Intranstylum antarcticum, 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 : 948-949

publication ID 10.1080/00222930400001509

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scientific name

Intranstylum antarcticum

sp. nov.

Intranstylum antarcticum nov. spec.

( Figures 5A–C View Figure 5 , 13I–L View Figure 13 )


Large-sized marine Intranstylum ca 100660 M m in vivo with ellipsoidal body shape, smooth pellicle and thick, single-layered peristomial border; one contractile vacuole located apically; macronucleus C-shaped, transversely positioned. Colony large, with about 20 or more zooids; stalk smooth, with regular, dichotomous branching; myoneme long with branches of different thickness.


Zooids in similar size, in vivo about 100 M m long with thick, single-layered peristomial border; body form-constant, slender and elongated vase-shaped, only slightly constricted below peristomial collar; peristomial disc large and flattened ( Figure 5A View Figure 5 ). Cells not very sensitive to mechanical stimuli. When contracted, zooids usually globular in shape with distinctly truncated or folded plate at both cell ends. Pellicle smooth when observed at low magnification, fine transverse striations recognizable only under high magnification, with no visible granules or any other pellicular structure. Cytoplasm colourless or slightly greenish, usually containing many food vacuoles, which are oval or irregularly shaped and measure about 3–6 M m in length ( Figure 5A View Figure 5 ). Contractile vacuole large, apically located. Macronucleus C-shaped, thick and transversely positioned.

Colony large (probably over 500 M m in length), having about 20 (probably more?) zooids and a regular dichotomously branching stalk. Stalk with smooth surface, about 10 M m thick. Myoneme system consisting of long spasmoneme within stalk, which is about as long as the body length, relatively poorly developed as described in previous report (Song and Wilbert 2002 under the name of Zoothamnium sp.). In the present population, spasmoneme also varied in length (20–100 M m) and in different parts of the stalk thickness ( Figure 5B View Figure 5 ). No differentiation of macro- and microzooids.


Though numerous cells/colonies were found, no information about the infraciliature is available due to over-staining of the impregnation. Hence the comparison to known congeners can be carried out only on the basis of observations in vivo.

This new species can be recognized by the combination of the following characters: large cell size and dichotomous by branched stalk, long and poorly developed spasmoneme, generally oval to ellipsoidal body shape of zooids and the marine habitat ( Kahl 1935; Stiller 1971; Song et al. 2003).

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