body region; details of range and suture not given (Carey, 1992).

Nassula rubens Perty, 1852: Small, ellipsoidal; 50-70 μm long; long cytopharyngeal basket; single contractile vacuole; single macronucleus; many trichocysts (Carey, 1992).

Nassula citrea Kahl, 1931: Ovoid or ellipsoidal, anterior not expanded; 70-90 μm long; frange equipped with long membranelles; cytopharyngeal appratus unremarkable; single contractile vacuole; single ovoid macronucelus (Carey, 1992).