INTRODUCTION

To date, more than 240 ciliate species (including parasitic ciliates), mainly belonging to the class Spirotrichea, have been reported from Korea (The Korean Society of Systematic Zoology 1997; Kwon 2009; Jung et al. 2012; Shin 2012; Jung 2013; Park and Min 2014; Lee et al. 2015; Nam et al. 2015 etc).

Most species of dysteriid ciliates (Ciliophora: Phyllopharyngea) are found in marine benthic habitats. Dysteria species are characterized by a laterally flattened body shape, oral structure with conspicuous cytopharynx, and restricted ciliature in the anterior and ventral regions (Kahl 1931; Deroux 1965; Dragesco 1966; Wilbert 1971; Song and Wilbert 2002; Chen et al. 2011). To date, more than 30 Dysteria morphospecies have been investigated (Fauré-Fremiet 1965; Petz et al. 1995; Gong et al. 2002, 2003, 2007; Song and Wilbert 2002; Gong and Song 2003, 2004; Hu and Suzuki 2005; Wilbert and Song 2005; Chen et al. 2011; Pan et al. 2011; Park and Min 2014). However, only one species - Dysteria nabia Park & Min, 2014 - has previously been recorded in Korea.

MATERIALS AND METHODS

Sample collection, observation, and identification

The dysteriid ciliates were collected by filtering the washed seawaters of mussels and seaweeds that were sampled from harbors. The obtained samples were maintained in Petri dishes at room temperature. We observed the specimens by using bright-field and differential interference contrast microscopy, at magnifications of ×50 to ×1000. We used the protocol of Foissner (1991) to reveal the infraciliature. We used the Chatton-Lwoff method to reveal the silverline systems for the three dysteriids (Corliss 1953). We counted and measured the stained specimens at a magnification of ×1000 (DM2500; Leica, Wetzlar, Germany). Terminology follows that of Corliss (1979), Gong and Song (2004), and Chen et al. (2011).

All specimens were deposited in the National Institute of Biological Resources (NIBR), Korea.

RESULTS AND DISCUSSION

Class Phyllopharyngea de Puytorac et al., 1974

Order Dysteriida Deroux, 1970

Family Dysteriidae Claparède & Lachmann, 1858

Genus Dysteria Huxley, 1857 납작충속

1.D ysteria brasiliensisFaria et al., 1922 꼬리납작충 (Fig. 1A-K; Table 1)

Dysteria brasiliensisFaria et al. 1922, p. 196, Fig. 25; Gong et al. 2007, p. 157, Figs. 8-9.

Material examined: On September 27, 2011 at Incheon Harbor, the Yellow Sea, Korea (37°26′N, 126°35′E).

Diagnosis: (i) Normal type: Marine Dysteria, size approximately 105 μm×47 μm in vivo; dorsal spine present; six right kineties; macronucleus approximately 33 μm×15 μm in vivo; two ventral contractile vacuoles; ectosymbiotic bacteria rod-shaped.

(ii) Small-sized type: Marine Dysteria, size approximately 59 μm×33 μm in vivo; dorsal spine absent; five right kineties; macronucleus approximately 23 μm×13 μm in vivo; two ventral contractile vacuoles; ectosymbiotic bacteria rod-shaped.

Remarks: This species was originally reported by Faria et al. (1922). Gong et al. (2007) re-described the species as three types (normal type, small-sized type, and elongate type) according to size and body outline. In the present study, we identified two types of D. brasiliensis, i.e., normal and small-sized type, in the same population; our normal and small-sized types correspond well with the two previously described types of Chinese isolate (Gong et al. 2007). However, the normal type in our population differs from that of the Chinese isolate in terms of the cell size and number of right kineties - cell size approximately 90~126 μm×44~52 μm in our population and 120~140 μm×46~60 μm in the Chinese isolate; six right kineties in our population and five right kineties in the Chinese isolate (Table 1, Fig. 1A-K; Gong et al. 2007). We considered the slightly different cell size and number of right kineties to be variations of D. brasiliensis.

Habitat: Marine waters with mussels and seaweeds.

World distribution: Brazil, China, Korea.

Deposition: NIBRPR0000106074-NIBRPR0000106075.

Identifiers: Mi-Hyun Park and Gi-Sik Min.

2.D ysteria lanceolata Claparède and Lachmann, 1859 창납작충 (신칭) (Figs. 2A-H; Table 2)

Dysteria laceolataChen et al. 2011, p. 106, Figs. 1-34.

Material examined: On February 9, 2011 at Incheon Harbor, the Yellow Sea, Korea (37°26′N, 126°35′E).

Diagnosis: Cell size approximately 51 μm×37 μm in vivo; body oval in outline; seven to eight right kineties, three outermost kineties extending to dorso-apically; macronucleus 23 μm×15 μm in vivo; two ventral contractile vacuoles.

Remarks: Dysteria lanceolata was recently collected from China and was re-described by Chen et al. (2011) based on its body shape, size, and infraciliature. The D. lanceolata isolate identified in our present study is slightly smaller than the Chinese isolate (49~53 μm×34~38 μm vs. 60~80 μm ×30~60 μm) in vivo and has seven to eight right kineties (vs. six to seven right kineties in the Chinese isolate). However, most other features correspond well with those of the Chinese isolate as follows: oval body shape; presence of groove and rod-shaped ectosymbiotic bacteria on surface of plate; and three frontoventral kineties (cf. two to three in Chinese isolate) (Table 2, Fig. 2A-H; Chen et al. 2011).

Habitat: Marine waters with mussels and seaweeds.

World distribution: France, China, Korea.

Deposition: NIBRPR0000106076-NIBRPR0000106077.

Identifiers: Mi-Hyun Park and Gi-Sik Min.

3Dysteria nabia Park & Min, 2014 나비납작충 (신칭)

Dysteria nabia Park & Min 2014, p. 258, Figs. 1A-F, 2A-I, 3A-J.

3.D ysteria ovalis (Gourret and Roeser, 1886) Kahl, 1931 둥근납작충 (신칭) (Fig. 3A, D-H; Table 2)

Dysteria ovalisKahl 1931, p. 256, Figs. S 252, 7; Fauré- Fremiet 1965, p. 6681, Fig. 11.

Material examined: On September 25, 2008 at Geojin Harbor, Gangwon-do, the East Sea, Korea (salinity, 32.3 psu; temperature, 22.6°C; pH 8.0; 38°26′N, 128°27′E).

Diagnosis: Cell size approximately 58 μm×29 μm; body oval in outline; four right kineties, one innermost kinety conspicuously shortened; macronucleus 19 μm×13 μm in vivo; two ventral contractile vacuoles. Silverlines show irregular and rather large reticulate, with equatorial transverse stripe.

Remarks: Dysteria ovalis was originally reported by Gourret and Roeser (1886) and was subsequently described by Kahl (1931) (Fig. 3B, C). After then, Fauré-Fremiet (1965) described the infraciliature of D. ovalis. Our population corresponds well with the isolate reported by Fauré-Fremiet (1965) in terms of the cell size, infraciliature, and silverline structure (Table 2, Fig. 3A-H; Kahl 1931, Fauré-Fremiet 1965).

Habitat: Marine waters with mussels and seaweeds.

World distribution: France, Korea.

Deposition: NIBRPR0000106078-NIBRPR0000106079.

Identifiers: Mi-Hyun Park and Gi-Sik Min.

Key to the Korean species of the genus Dysteria

1. Four right kineties······························································ ··············D. ovalis (Gourret and Roeser, 1886) Kahl, 1931 - More than four right kineties············································2

2. Five or six right kineties···················································3 - More than six right kineties················································ ··················D. lanceolata Claparède and Lachmann, 1859

3. Right kinety 5 terminates anteriorly in posterior 1/4 of body········································D. nabia Park & Min, 2014 - Right kinety 5 or 6 terminates anteriorly at cytostome level or over equatorial transverse stripe··························· ········································D. brasiliensisFaria et al., 1922