INTRODUCTION

Compared to marine or freshwater ciliate species, soil ciliates are relatively under-studied. The diversity of soil ciliates has been a key issue in the argument of ciliate richness (Bamforth 1995; Foissner 1997). In our study, we sampled various soils and cultured them under laboratory environment to study the soil ciliate diversity of Korea. As a result, we described population of four soil ciliates from Korea.

MATERIALS AND METHODS

Samples were collected from surface soil around river delta in 2014. The ciliates were acquired using non-flooded Petri dish method described by Foissner (1987) and updated in Foissner, Agatha, and Berger (2002). The cells appeared several days after rewetting the sample. Ciliates were isolated using a micropipette. Individuals were observed in vivo using bright-field and differential interference contrast microscopy at 100-1000×magnifications. Protargol impregnation (Wilbert 1975; Foissner 1991) methods was used to reveal the infraciliature. Protargol was made in the lab according to Pan, Bourland & Song (2013). Counts, measurements, and drawings of stained specimens were performed with the aid of a camera lucida.

RESULTS AND DISCUSSION

Metopus hasei Sondheim, 1929 (Table 1, Fig. 1)

Systematics

Phylum Ciliophora Doflein 1901

Class Armophorea Lynn, 2004

Order Armophorida Jankowski, 1964

Family Metopidae Kahl, 1927

Genus Metopus Claparède & Lachmann, 1858

Material examined: Collected from surface soil of reeds field in Geum River estuary area. Sampled on June 6th, 2014. It was identified by Yingying He and deposited in Marine Ecology Laboratory, Inha University, Korea.

Description: Size in vivo about 55-95×14-25 μm, usually about 75×22 μm, body length: width ratio 3.9-6.9, on average 5.8 in protargol preparations (Table 1). Body outline elongate ellipsoidal, cells widest in mid-body. Preoral dome slightly sigmoidal and distinctly curved and slope to about 45° to main body axis, projecting knop-like above anterior left body margin, dorsoventrally flattened about 2 : 1. Postoral body portion cylindrical, with posterior body end slightly narrowed and rounded. Macronucleus elongate ellipsoidal, usually about 30×10 μm on average in protargol preparations, located underneath of adoral zone, contains numerous nucleoli (Fig. 1B, E, G). One micronucleus, globular to ellipsoidal, usually near or attached to anterior portion of macronucleus (Fig. 1E, G). Contractile vacuole in posterior body end (Fig. 1A, 1E). Cortex flexible, slightly furrowed by ciliary rows. Cytoplasm colourless, hyaline, packed with food vacuoles (Fig. 1A). Movement moderately fast by rotation about main body axis.

Somatic cilia about 10 μm long, those of perizonal stripe a little longer. The number of caudal cilia is from 4 to 6, with length about 3 μm. Perizonal ciliary stripe, of a usually structure, occupies about 26.8% of body length, and is slightly shorter than the adoral zone of membranelles (Table 1).

The adoral zone of membranelles is more or less spiralized, hardly roofed by preoral dome, and consist of 15-22 membranelles occupying about 34.9% of the body length. The paroral membrane is short (about 6 μm) and almost straight.

Remarks: This species seems to be a widely distributed species. It was discovered in mud from Madagascar (Sondheim 1929) and has been found in terrestrial habitats from all main biogeographical regions except Antarctica (Foissner 1998; Foissner and Agatha 1999), including Romania, Namibia, and so on. It prefers living in anaerobic environment and feeding on bacteria and is usually found in certain old cultures.

Urosomoida agiliformisFoissner, 1982 (Table 2, Fig. 2)

1982 Urosomoida agiliformis Foissner, Arch. Protistenk, 126: 117 (Fig. 112a-e; 1 slide of holotype and 1 slice of paratype specimens are deposited in the Oberösterreichische Landesmuseum in Linz, Austraia).

1983 Urosomoida agiliformis Foissner, 1982 - Foissner & Adam, Zool. Anz., 211: 161 (Fig. 113a-v).

1987 Urosomoida agiliformis Foissner, 1982 - Ganner, Foissner & Adam, Ann. Sci. nat., Zool., 8: 200, in part: population P1 (=population of Foissner 1982) and P2 (population of Foissner & Adam 1983); not population P3 and P4.

1996 Urosomoida agiliformis Foissner, 1982 - Wang & Song, J. Ocean Univ. Qingdao, 26: 179, Fig. 1A-J (reinvestigation of morphogenesis).

Systematics

Phylum Ciliophora Doflein 1901

Class Spirotrichea Bütschli, 1889

Order sporadotrichida Fauré-Fremiet, 1961

Family Oxytrichidae Ehrenberg, 1838

Genus Urosomoida Hemberger in Foissner, 1982

Material examined: This species was collected from soil of the Sorae Ecology Park on April 6th, 2014. It was identified by Yingying He and deposited in Marine Ecology Laboratory, Inha University, Korea.

Description: Body size in vivo about 70-90×25-35 μm, on average 76×30 μm, body length: width ratio 1.7-3.0, on average 2.5 in protargol preparations (Table 2). Body outline elongate ellipsoidal, with margins almost in parallel, both ends rounded, dorsoventrally flattened (Fig. 2A, E). Macronucleus elongate ellipsoidal, usually about 17.6×46.9 μm on average in protargol preparations (Table 2, Fig. 2E, G), located slightly to the left side of the body, contains numerous nucleoli (Fig. 2E, G). Micronuclei 2-4, globular to ellipsoidal, usually near or attached to macronucleus (Fig. 2E, G). Contractile vacuole to the left side of the cell (Fig. 2E), no collecting canals was observed (Fig. 2E). Cortex flexible. Cytoplasm colourless, hyaline, packed with food vacuoles and many yellowish crystals surrounded by tiny granules, no cortical granules was observed. Movement moderately rapid by crawling on substrate or swimming.

Adoral zone of membranelles about 30% of body length, and consists of about 22 membranelles. Buccal cavity narrow and flat. Frontal, transverse, and caudal cirri in life about 15 μm long, other cirri about 10 μm long. Frontventral cirri in V-shaped pattern. Three postoral ventral cirri in dense cluster behind buccal vertex. On average 4 transverse cirri. One right and 1 left marginal cirri row. Four dorsal kineties, the 4th dorsal kinety posterior end distinctly shortened, dorsal bristles about 3 μm long, three caudal cirri on kineties 1, 2, 3 respectively.

Remarks: This species seems to be a common species in terrestrial and freshwater environment. It has been found in various places around the world, including Austria, German, USA, France, and China.

Oxytricha proximataShibuya, 1930 (Table 3, Fig. 3)

1930 Oxytricha proximata Shibuya, J. imp.agric. Exp. Stn Nishigahara, 1: 209, 213 (Fig. 75).

1935 Oxytricha proximataShibuya, 1930 - Khal, Tierwelt Dtl., 30: 841.

Systematics

Phylum Ciliophora Doflein 1901

Class Spirotrichea Bütschli, 1889

Order sporadotrichida Fauré-Fremiet, 1961

Family Oxytrichidae Ehrenberg, 1838

Genus Oxytricha Bory De Saint-Vincent in Lamouroux,

Bory De Saint-Vincent & Deslongchamps, 1824

Material examined: Collected from surface soil of reeds field in Geum River estuary area. Sampled on June 6th, 2014. It was identified by Yingying He and deposited in Marine Ecology Laboratory, Inha University, Korea.

Description: Body size in vivo about 110-140×40-60 μm, protargol impregnated specimens about 110-141×39-63 μm, on average 126.4×48.9 μm, body length almost 2.6 times of body width (Table 3). Elongate ovate or elongate elliptical, posterior end obtusely pointed (Fig. 3E-G), dorsoventrally flattened (Fig. 3A). Two macronuclear nodules, Two macronucleus, elongate ellipsoidal, usually about 18.6×8.6 μm on average in protargol preparations (Table 3, Fig. 3E, G), located slightly to the left side of the body, contains numerous nucleoli (Fig. 3E, G). Micronuclei 2-3, globular to ellipsoidal, usually near or attached to macronucleus (Fig. 3E, G). Contractile vacuole to the left side of the cell (Fig. 2E), with two collecting canals pointing anteriorly and posteriorly respectively was (Fig. 3E). Cortex relatively flexible. Cytoplasm colourless, hyaline, packed with food vacuoles and many yellowish crystals surrounded by tiny granules. No cortical granules was observed. Movement moderately rapid by crawling on substrate or swimming.

Adoral zone of membranelles about 41% of body length, and consists of about 38 membranelles. Buccal cavity narrow and flat. Frontal, transverse, and caudal cirri in life about 15 μm long, other cirri about 12 μm long. Frontventral cirri in V-shaped pattern (Fig. 3B). Four postoral ventral cirri in dense cluster behind buccal vertex. On average 5 transverse cirri and pretransverse cirri (Fig. 3C). One right and 1 left marginal cirri row. Six dorsal kineties, the 5th and 6th dorsal kineties posterior end distinctly shortened, dorsal bristles about 3 μm long, three caudal cirri on kineties 1, 2, 4 respectively (Fig. 3D, G).

Remarks: The identity of this species with O. bimembranata cannot be excluded, because the original descriptions of these two species are both poor. According to the cell size and the portion of the adoral zone of membranelles, our species is more close to O. proximata. This species may be confined to terrestrial habitats (Berger 1999), it was firstly recorded in Japan (Shibuya 1930) and later in Belgium (Chardez 1967) and Hungary (Gellért 1956).

Cladotricha sp. in Nießen (1984)

Cladotricha nov. sp. - Nießen, Diploma thesis, p. 52, Abb. 15a-j, Table on p. 52 (Fig. 46a-r; description; slides likely deposited in the University of Bonn, Germany).

Systematics

Class Spirotrichea Bütschli, 1889 Order Stichotrichida Fauré-Fremiet, 1961 Family Kahliellidae Tuffrau, 1979 Genus Cladotricha Gaievskaïa, 1925

Material examined: This species was collected from saline soil of the Sorae Ecology Park on April 6th, 2014. The surface of the soil was covered with Suaeda. It was identified by Yingying He and deposited in Marine Ecology Laboratory, Inha University, Korea.

Description: Body size of protargol-impregnated specimens 76.2×22.8 μm on average (Table 4), length : width ratio about 3.3 : 1. Body not sigmoidal, anterior body end rounded, posterior body end tailed, dorsoventrally flattened (Fig. 4A, E). Two macronuclear nodules, elongate ellipsoidal, on average size 11.7×4.4 μm (Table 4, Fig. 4D, E, G), located slightly to the left side of the body, contains numerous nucleoli (Fig. 4E, G). Two to four micronuclei, size about 1.5-2 μm, globular to ellipsoidal, usually near or attached to macronucleus (Fig. 4E, G). Contractile vacuole to the left side of the cell (Fig. 4E), no collecting canals was observed (Fig. 4E). Cortex flexible. Cytoplasm colourless, hyaline, packed with food vacuoles and many yellowish crystals surrounded by tiny granules, cortical granules was observed under dorsal cortex, diameter about 0.8 μm. Movement moderately rapid by crawling on substrate or swimming.

Adoral zone basically in Gonostomum pattern (Berger 2011), occupies on average 42.7% of body length, and consists of about 25 membranelles. Buccal cavity narrow and flat. Frontal, transverse, and caudal cirri in life about 12 μm long, other cirri about 10 μm long. Three slightly enlarged frontal cirri. The frontoventral cirri row I consists of the left frontal cirrus. Frontoventral cirri row II, including the middle frontal cirrus, consists of about 3-4 cirri. Frontoventral cirri row III, including the right frontal cirri, consists of 3-4 cirri. Frontoventral cirri row IV starts right next to the row III, consists of 9-15 cirri, and extends to 69% of body length. Frontoventral cirri row V start next to adoral zone of membranelles, consists of 3-5 cirri (Table 4, Fig. 4F). Right marginal cirri row consists of on average 20 cirri, left marginal cirri row 16 cirri. And the right marginal cirri starts relatively posteriorly compared to gonostomum species. No transverse cirriThree dorsal kineties, dorsal bristles about 3 μm long, three caudal cirri (Table 4, Fig. 4).

Remarks: The genus Cladotricha is a poorly described genus. And Berger (2011) listed this species in this genus not as a valid publication. But our population is very much in accord with the characteristics of the genus and the species. But in Nießen (1984), she didn’t give this species name. And Berger (2011) thought this species may be a synonym of C. sigmoidea. But through our study, we can exclude this possibility, and we thought this species may need a name and redescription.