Meunier (1910: 154, pl. 15, figs 9–15)
Petz et al. (1995: 21)
In vivo 70–200 × 50–120 µm. Body barrel-shaped to globular, with anterior oral cone (proboscis). Somatic kineties 50–75, longitudinal, non-ciliferous except for 2 ciliary bands (1 at anterior end of kineties and 1 in posterior quarter of body). Brosse posterior to each ciliary band (wreath), composed of 2 or 3 short rows. Extrusomes of 3 types: rod-like cyrtocysts; fusiform pexicysts (4–6 µm long); and toxicysts 40–50 µm long, between nematodesmata. Macronucleus sausage-shaped. Contractile vacuole probably terminal. Movement: moderately fast.
Pacific sector of the Southern Ocean (Mamaeva, 1984, 1986); Ross Sea, in the region 68.98°–76.60°S and 134.98°–165.47°W, in sea-ice and occasionally in the plankton (Petz, unpublished data); Atlantic sector of the Southern Ocean (Mamaeva, 1989); Weddell Sea (Garrison & Buck, 1989a; Petz et al., 1995); Barents Sea (Meunier, 1910); Baltic Sea (Biernacka, 1963); Pacific (Hada, 1961).
The freshwater species Didinium nasutum (?), reported by Schröder (1906a) without further description from the Indian sector of the Southern Ocean, is considered to be conspecific with D. gargantua.