New record of three oxytrichid ciliates (Ciliophora: Oxytrichidae) from South Korea Author Min, Kyu-Seok Chae and Gi-Sik mingisik@inha.ac.kr text Journal of Species Research 2022 11 4 287 295 journal article 10.12651/JSR.2022.11.4.287 2713-8615 13138793 1. Oxytricha lithofera Foissner, 2016 ( Table 1 , Figs. 1 and 2 ) Oxytricha lithofera Foissner, 2016 : p. 699 ; Luo et al. , 2021 : p. 1 . Korean name. qǐặšAEǿAEệ Material examined. Slightly saline soil (1‰), Sacheonsi , Gyeongsangnam-do , South Korea ( 34°57 ʹ 42.6 ʺ N , 128°02 ʹ 15.2 ʺ E ), collected by Kyu-Seok Chae in June 2020 . Diagnosis of the Korean population. Size in vivo about 100 × 45 μm, ellipsoidal body shape; 2 macronuclear nodules and 1-3 micronuclei; contractile vacuole at the left of mid-body; 21-28 adoral membranelles; cortical granules present; 3 frontal cirri; 4 frontoventral cirri; one buccal cirrus; 3 postoral-ventral cirri; 2 pretransverse and 5 transverse cirri; one left and one right marginal cirral row; 4 dorsal and 2 dorsomarginal kineties; 3 caudal cirri. Description. Body size 90-110 × 40-50 μm in vivo , 67- 88 × 25-40 μm after protargol preparations ( Table 1 ). Flexible body outline usually elongated elliptical, both ends rounded ( Fig. 1A ). Two macronuclear nodules, with a size of 11-16× 5-8 μm after protargol preparation ( Fig. 1C ). One to three micronuclei, size about 2 μm diameter after protargol preparation ( Fig. 1C ). Contractile vacuole in left margin of mid-body, about 11 μm in diameter ( Fig. 2A , arrowhead). Colorless cortical granules usually arranged along and in between dorsal kineties ( Fig. 2B ). One or two ring-shaped lithosomes, 4-6 μm in diameter, with wall 0.8-1.2 μm thick, located subapically and/or subterminally ( Figs. 1A , 2A ). Cytoplasm colorless ( Fig. 2C ). Adoral zone membranelles along about 38% of body length, comprising of 21-33 membranelles ( Figs. 1B , 2C , Table 1 ). Three frontal cirri, four frontoventral cirri, one buccal cirrus, and three postoral-ventral cirri ( Figs. 1B , 2C , Table 1 ). Two pretransverse and five transverse cirri ( Figs. 1B , 2C , Table 1 ). One left (14-21 cirri) and right (15-18 cirri) marginal row, both marginal rows non-confluent posteriorly ( Fig. 1B , Table 1 ). Four dorsal and two dorsomarginal kineties ( Figs. 1C , 2D , Table 1 ). Three caudal cirri located at ends of dorsal kineties 1, 2, 4 on posterior end of cell ( Figs. 1C , 2D ). AM, adoral membranelles; BC, buccal cirrus; CV, coefficient of variation in %; DK, dorsal kineties; DM, dorsomarginal row; FC, frontal cirri; FVC, frontoventral cirri; LMC, left marginal cirri; Ma, macronuclear nodules; Max, maximum; Mi, micronuclei; Min, minimum; n, number of specimens examined; PTC, pretransverse cirrus; PVC, postoral ventral cirri; RMC, right marginal cirri; SD, standard deviation; SE, standard error of the arithmetic mean; TC, transverse cirri. Distribution. Austria , China , Venezuela , and South Korea (This study). Remarks. Cell body outline and distributional pattern of cirri in O. lithofera are similar to those of O. siseris Vuxanovici, 1963 . However, O. lithofera differs from O. siseris in the number of right marginal cirri (15-18 vs. 10-14) and lithosomes (present vs. absent) ( Foissner, 2016 ; Vuxanovici, 1963 ). Apart from the similarity between the Chinese population and most samples of the Korean population by the one-bristle-wide gap in dorsal kinety 1, this character generally serves as an important feature that can be used to distinguish O. lithofera from other Oxytricha species ( Foissner, 2016 ). a Data based on randomly selected, protargol-stained specimens. Fig. 1. Morphology of Oxytricha lithofera from live (A) and protargol-impregnated (B, C) specimens. A, Ventral view arrowheads denote lithosomes; B, C, Ventral and dorsal view of typical specimen; AZM, adoral zone of membranelles; BC, buccal cirrus; CC, caudal cirri; E, endoral membrane; FC, frontal cirri; LMR, left marginal cirral row; Ma, macronuclear nodules; Mi, micronuclei; P, paroral membrane; RMR, right marginal cirral row; TC, transverse cirri; 1-6, dorsal kineties 1-6; Scale bars: 50 μm (A, C). Fig. 2. Photomicrographs of Oxytricha lithofera from live (A, B) and after protargol impregnation (C, D). A, Ventral view showing lithosomes (arrows) and contractile vacuole (arrowhead); B, Dorsal view showing dorsal bristles and cortical granules; C, D, Ventral and dorsal view of typical specimen; Scale bars: 50 μm (A- D). Fig. 3. Morphology of Pleurotricha curdsi from live (A) and protargol-impregnated (B, C) specimens. A, Ventral view of typical specimen live arrow denotes contractile vacuole (arrow); B, C, Ventral and dorsal view of typical specimen; AZM, adoral zone of membranelles; BC, buccal cirri; CC, caudal cirri; DM, dorsomarginal row; DK, dorsal kinety; E, endoral membrane; FC, frontal cirri; FVC, frontoventral cirri; LMR, left marginal cirral row; Ma, macronuclear nodules; Mi, micronuclei; P, paroral membrane; PTC, pretransverse cirri; PVC, postoral ventral cirri; RMR, right marginal cirral row; TC, transverse cirri; 1-4, dorsal kineties 1-4; Scale bars: 50 μm (A- C). The Korean population of O. lithofera corresponds to the type population from Venezuela based on the body size, cirri pattern, number of macronuclear nodules, and micronucleus, up to 10 μm long dorsal bristles and mito- chondria-like granules present. However, they differ in the number of adoral zone of membranelles (21-33 vs. 19-21) and the number of left and right marginal cirri (14-21 and 15-18 vs. 12-15 and 9-12) ( Foissner, 2016 ). However, the Korean population differs from the type population with regards to the absence of a one-bristle-wide gap in dorsal kinety 1 in most samples, which is present in the latter population. In addition, the Korean population differs with respect to the size of micronucleus (about 2 μm in diameter vs. about 4 μm in diameter) and habitats (saline soil, 1‰ vs. brackish water, 3‰) of the Chinese population ( Luo et al. , 2021 ). In addition, the Korean and Chinese population differ from the type population with regards to the absence of a one-bristle-wide gap in dorsal kinety 1 in most samples, which is present in the latter population. The 18S rDNA gene sequence of the Korean O. lithofera was 1770 bp in length (GenBank accession number: OM212987). The Korean and Chinese populations formed a clade with high support (100% ML, 0.99 BI) in the phylogenetic tree (arrow in Fig. 8 ), with 0.12% genetic divergence (2 nt difference). Deposition. The voucher slide with protargol-impregnat- ed specimens is deposited in the National Institute of Biological Resources in Korea (NIBRPR0000110853).