Strombidium apolatum, Wilbert & Song, 2005

Wilbert, Norbert & Song, Weibo, 2005, New contributions to the marine benthic ciliates from the Antarctic area, including description of seven new species (Protozoa, Ciliophora), Journal of Natural History 39 (13), pp. 935-973 : 953-955

publication ID 10.1080/00222930400001509

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scientific name

Strombidium apolatum

sp. nov.

Strombidium apolatum nov. spec.

( Figures 8 View Figure 8 , 14A–I View Figure 14 ; Table VI)


Cordiform Strombidium in vivo about 50640 M m; ca 13 collar and seven buccal membranelles not continuous; girdle and ventral kinety with ca 45 and 60 basal body pairs, respectively; single elongate to sausage-like macronucleus; extrusomes evenly distributed along the somatic kineties; marine habitat.


Composite of apo (derived from) and the species name latum , indicating that this species is different from the congener S. latum .


Size about 40–60630–45 M m in vivo, after fixation ca 35–50 M m in length; cell ratios about 3:2 for length/width and ca 4:3 for dorsoventral flattening. Body shape consistently cordiform, often slightly asymmetrical when viewed ventrally; anteriorly broadly rounded, posteriorly slightly pointed ( Figure 8A View Figure 8 ). Buccal cavity shallow, about one-quarter of cell length. Transparent subpellicular platelet layer in posterior three-quarters of cell ( Figure 8G View Figure 8 , arrow), although the polygonal platelets often found in other congeners were not detected here. Equatorial girdle in anterior two-thirds length, ca 2 M m wide, immediately ahead of subpellicular platelet layer ( Figure 8H View Figure 8 , arrow); extrusomes densely and uniformly distributed, inserting along girdle ( Figure 8D View Figure 8 , arrows).

Cytoplasm tightly packed with dark globules (especially directly below the cell surface) and lipid droplets, rendering cells dark to almost black at low magnification. Macronucleus elongated to sausage-like (but sometimes irregularly shaped after fixation), about 25– 3067–10 M m in size, with many large nucleoli ( Figures 8H View Figure 8 , 14D, H View Figure 14 ). Micronucleus not detected.

Movement fast and almost without pause, hectically to and fro on the debris ( Figure 8C View Figure 8 ).

Adoral zone spirally around peristomial field, cilia of most membranelles about 25– 30 M m long, always extending anteriorly ( Figure 8A View Figure 8 ). Twelve to fourteen collar membranelles (CM), bases ca 7 M m in length and conspicuously longer than those in buccal zone. The buccal zone (BM) consists of six to eight membranelles and is positioned in the shallow buccal cavity, hence conspicuously separated from the CM ( Figure 8F View Figure 8 ). Pharyngeal fibres highly developed, ca 20 M m long and extending obliquely to right side ( Figure 8F, G View Figure 8 ).

Girdle kinety (equatorial kinety) composed of about 45 dikinetids (n 55), running along the edge of subpellicular platelet layer, begins at right margin, turns to dorsal side and then curves slightly towards the posterior (but clearly separated from the ventral kinety; Figure 8H View Figure 8 , arrowhead). Ventral kinety more densely ciliated than girdle one, containing ca 60 basal body pairs, extending from right body margin subcaudally to the left and terminating laterally at posterior end of girdle kinety at level of about anterior third of cell length ( Figure 8H View Figure 8 ). Cilia in girdle kinety about 2 M m long, while in ventral one ca 5 M m in length ( Figure 8G, H View Figure 8 ).


The genus Strombidium is a species-rich taxon containing more than 30 nominal species ( Kahl 1932; Maeda and Carey 1985; Lynn et al. 1988; Montagnes et al. 1988, 1990; Montagnes and Taylor 1994; Montagnes and Lynn 1991; Lynn and Gilron 1993; Petz et al. 1995). With respect to the subpellicular platelet layer which covers almost two-thirds of cell length, the flattened body shape, the shallow buccal cavity, densely arranged cilia in ventral kinety, the laterally positioned ventral kinety and the sausage-like macronucleus, this species clearly differs from all other known members of this genus ( Lynn et al. 1988; Montagnes et al. 1988, 1990; Montagnes and Lynn 1991; Petz et al. 1995; Song and Packroff 1997; Song et al. 2000).

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