Dysteria nabia, Park & Min, 2014

Park, Mi Hyun & Min, Gi Sik, 2014, A New Marine Cyrtophorid Ciliate, Dysteria nabia nov. spec. (Ciliophora: Phyllopharyngea: Cyrtophorida: Dysteriidae), from South Korea, Acta Protozoologica 53 (3), pp. 257-268 : 258-267

Dysteria nabia nov. spec. ( Figs 1A–F , 2A–I , 3A–J; Table 1)

Diagnosis. Marine Dysteria , size approximately 94 × 45 µm in vivo; body oval to elliptical in outline; with five right kineties, the outermost two of which extend dorso-apically; the innermost right kinety conspicuous shortened; macronucleus about 33 × 15 µm in vivo; two ventral contractile vacuoles.

Type locality. Marine waters with mussels and seaweeds, Incheon Harbor (37°26′N, 126°35′E), the Yellow Sea, South Korea .

Other localities. Coastal waters, Ihoteu Beach (33°30′N, 126°28′E), Jeju-do Island , Korea strait, South Korea.

Type specimens. Two hapantotype slides (one with protargol-impregnated specimens, NIBRPR000 0104270; one with silver nitrate-impregnated specimens, NIBRPR0000104271) and two paratype slides (NIBRPR0000104272–NIBRPR0000104273) of protargol-impregnated specimens were deposited in the National Institute of Biological Resources , South Korea .

Etymology. The name originates from the Korean word “nabi” (meaning butterfly), indicating that this or- ganism moves like the sitting form of a butterfly folding its wings.

Description. Cell size 74–113 × 42–49 µm in vivo, on average 94 × 45 µm, body bilaterally flattened. Body outline usually oval to elliptical, ventral and dorsal sides almost parallel. In dividing cells, body form rectangular in outline. Anterior margin blunt, posterior region blunt or round. When observed from ventral view, left plate concave and right plate convex. Right plate slightly wider than left plate ( Figs 1A, B , 2A–C ). Un- der high magnification, one equatorial transverse strip positioned approximately at equatorial region on surface of both plates ( Figs 2C, D , 3B). Podite large and dagger-shaped, approximately 18 µm in length in vivo, subcaudally located on left ventral side ( Figs 1A–E , 2A–C ). Glandule located near the base of podite, approximately 8 µm in diameter ( Fig. 2E ; Table 1). Cilia restricted to ventral and apical grooves between left and right plates, approximately 12 µm long in vivo. Five right kineties even discernible in vivo ( Figs 1C, D , 2F , 3A). Cytoplasm colorless to grayish and light-brown, containing several food vacuoles, approximately 3–11 µm in diameter, and numerous small granules spread over the body ( Figs 1A, B , 2A–I ). Cytostome in anteri- or 1/6–1/7 of body, located ventrally. Cytopharynx conspicuous in vivo, longitudinally oriented and extending to posterior end of cell, supported by 2 relatively strong nematodesmal rods, tipped with one complex tooth ( Figs 1C, D , 3D). Two ventral contractile vacuoles, approximately 8 µm in diameter in vivo, one in anterior 1/3–1/4 of body, the other in posterior 1/3–1/4 of body ( Figs 1A–D , 2H , 3A, G). Macronucleus elongate and large, approximately 33 × 15 µm in vivo, positioned in body center, characteristically heteromerous, with the posterior part more hyaline than the anterior ( Figs 1A– D , 2E, G , 3A). Micronucleus not detected. Locomotion by slowly and wobbly crawling.

Infraciliature as shown in Figs 1C, D , 2F , 3A, C–I. Five right kineties, with the innermost row conspicuously shortened. Two outermost right kineties approximately equal in length, extending anteriorly to dorsal margin; the outermost kinety consisting of approximately 188 basal bodies (mookineties), comprising of 2–6 (average 4) basal body pairs (monokinety pairs). A single innermost right kinety, with 18–28 basal bodies, located in posterior 1/3–1/4 of body ( Figs 1C, D , 2F ). The remaining two right kineties gradually shortened from right to left ( Figs 1C, D , 2F , 3A). Five to seven left kineties, densely arranged close to right kineties, and positioned around equator ( Figs 1C, D , 3A, D). Terminal fragment antero-dorsally located, and forming hook-like shape comprising 6–10 basal bodies. Equatorial fragment composed of 10–33 basal bodies ( Table 1). Two to three basal body pairs antero-dorsally located under two outermost right kineties ( Figs 1C, D , 3C). Four to six kinetosome-like granules positioned near base of podite ( Figs 1C–E , 3A, G).

Arrangement of kineties in oral field typical of the genus: 2 parallel circumoral kineties slightly curved to left; preoral kinety obliquely positioned in anterior region; usually 3 left frontal kineties, located on right of circumoral kineties. Cirumoral kineties and preoral kinety consisting of dikinetids, and parallel left kineties composed of monokinetids ( Figs 1C–E , 3E, F, H–I). After protargol impregnation, several straight stripes were detected on surface of plates ( Fig. 3B).

Comparison. To date, 19 nominal Dysteria species have been investigated using silver impregnation methods. Among these, 12 species were referred to by Gong and Song (2004). The new species can be distinguished from other Dysteria species by its oval to elliptical body shape, body size, five right kineties with a single shortened innermost row, and macronucleus size.

Dysteria nabia closely resembles D. ovalis (Gourret and Roeser, 1886) Kahl, 1931 , D. pectinata (Nowlin, 1913) Kahl, 1931 , D. procera Kahl, 1931 , and D. proraefrons Clark, 1865 in terms of cell size, body shape, cytopharynx length, shortened innermost row of right kineties, and marine habitat. However, D. nabia differs from D. pectinata in several features, namely, its slightly larger body size (74–113 × 42–49 µm vs. 60–100 × 30–55 µm) and oval to elliptical body shape, with ventral and dorsal sides almost parallel (vs. body semi-oval in outline, with ventral side straight and dorsal convex). In addition, D. nabia has a groove on the posterior left lateral side from life (vs. no groove), fewer right kineties (5 vs. 7), and a larger number of basal bodies in the equatorial fragment (10–33 vs. 3–27) ( Table 2; Figs 4B, E–F ; Gong et al. 2007). Dysteria procera is similar in body size to D. nabia (80–110 × 25–40 µm vs. 74–113 × 42–49 µm), but has fewer right kineties (3 vs. 5) and fewer basal bodies in the equatorial fragment (3–15 vs. 10–33), and a smaller macronucleus (24–36 × 8–12 µm vs. 35–47 × 16–25 µm) ( Table 2; Figs 4G, H ; Gong and Song 2003). Dysteria proraefrons can also be distinguished from D. nabia by its slightly smaller body size (60–90 × 30–50 µm vs. 74–113 × 42–49 µm), a larger number of right kineties (6 vs. 5), smaller number of basal bodies in the equatorial fragment (2–11 vs. 10–33), and smaller macronucleus (20–45 × 6–15 µm vs. 35–47 × 16–25 µm) ( Table 2; Figs 4I, J ; Pan et al. 2011). Dysteria ovalis has 4 right kineties (vs. 5 in D. nabia ) and a different pattern of oral kineties ( Table 2; Figs 4B, C ; Fauré-Fremiet 1965).

Dysteria monostyla (Ehrenberg 1838) Kahl, 1931 , D. brasiliensis Faria et al., 1922 , D. calkinsi Kahl, 1931 , and D. antarctica Gong et al., 2002 have the same number of right kineties as D. nabia . However, unlike D. nabia , these four species do not have a shortened innermost right kinety ( Table 2; Figs 1C, D ; Petz et al. 1995; Song and Packroff 1997; Gong et al. 2002, 2007; Song and Willbert 2002).

Dysteria armata Huxley, 1957 , D. crassipes Claparède and Lachmann, 1859 , and D. lanceolata Claparède and Lachmann, 1859 have similar body size with D. nabia . However, D. armata has 6 right kineties (vs. 5) with 4 dorso-apically extended right kineties (vs. 2) ( Table 2; Figs 1C, D ; Fauré-Fremiet 1965). D. crassipes has fewer number of right kineties (4 vs. 5), smaller macronucleus (16–25 × 8–14 µm vs. 35–47 × 16–25 µm), and numerous ectosymbiotic bacteria on surface of plate (vs. absent) ( Table 2; Figs 1C, D ; Gong et al. 2007). D. lanceolata has different body shape (nearly oval or approximately rectangular vs. oval or ellipsoid), larger number of right kineties (6–7 vs. 5), and 2 or 3 of dorso-apically extended right kineties (vs. always 2) ( Table 2; Figs 1A–D , 2A–C ; Chen et al. 2011).

Dysteria nabia must also be compared with some of 17 earlier described species that have not been described by using modern methods. In the present study, we compared D. nabia with two closely related species that resemble the new species in terms of body size, number of contractile vacuoles, and absence of a dorsal spine. Dysteria meridionalis Dragesco, 1965 and D. astyla (Maskell, 1877) are very similar to D. nabia . Dysteria meridionalis closely resembles D. nabia in terms of length in vivo (96 μm vs. 74–113 µm) and the presence of two contractile vacuoles; however, it has 12 (vs. 5) right kineties ( Table 3; Figs 4B, L ; Dragesco 1966). Dysteria astyla is similar to D. nabia in terms of shape (oval vs. oval to elliptical) and the presence of two ventral contractile vacuoles; however, it has a smaller body (70 × 17.5 µm vs. 74–113 × 42–49 µm) and occurs in a different habitat (freshwater vs. marine). Dysteria astyla has no podite, whereas D. nabia has a conspicuous podite, approximately 18 μm long in vivo ( Table 3; Figs 4A, B, M ; Kahl 1931).

We further compared D. nabia with three other earlier described species, namely, Dysteria angustata (Claparède and Lachmann, 1858) , D. reesi Kahl, 1931 , and D. sulcata (Claparede and Lachmann, 1858) . The body size and infraciliature for D. angustata are not available, however, this species can be distinguished from D. nabia by its narrow, neck-like anterior margin whereas the ventral and dorsal sides of the anterior margin in D. nabia are parallel ( Table 3; Figs 4A, B, K ; Kahl 1931). Dysteria sulcata differs from D. nabia in its larger body size (150 µm vs. 74–113 × 42–49 µm) and presence of 4 ribs on the right plate (vs. no ribs) ( Table 3; Fig. 4O ; Kahl 1931). Dysteria reesi differs from D. nabia in its smaller body size (59–68 µm vs. 74–113 × 42–49 µm), conspicuous pigment spot in the left anterior end (vs. no spot), and location of the podite (posterior 1/4 of body vs. subcaudally) ( Table 3; Figs 2A–C , 4A, B, N ; Kahl 1931).

Molecular investigation and analysis. The SSU rDNA sequences of two populations of D. nabia are identical, with a length of 1,700 bp. The sequence was deposited in GenBank under accession numbers KF725634 and KF725635. The sequence similarity between D. nabia and other Dysteria species ranged from 91.5% ( D. crassipes ) to 98.4% ( D. pectinata ). Despite the low inter-specific similarity, with 91.5%, it is slightly higher than other inter-specific similarity among four Vorticella spp. , periphytic ciliates in the Peritrichs, ranging from 90.2 to 98.8%, identified by Gong et al. (2013). In the phylogenetic analysis, the family Dysteriidae was divided into two groups; however, the monophyly of this family was well supported, with high support values in the BI and ML analyses. Dysteria nabia formed a group with D. procera (96.4% in similarity) and D. pectinata (98.4%), while the remaining Dysteria species clustered as a second group ( Fig. 5 ). Results of our molecular analysis based on sequence divergence and the phylogenetic tree supports the designation of D. nabia nov. spec. as a distinct and novel ciliate belonging to the genus Dysteria .

Acknowledgments. This work was supported by the grants of Inha University and the program on Management of Marine Organisms causing Ecological Disturbance and Harmful Effects funded by KIMST/MOF.

Figures

Figs 1A–F. Morphology of Dysteria nabia nov. spec. from life (A, B), after protargol (C–E), and silver nitrate impregnation (F). The hapantotype (A–E) and paratype (F) specimens were investigated. A, B – left side view of two individuals with differing body size and shape; C, D – left side view showing the infraciliature, arrowheads indicate the kinetosome-like granules at the base of the podite; E – left side view of late-stage divider, showing the anlagen for the left kineties (arrows), the contractile vacuole pores (arrowheads), and the anlagen for terminal fragments in the opisthe (double-headed arrow); F – left side view showing the silverline system, arrowhead indicates the equatorial transverse stripe. Co – circumoral kineties, CVP – contractile vacuole pore, EF – equatorial fragment, Lf – left frontal kineties, LK – left kineties, Ma – macronucleus, P – podite, Pr – preoral kineties, RK – right kineties, TF – terminal fragment. Scale bars: 40 μm.

Figs 2A–I. Photomicrographs of living specimens of Dysteria nabia nov. spec. A, B – left lateral view of two typical individuals, arrows in (A) and (B) indicate the cytopharyngeal rod and podite, respectively, arrowheads indicate the groove on the left plate; C – left lateral view of an elongate specimen, arrow indicates the equatorial transverse stripe and arrowhead the groove on the left plate; D – left side view, arrow indicates the equatorial transverse stripe and arrowhead the complex teeth; E – left side view, arrow indicates the contractile vacuole pore and arrowhead the glandule; F – right kineties of the posterior portion, arrowheads indicate the innermost right kinety; G – left side view, arrow indicates the contractile vacuole pore and arrowhead the left kineties; H–I – left side view, arrowheads in (H) and (I) indicate the contractile vacuole pore and protuberances on the margins of the right kineties, respectively. Ma – macronucleus. Scale bars: 50 μm.

Figs 4A–O. Morphology and infraciliature of Dysteria nabia nov. spec. and closely related Dysteria species. A, B – D. nabia nov. spec. from life (A) and after protargol impregnation (B); C–D – D. ovalis (Gourret and Roeser, 1886) Kahl, 1931 (C, from Fauré-Fremiet 1965; D, from Kahl 1931); E–F – D. pectinata (Nowlin, 1913) Kahl, 1931 (from Gong et al. 2007); G–H – D. procera Kahl, 1931 (from Gong and Song 2003); I–J – D. proraefrons Clark, 1865 (from Pan et al. 2011); K – D. angustata (Claparede & Lachmann, 1858) (from Kahl 1931); L – D. meridionalis Dragesco, 1965 (from Dragesco 1966);M – D. astyla (Maskell, 1877) (from Kahl 1931); N – D. reesi Kahl, 1931 (from Kahl 1931); O – D. sulcata Claparede & Lachmann, 1858 (from Kahl 1931). Scale bars: 40 μm (A–B, I–J), 30 μm (E), 50 μm (G, L).

Fig. 5. Maximum likelihood tree based on SSU RNA gene sequences, showing the position of Dysteria nabia nov. spec (bold font). Numbers at the nodes represent the Bayesian posterior probability value and the bootstrap values from maximum likelihood. Solid circles represent full support in both algorithms.