Dysteria semilunaris ( Gourret & Roeser, 1888 )

Choi, Jung Min, Jung, Jae-Ho & Kim, Jung-Hoon Kang and Young-Ok, 2020, New record of four ciliates (Protozoa, Ciliophora) collected from rocky intertidal pools of South Korea, Journal of Species Research 9 (4), pp. 455-461 : 459-460

4. Dysteria semilunaris ( Gourret & Roeser, 1888)

Kahl, 1931 ( Fig. 5 )

Material examined. Marine water (temperature 12.0°C; salinity 33.0; pH 8.5) collected from the beach of Yullim village , Yullim-ri , Dolsan-eup, Yeosu-si, Jeollanam-do, South Korea (34°36′19″N 127°47′22″E) on April 21, 2012 ( Fig. 1 ; St. 3) .

Diagnosis. Body size 26-36 × 16-20 μm, length: width ratio about 1.7: 1, bilaterally flattened about 1: 2.1 in vivo; outline oval-shaped, broad anterior and narrowed posterior end of the cell, dorsal side convex than ventral side; conspicuous longitudinal grooves presented left and right plate; single macronucleus 14-20 × 6-10 μm in size; 2 longitudinally positioned contractile vacuoles near innermost row of right kineties; about 9 μm podite caudally positioned on left ventral side; 4-5 right kineties, including 2 frontoventral kineties of which extend dorso-apically; 1 short row below the anterior end of the frontoventral kineties; 6-7 left kineties; equatorial fragment composed of 5-9 basal bodies; terminal fragment anterodorsally located, composed of 3-5 basal bodies; 2 parallel circumoral kineties; 3 left frontal kineties; single-rowed preoral kinety.

Distribution. China, France, Germany, and Korea.

Remarks. The descriptions by Gourret and Roeser (1888) and Kahl (1931) did not provide detailed information of body size and infraciliature. Nevertheless, the D. semilunaris can be easily identified by the body shape and marine habitat. The Korean population of D. semilunaris differs from the two Chinese populations (Qingdao and Shanghai) in number of right kineties (4-5 vs. consistently 4 in both populations), presence of longitudinal groove (left and right plates vs. left only vs. right only), and transverse stripe at the equatorial region (absent in the Korean and Qingdao population vs. present in Shanghai population) ( Gong et al., 2007; Pan et al., 2016).

The closest congeners D. ovalis (Gourret and Roeser, 1886) Kahl, 1931 and D. crassipes Claparède & Lachmann, 1859 can be distinguished from D. semilunaris as follows: (1) absence of an extra short row below the anterior end of the frontoventral kineties; (2) absence of a longitudinal groove on the both plate; (3) subcaudally-located podite ( Gong et al., 2007; Park and Min, 2015; Pan et al., 2016). Additionally, D. calkinsi Kahl, 1931 differs from D. semilunaris in the following features: arrangement of contractile vacuoles (diagonally positioned in original description but not detected in Antarctic population vs. longitudinally positioned); number of groove on the left plate (two vs. one); extra short row below the end of frontoventral kineties (absent vs. present); number of left frontal kineties (two vs. three) ( Kahl, 1931; Song and Wilbert, 2002; Gong et al., 2007).

Voucher slides. Two slides with protargol-impregnated specimens was deposited at National Institute of Biological Resources (NIBRPR0000110832) and Korea Institute of Ocean Science and Technology (KIOST), respectively.

Figures

Fig. 5. Photomicrographs of Dysteria semilunaris from living specimens (A-D) and protargol impregnated specimens (E, F). A. Left lateral view of typical individual. B. longitudinal groove on left plate (arrowheads). C. Ventral view. D. Right lateral view showing the two contractile vacuoles (arrows) and the longitudinal groove on the right plate (arrowheads). E, F. Left views of stained specimens showing infraciliature, arrow denotes the short row below the end of the frontoventral kineties. Co, circumoral kineties; CVP, contractile vacuole pore; Cy, cytopharynx; EF, equatorial fragment; FVK, frontoventral kineties; LF, left frontal kineties; LK, left kineties; Ma, macronucleus; P, podite; Pr, preoral kinety; RK, right kineties; TF, terminal fragment. Scale bars: 20μm.

Fig. 1. Map of the sampling stations in South Korea. Each station (marked with red circles) located at three intertidal zones of the Korean Peninsula (St. 1-3) and Baekdo Island (St. 4).