Metopus setosus Kahl, 1927

Jung, Atef Omar and Jae-Ho, 2022, New record of five anaerobic ciliate species from South Korea, Journal of Species Research 11 (2), pp. 108-116 : 111-112

3. Metopus setosus Kahl, 1927 ( Fig. 3 )

Material examined. Freshwater sample collected from Bunhwangji , Nakdong-myeon, Sangju-si, Gyeongsang- buk-do, Republic of Korea (36°23′50.4″N, 128°15′47.7″E) on 26 April 2021 .

Diagnosis. Size 45-70 × 20-30 μm in vivo and 35-50 × 12-16 μm after protargol impregnation (n = 6); body obovate, slightly obconical, distinctly twisted anteriorly, left side convex and right side concave; preoral dome distinctly convex, slightly overhangs on left side, extends to half body length; one ellipsoidal macronucleus about 14 × 7 μm in size after protargol impregnation and one micronucleus about 3 μm across anterior to mid-body; contractile vacuole very large, in posterior body end; cortex flexible, furrowed along ciliary rows, cortical granules arranged in rows between ciliary rows; cytoplasm colorless, few to many lipid droplets and food vacuoles contain bacteria; on average 22 dikinetidal ciliary rows, somatic cilia 10-12 μm long, caudal cilia as long as or longer than body; perizonal stripe consists of 5 rows, rows 1-3 very close together and their dikinetids arranged in false kineties; adoral zone comprises 20 membranelles on average.

World distribution. Australia, China, Germany, and South Korea ( Kahl, 1932; Wang and Nie, 1935; Foissner, 1980; Esteban et al., 1995; Foissner et al., 2002; Vd’ačný and Foissner, 2017a).

Remarks. The Korean population of Metopus setosus agrees to the most recent description of Vd’ačný and Foissner (2017a) and to a Chinese population studied by Wang and Nie (1935) in most features. Metopus setosus could be confused with the small species with long caudal cilia such as M. minor , M. recurvatus and M. setifer . Metopus setosus differs from M. minor by the larger body size (54-60 vs. 30-40 μm) and the higher number of ciliary rows (22 vs. 10). Metopus recurvatus was considered a junior synonym of M. minor by Foissner (1980). Metopus setifer is also similar to M. setosus in the body size, but they differ mainly in the body shape and the ciliary rows number ( Kahl, 1932; Foissner, 1980; Esteban et al., 1995; Foissner et al., 2002; Vd’ačný and Foissner, 2017a).

Voucher slide. One slide with protargol-impregnated specimens was deposited at the National Institute of Biological Resources (NIBRPR0000111064).

Figures

Fig. 3. Metopus setosus in life (A-C), in the scanning electron microscope (D-F), and after protargol impregnation (G, H).A-C. Ventral (A) and ventrolateral (B, C) views showing the torsion of the body, the adoral zone of membranelles, the very long caudal cilia, and the large, terminal contractile vacuole. D-F. Dorsal (D, E) and ventrolateral (F) view, showing the body shape, the somatic ciliature, and the very long caudal cilia. G, H. Ventral and dorsal view showing the somatic and oral ciliature, the perizonal ciliary stripe, and the nuclear apparatus. AZP, adoral zone of polykinetids; CC, caudal cilia; CV, contractile vacuole; MA, macronucleus; PM, paroral membrane; PS, perizonal ciliary stripe. Scale bars 30 μm (A-D) and 20μm (E-H).