Euplotes rariseta Curds et al., 1974

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 : 1002

Euplotes rariseta Curds et al., 1974

( Figures 13I–N ; Table 4)

This extremely small organism was redefined by Song and Packroff (1997) based on a Chinese population. The Antarctic sample corresponds quite well to that redescription.

Description

25–40 Mm in vivo, but mostly about 30 Mm long after protargol impregnation, consistently oval in shape with relatively long cilia in all ciliary organelles. Buccal field about two-thirds of body length; adoral zone evenly curverd with about 20 adoral membranelles ( Figures 13I, M ). All cirri comparatively weak, 10 frontoventral, five densely arranged transverse and two caudal cirri; invariably (and uniquely) one marginal cirrus ( Figures 13I, M , arrows). Dorsolaterally mostly seven (7–8) kineties, of which the mid-rows have approximally only 6–7 dikinetids, hence are loosely ciliated ( Figure 13J ). Macronucleus quite variably shaped.

Remarks

This organism differs from the similar congener Euplotes balteatus in its smaller size ( Table 4), relatively weaker cirri, lower number of membranelles (17–21 versus 27– 33), consistently single marginal cirrus (versus two in the latter) and different pattern of silverline system on dorsal side (double- patella type versus double- eurystomus type) ( Song and Packroff, 1997; Song and Wilbert, 2002a). In addition, unlike E. balteatus , the five transverse cirri in E. rariseta are not only comparatively less strong but also conspicuously closely spaced ( Figures 13K–M versus A). The morphotype described in 1995 by Petz, Song and Wilbert under the name of E. rariseta should be regarded as a misidentification, and is now believed to be a Euplotes petzi (see above). The two forms can be separated at both morphological and morphometric levels ( Table 4).

Euplotes vannus (Mueller, 1786)

( Figures 3B, C , 10F )

Only a few specimens were found from the protargol-impregnated slides. All morphological features correspond perfectly to the populations found from other geographic sites ( Figures 3B, C ): the size (c. 80–100 Mm), the ciliature pattern, the sharply bending, hook-like posterior part of adoral zone, the characteristic three caudal cirri and the number of dorsal kineties (10–11) (see also Song and Packroff 1997).

As far as the authors know, this is the first time this species has been identified from the Antarctic region.

Figures

Figure 3. Pseudocohnilembus persalinus (A), Euplotes vannus (B, C), Metaurostylopsis marina (D, E) and Holosticha apodiademata nov. spec. (F, G) after silver-nitrate (A) and protargol impregnation (B–G). (A) Ventral view of silverline system, arrow marks the small membranelle 3. (B, C) Ventral and dorsal view of the same specimen, arrow in B indicates the paroral membrane. (D, E) Ventral and dorsal views of the same specimen, doublearrowheads mark the posterior end of the ventral row, which is continued by the short midventral rows, while the arrow indicates the buccal cirrus. (F, G) Ventral and dorsal view of the same specimen, arrow marks the big gap between the two parts of the adoral zone. AZM, adoral zone of membranelles; CC, caudal cilia (in A) or caudal cirri (in B); BC, buccal cirrus; Cs, cytostome; CVP, contractile vacuole pore; CyP, cytopyge; DK, dorsal kineties; FC, frontal cirri; FTC, frontoterminal cirri; FVC, frontoventral cirri; M1, M2, membranelles 1 and 2; Ma, macronucleus; MC, marginal cirri; MVR, midventral rows; PM, paroral membrane; SKn, last somatic kinety; TC, transverse cirri. Scale bars: 25 Mm (A); 40 Mm (B–E); 50 Mm (F, G).

Figure 10. Condylostoma spatiosum (A, B), Diophrys scutum (D), Diophrys aff. oligothrix (C, G), Diophrys appendiculata (E), Euplotes vannus (F) and Euplotes dragescoi nov. spec. (H–K) after protargol impregnation. (A) Dorsal view, to show the general appearance, arrow marks the beaded macronucleus. (B) Caudal portion, arrowhead marks the suture. (C) Dorsal view, to show the dorsal kineties (arrows). (D) Ventral view, to show the general infraciliature. (E) Ventral view, arrow marks the pre-transverse cirrus, double-arrowheads indicate the transverse cirri, while arrowhead points to the anterior marginal cirrus. (F) Dorsal view, arrowheads mark the three caudal cirri, arrow indicates the macronucleus. (G) Ventral view, arrow marks the pre-transverse cirrus. (H) Detail of a divider, arrowheads mark the newlyformed two marginal cirri (note the different sizes). (I) Dorsal view, to show the ridges. (J) Ventral view, arrow marks the anterior (large) marginal cirrus, double-arrowheads indicate the paroral membrane. (K) Detail of ventral view, arrow and arrowhead indicate the small and large marginal cirrus, respectively. Scale bars: 200 Mm (A); 100 Mm (D); 50 Mm (E–G, J).

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).