Sterkiella tetracirrata Kumar et al., 2015

Min, Kyu-Seok Chae and Gi-Sik, 2022, New record of three oxytrichid ciliates (Ciliophora: Oxytrichidae) from South Korea, Journal of Species Research 11 (4), pp. 287-295 : 293-294

3. Sterkiella tetracirrata Kumar et al., 2015 ( Table 1,

Figs. 6 and 7 )

Sterkiella tetracirrata Kumar et al., 2015: p. 86 .

Korean name. IJūAEŀljǿAEệ

Material examined. Soil , Cheonan-si, Chungcheongnam-do, South Korea (36°54 ʹ 03.9 ʺ N 127°12 ʹ 21.1 ʺ E, 1), collected by Kyu-Seok Chae in June 2019 .

Diagnosis of the Korean population. Size in vivo about 110 × 55 μm, ellipsoidal body shape; 4 macronuclear nodules; contractile vacuole at left of mid-body; 25-40 adoral membranelles; cortical granules absent; 3 frontal cirri; 4 frontoventral cirri; 3 postoral ventral cirri; 2 pretransverse cirri; 4 transverse cirri; one buccal cirrus; one left and one right marginal cirral row; 3 caudal cirri; 4 dorsal and 2 dorsomarginal kineties.

Description. Body size in vivo 100-120 × 50-60 μm, 85-122 × 40-67 μm after protargol impregnation ( Table 1). Body shape elongated elliptical with rigid cortex ( Figs. 6A , 7C, 7E, 7F ). Length to width ratio about 2:1. Contractile vacuole on left side of mid-body, about 14 μm in diameter ( Figs. 6A , 7B , arrow). Four macronuclear nodules and three to six micronuclei ( Figs. 6C , 7D ). Cortical granules absent. Cytoplasm colorless.

Adoral zone membranelles conspicuous, about 32% of the body length, comprising 25-40 membranelles ( Fig. 6B , Table 1). Both paroral and endoral membranes curved leftward anteriorly ( Fig. 6B ). Three frontal, one buccal, three postoral-ventral cirri, two pretransverse and four transverse cirri ( Figs. 6B , 7E , Table 1). One right (24-30 cirri) and left (21-30 cirri) marginal row ( Figs. 6B , 7E , Table 1). Dorsal ciliature composed of four kineties and two dorsomarginal rows, three caudal cirri located at ends of dorsal kineties 1, 2, 4 on posterior end ( Figs. 6C , 7F , Table 1).

Distribution. India and South Korea (This study).

Remarks. Sterkiella tetracirrata differs from S. cavicola (Kahl, 1935) Foissner et al., 1991 by the number of transverse cirri (4 vs. 5) ( Foissner et al., 1991). Sterkiella tetracirrata can be distinguished from S. quadrinucleatus (Sick, 1933) Berger, 1999 by the number of transverse cirri (4 vs. 6-8) and habitat (soil vs. marine or brackish) ( Berger, 1999). Sterkiella tetracirrata differs from S. terricola Berger, 1999 in the number of adoral membranelles (25-40 vs. 22-23), transverse cirri (4 vs. 3), and right and left marginal cirri (about 26 and 24 vs about 20 and 17) ( Berger, 1999).

The morphology of the Korean population corresponds to the type population from India, but they are slightly different in the number of right and left marginal cirri (24-30 and 21-30 vs 21-25 and 20-23) ( Kumar et al., 2015) .

The 18S rDNA gene sequence of S. tetracirrata was 1770 bp in length (GenBank accession number: OM 212986). The Korean and Indian populations formed a highly supported clade (99% ML, 0.94 BI) in the phylogenetic tree (double-arrowhead in Fig. 8 ). The Korean and the Indian populations were identical, and had a sequence divergence of 0.12% to its congener S. multicirrata (2 nt difference).

Deposition. The voucher slide with protargol-impregnated specimens is deposited in the National Institute of Biological Resources in Korea (NIBRPR0000110852).

Figures

Fig. 6. Morphology of Sterkiella tetracirrata from live (A) and protargol-impregnated (B, C) specimens. A, Ventral view of typical speci- men; B, C, Ventral and dorsal view of typical specimen; AZM, adoral zone of membranelles; BC, buccal cirri; CC, caudal cirri; DM, dorso- marginal row; E, endoral membrane; FC, frontal cirri; LMR, left marginal cirral row; PTC, pretransverse cirri; RMR, right marginal cirral row; TC, transverse cirri; 1-4, dorsal kineties 1-4; Scale bars: 50μm (A-C).

Fig. 7. Morphology of Sterkiella tetracirrata from live (A-D) and protargol-impregnated (E, F) specimens. A, B, Ventral view of typical specimen live arrow denotes contractile vacuole (arrow); C, Ventral view of typical specimen; D, Ventral view showing macronuclear nod- ules(arrow) and micronuclei (arrowhead); E, F, Ventral and dorsal view of typical specimen; Scale bars: 50μm (C, E, F).

Fig. 8. Maximum likelihood (ML) phylogenetic tree inferred from 18S rDNA sequences of Oxytrichidae ciliates. The phylogenetic trees show the position of three soil ciliates of Oxytricha lithofera (arrow), Pleurotricha curdsi(arrowhead) and Sterkiella tetracirrata(double-arrowhead). New sequences are shown in bold text. Numbers at nodes indicate the bootstrap values of ML and the posterior probability of BI. Nodes designated by an asterisk (*) correspond to the supports not recovered in the estimated BI tree. The scale bar corresponds to two substitutions per 100 nucleotide positions.