Apokeronopsis sinica Liu et al., 2009

Choi, Ji Hye & Jung, Atef Omar and Jae-Ho, 2025, New record of four spirotrichs (Protozoa, Ciliophora) from South Korea, Journal of Species Research 14 (1), pp. 38-47 : 39-40

1. Apokeronopsis sinica Liu et al., 2009 ( Fig. 1 )

Material examined. Marine water (salinity 32.9‰, temperature 20.1℃) collected from Boritgol-gil, Gam- po-eup, Gyeongju-si, Gyeongsangbuk-do, South Korea (35°49 ʹ 35 ʺ N, 129°30 ʹ 37 ʺ E) on October 22, 2023 .

Diagnosis. Size 152-192 × 68-77 μm in vivo and 81- 129 × 36-54 μm after protargol impregnation (n =11); body elliptical with narrow posterior end; cytoplasm colorless; body flexible and non-contractile ( Fig. 1A- C ); contractile vacuole at 40% of body length ( Fig. 1C ); two types of cortical granules: smaller one colorless, about 0.2 μm in diameter, arranged in longitudinal rows, and larger one slightly yellowish, about 2 × 1 μm in size, scattered in whole body ( Fig. 1D, E ); adoral zone, composed of 45- 61 membranelles, occupies about 50% of body length in staining specimens; frontal cirri (bicorona) consist of 17- 26 cirri total, 8-12 in anterior corona, and 9-14 in posterior corona; two frontoterminal, 2-5 buccal, and 9-11 transverse cirri; midventral complex composed of 20-31 left and 22-33 right midventral cirri; one left (27-41 cirri) and one right (33-46) marginal cirral rows ( Fig. 1F ); three dorsal kineties ( Fig. 1G ); and about 100 macronucleus nodules, 4-7 micronuclei, distributed in whole body ( Fig. 1F, G ).

Distribution. Hong Kong (type locality, Liu et al., 2009), Korea (in this study).

Remarks. The Korean population of Apokeronopsis sinica is similar to the type population described by Liu et al. (2009) in most features except for body width (36- 54 μm vs. 72-105 μm after protargol impregnation; very likely resulted from different impregnation methods) ( Liu et al., 2009). Among Apokeronopsis species, A. antarctica (Petz, 1995) Shao et al., 2007 , A. crassa (Claparède and Lachmann, 1858) Shao et al., 2007 , and A. wrighti can be easily distinguished from A. sinica by possessing more than 20 transverse cirri (vs. less than 20) ( Shao et al., 2007; Long et al., 2008). Considering the number of transverse cirri, A. sinica is similar to A. bergeri and A. ovalis , which were already recorded in Korea by Jung et al. (2011). However, the Korean population of A. sinica differs from A. bergeri by the number of adoral membranelles (45-61 vs. 72-106), buccal cirri (2-5 vs. 9-15), transverse cirri (9-11 vs. 11-22), and left and right marginal cirri (27-41 vs. 44-70; 33-46 vs. 54-88) ( Li et al., 2008; Jung et al., 2011). Also, the body shape of A. bergeri differs from that of A. sinica in having an elongate to fusiform body with both ends broadly round- ed (vs. elliptical body with posterior end narrowed) ( Li et al., 2008). On the other hand, A. sinica can be distinguished from A. ovalis by the body size after protargol impregnation (81-129 × 36-54 μm vs. 120-175 × 55-90 μm) ( Shao et al., 2008, population I; Jung et al., 2011), the body shape (elliptical body with posterior end narrowed vs. oval to elliptical), and the color of the large cortical granules (slightly yellowish vs. green to yellow-greenish) ( Shao et al., 2008).

Voucher slides. Three slides with protargol-impregnat- ed specimens were deposited at the National Institute of Biological Resources (NIBRPR0000111269, NIBR PR 0000111270, NIBRPR0000111271).

Figures

Fig. 1. Apokeronopsis sinica in vivo (A-E) and after protargol impregnation (F, G). A, B. Ventral view showing the body shape. C. Dorsal view showing a contractile vacuole. D, E. Two types of cortical granules: smaller one (arrowhead) arranged in the longitudinal rows, and larger one (double-arrowhead) scattered in the whole body. F, G. Ventral (F) and dorsal (G) view showing the adoral zone of membranelles, midventral complex, the nuclear pattern, and three dorsal kineties. Arrowheads denote micronuclei. AZM, adoral zone of membranelles; BC, buccal cirri; CV, contractile vacuole; DK, dorsal kineties; FC, frontal cirri; FTC, frontoterminal cirri; LMR, left marginal row; LMVR, left midventral row; MA; macronuclear nodules; RMR, right marginal row; RMVR, right midventral row; TC, transverse cirri. Scale bars: 50 μm (A, B); 40μm (C); 20μm (F); 10μm (E); 5 μm (D).