D. anser (Müller, 1786) Dujardin, 1840: 
250-400 (sometimes up to 600) μm long; 
numerous macronuclei; contractile vacuoles in a row on the aboral surface (Kudo, 1966). 
200-600 μm long; small tail region; 
200-500 very small macronuclei; contractile vacuoles from anterior to posterior on the dorsal surface 
(Carey, 1992).  
D.  aculeatus Dragesco, 1960:  Elongate; 
300 μm long; long sharply pointed tail; 
4 large rectangular macronuclei; a row of contractile vacuoles on dorsal surface 
(Carey, 1992).