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

Intranstylum antarcticum nov. spec.

( Figures 5A–C , 13I–L )

Diagnosis

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.

Description

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 ). 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 ). 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 ). No differentiation of macro- and microzooids.

Remarks

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).

Figures

Figure 5. (A–C) Intranstylum antarcticum nov. spec. and (D–F) Telotrochidium sp. from life (A–C) and protargol impregnation (D–F). (A) Typical specimen, arrow marks the peristomelipe, double-arrowheads mark the reduced spasmoneme; (B) portion of stalk, arrow marks the myoneme, note the place where the myoneme is broken (arrowhead); double-arrowheads indicate the bacteria attached to the stalk; (C) to show the general stalk arrangement; (D) general view, to show the macronucleus (arrow) and infraciliature; (E) detailed part of aboral ciliary wreath; (F) buccal apparatus, arrow marks the peniculus 3, arrowhead indicates the haplokinety, doublearrowheads point to the epistomial membrane. Scale bars: 50 Mm (A); 200 Mm (C); 30 Mm (D).

Figure 13. Photomicrographs of (A–G) Pithites pelagicus nov. spec., (H, M) Pleuronema coronatum and (I–L) Intranstylum antarcticum nov. spec. after protargol impregnation. (A) Lateral view of the anterior portion; arrows mark the cytopharynx; (B) dorsal side view (looking from ventral to dorsal) of anterior portion, arrow indicates the terminal fragment (‘‘dorsal brush’’); (C) ventral view, arrows mark the gap between left and right somatic kineties; (D) ventral view, to show the contractile vacuole pore (arrow); (E) ventral view of apical area, arrows mark the fragment-like perioral kineties; (F) ventral view of a specimen in division; (G) ventral view at a later stage of division, white arrows mark the newly formed oral apparatus in the opisthe, while the black arrow indicates the contractile vacuole pore; (H) left-lateral view, the arrowheads point to the posterior end of paroral membrane, the black arrow indicates whereas the macronucleus; (I, L) stalk, arrowheads in (I) mark the attached diatoms (?); (J) two zooids, arrows indicate the reduced spasmoneme; (K) to show the spasmoneme (arrow); (M) left-lateral view, arrowhead marks the micronucleus, arrows point to the membranelle 3.