Euplotes petzi, Wilbert & Song, 2008

Wilbert, Norbert & Song, Weibo, 2008, A further study on littoral ciliates (Protozoa, Ciliophora) near King George Island, Antarctica, with description of a new genus and seven new species, Journal of Natural History 42 (13 - 14), pp. 979-1012 : 999-1002

Euplotes petzi nov. spec.

( Figures 6A–G , 13E–H ; Tables 4 and 5)

Diagnosis

Small marine Euplotes with conspicuous dorsal ridges, 50–80×30–50 Mm in vivo; buccal area about 2/3 of cell length with about 30 membranelles; always 10 frontoventral, five transversal, two caudal and two closely spaced, extremely fine marginal cirri; six dorsal kineties with about eight dikinetids in mid-dorsal rows. Macronucleus curved bar- or C-shaped. Found in Antarctic area.

Type locality

In benthos samples from rockpools and the littoral zone on the sea coast near Bellinghausen Station, King George Island (62 ° 139S, 58 ° 589W).

Dedication

We dedicate this species to our colleague, Dr. Wolfgang Petz, Zoologisches Institut der Universität Salzburg, Austria, in recognition of his great contributions to the studies on ciliates in Antarctica as well as his excellent descriptions of this organism as senior author ( Petz et al. 1995).

Description

Body shape generally elongate oval as shown in Figure 6A . In vivo usually 60–70 Mm long; about five dorsal ridges conspicuous ( Figure 6C , arrows). Buccal field prominent, adoral zone evenly curved. Most other features of living morphology, including movement, similar to the 1995 population (see Petz et al. 1995). Macronucleus variable in shape: from slightly curved (mostly) to typical C-shaped ( Figures 6B, F, G ). Ciliary pattern rather consistent ( Figure 6E ), always 10 frontoventral (FVC) and five strong transversal cirri (TC). Left marginal cirri (MC, Figure 6E ) uniquely positioned: invariably two in number, fine and close together (could be regarded as a single following overstained silver-nitrate impregnation) with cilia about only 10 Mm long. Dorsal rows along ridges, conspicuously loosely ciliated ( Figures 6F, G , 13F ).

Silverline system not revealed in current isolation, though the 1995 population was reported as ‘‘double- patella type’’ ( Petz et al. 1995), i.e. similar to that of E. rariseta . But a re-check and re-investigation of this critical character are necessary.

Remarks

This new species was/is found, to date, only in the Antarctic area ( Agatha et al. 1993; Petz et al. 1995; present work) and hence is possibly a real Antarctic ‘‘local form’’. It differs from the morphologically closely- related congener, E. rariseta , in having 2 close-set marginal cirri (versus 1), larger size, stronger cirri and more membranelles ( Table 4). It can be separated from E. balteatus regarding the appearance of adoral zone (evenly curved versus sharply bending at posterior portion), conspicuously lower number of dorsolateral kineties (see Table 4), as well as the structure/arrangement of the marginal cirri (fine and closely spaced versus strong and far away from each other). In addition, the latter form is mostly broadly oval (versus slender oval) and smaller (mostly about 50 Mm versus mostly 60–70 Mm).

Agatha et al. (1993) reported an Euplotes sp. from the same area according to the information they have given; it could be conspecific with our new species though some statistical data are slightly different.

Comparison with other small, equally Antarctic-inhabiting forms is documented in Table 4; the new species described here can be clearly recognized by the combination of either the ciliature pattern/appearance of ciliary organelles or by other morphometrical and statistical data ( Agatha et al. 1990, 1993).

Figures

Figure 6. Euplotes petzi nov. spec. from life (A, C, D) and after protargol impregnation (B, E–G) (C, D, G; after Petz, Song and Wilbert 1995). (A, D) Specimens found in 2006 population (A) and 1995 population (D), note the different lengths of most ciliary organelles. (B) Different shapes of macronucleus. (C) To show the dorsal ridges (arrows). (E, F) Ventral and dorsal view of a specimen from 2006 population. (G) Dorsal view of a specimen from the population studied by Petz et al. 1995. CC, caudal cirri; DK, dorsal kineties; FVC, frontoventral cirri; Ma, macronucleus; MC, marginal cirrus; Mi, micronucleus; TC, transverse cirri. Scale bars: 30 Mm.

Figure 13. Euplotes balteatus (A–D), Euplotes petzi nov. spec. (E–H) and Euplotes rariseta (I– N) after protargol impregnation. (A–C) Ventral view of three specimens, to show the general appearance of infraciliature, arrow in A marks the strong and loosely arranged transverse cirri, arrowheads in C indicate the two marginal cirri. (D) Dorsal view, note that the basal bodies are loosely arranged. (E, G, H) Ventral view, note the two small and closely- spaced marginal cirri (arrow and arrowheads). (F) Dorsal view. (I, K) Ventral view, arrows mark the single marginal cirrus, arrowheads in K indicate the weak and close-set transverse cirri. (L) Ventral view, arrowhead marks the two anteriormost frontoventral cirri. (M) Ventral view, to show the adoral zone and the marginal cirrus (arrowhead). (N) Ventral view, arrow indicates the paroral membrane. Scale bars: 20 Mm (A, I); 35 Mm (E).