Redescriptions of Five Species of Marine Peritrichs, Zoothamnium Plumula, Zoothamnium Nii, Zoothamnium Wang, Pseudovorticella Bi

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Redescriptions of five species of marine peritrichs, Zoothamnium plumula, Zoothamnium nii, Zoothamnium wang, Pseudovorticella bidulphiae, and Pseudovorticella marina (Protista, Ciliophora)

DAODE JI1, MANN KYOON SHIN2, JOONG KI CHOI3, JOHN C. CLAMP4, KHALED A. S. AL-RASHEID5 & WEIBO SONG6,7 1School of Ocean, Yantai University, Yantai 264005, China 2Laboratory of Protozoology, Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China 3Department of Biological Science, University of Ulsan, Ulsan 680-749, Korea 4Department of Biological Sciences, Inha University, Incheon 402-751, Korea 5Department of Biology, North Carolina Central University, Durham, North Carolina 27707, USA 6Zoology Department, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia 7Corresponding author. E-mail: [email protected]

Abstract

The significant similarity of congeners and an accumulation of inaccurate descriptions or misinterpretations in previous studies can make it difficult to separate species of peritrich ciliates from one another. Isolates collected from Chinese coastal waters allowed investigation and redescription of three marine species of peritrichs, Zoothamnium plumula Kahl, 1933, Z. nii Ji et al., 2005 and Z. wangi Ji et al., 2005, emphasizing in particular details of characters observed in vivo, infraciliature and comparisons with morphologically similar congeners. Brief redescriptions based on new material also are provided for two other marine peritrichs, Pseudovorticella bidulphiae (Stiller, 1939) Ji et al., 2009 and P. m a ri na (Gre- eff, 1870) Ji et al., 2009.

Key words: Peritrichia, Zoothamnium, Pseudovorticella, morphology, marine ciliate

Introduction

The subclass Peritrichia is one of the two largest and taxonomically diverse groups of ciliates, containing over 1000 nominal species (Kahl 1933, 1935; Kent 1880–1882; Song 1986, 1991; Stiller 1971). Identification of peritrichs is frequently very difficult because congeners in larger genera are often very similar in their morphology, with over- lapping characteristics in many cases, and inaccurate or incomplete descriptions with misinterpretation of characteristics or misidentifications of taxa have accumulated in the taxonomic literature over the years. In recent years, details of the infraciliature and silverline system have been used in more and more taxonomic studies of peritrichs to identify and separate species within genera. These characteristics are species-specific, but exhibit high variability among congeners (Clamp 1992, 1993, 1994, 1997, 2005, 2006; Foissner et al. 1992; Ji & Kusuoka 2009; Ji & Song 2004; Ji et al. 2004, 2005a-c, 2006a, b, 2009; Norf & Foissner 2010; Sun et al. 2005, 2006a, b, 2007; Wu et al. 2011). The techniques of silver staining needed to observe both types of characters are not easy to master on a consistent level, even for experts, but the results are worth the effort because reliable taxonomic identifications based on morphology provide a firm support for related molecular phylogenetic studies and identification of species by matching DNA sequences (Chen et al. 2010; Clamp & Williams 2006; Foissner et al. 2009; Hu et al. 2009; Li et al. 2008; Sun et al. 2010, 2011; Zhan et al. 2009). In the present study, three marine peritrichs, Zoothamnium plumula Kahl, 1933, Z. nii Ji et al., 2005 and Z. wangi Ji et al., 2005, which were reported in recent studies, but not described fully owing to insufficient material (Ji et al. 2005c; Song et al. 2002), were reinvestigated with new material to describe details of the morphology of

Accepted by A. Wright: 24 May 2011; published: 27 Jun. 2011 47 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. living specimens and their infraciliatures. Additionally, new specimens of two species of Pseudovorticella, P. bidulphiae (Stiller, 1939) Ji et al., 2009 and P. m a r in a (Greeff, 1870) Ji et al., 2009, were also redescribed.

Material and methods

Collection of samples. Samples were collected from a shrimp-farming pond in the region of Qingdao, Shandong Province, P.R. China, (36º16’N; 120º39’E) using glass slides as artificial substrates. Slides were fixed to a frame, immersed in water for 10 days to allow colonization by peritrichs, retrieved, and transported to the laboratory for examination. Observations. Living ciliates were observed using bright field and differential interference contrast micros- copy. Specimens were stained with protargol according to the method of Wilbert (1975) to reveal the infraciliature. The “dry” (Foissner 1976) and “wet” (Song & Wilbert 1995) silver nitrate methods were used to demonstrate the silverline system. Deposition of slides. Type specimens of Z. nii and Z. wangi were not deposited as part of their original descriptions. However, slide preparations of specimens used in this study had been kept in the Laboratory of Proto- zoology, Institute of Evolution and Marine Biodiversity, Ocean University of China (OUC), and we selected three slides of each species as types. Types were assigned as follows and deposited in the collections of the aforemen- tioned laboratory: Z. nii, lectotype with registry number 0406280101(protargol preparation) and paralectotypes with registry number 0406280102 (dry silver nitrate preparations); Z. wangi, lectotype with registry number 0208050101 (protargol preparation) and paralectotypes with registry number 0208050102 (dry silver nitrate preparations). No types of P. bidulphiae and P. marina were designated in their original descriptions because both were based upon observations of living material. Two slides of P. bidulphiae with registry numbers 2005: 3: 24: 1 (protargol preparation) and 2005: 3: 24: 2 (dry silver nitrate preparation) and one slide of P. m ar in a with registry number 2005: 3: 24: 4, (protargol preparation) were deposited as voucher specimens in the Natural History Museum of London. A second voucher slide of P. m a r in a with registry number 0208100102 (dry silver nitrate preparation) was deposited in the collection of OUC. Two voucher slides of Z. plumula with registry numbers 0206280201 (protargol preparation) and 0206280202 (dry silver nitrate preparation) were deposited in the collection of OUC.

Results

Song et al. (2002) did a relatively detailed investigation of Zoothamnium plumula, but its infraciliature, especially the detailed pattern of infundibular polykineties, was not fully described. Using new material, we were able to describe the infraciliature and provide clear photomicrographs of living specimens. Both Z. nii and Z. wangi were described originally in Chinese with superficial treatment of their morphology (Ji et al. 2005c), and we were able to give detailed redescriptions and emended diagnoses for them here.

Zoothamnium plumula Kahl, 1933 (Fig. 1; Table 1)

Emended diagnosis. Marine Zoothamnium with colony up to 3 mm high; elongate, median primary stalk giving rise to secondary stalks in regular alternate series in single plane to create feather-shaped outline. Zooids conical to vase-shaped, measuring 50–75 × 35–45 µm in vivo; peristomial lip thick, without medial, circumferential infolding when expanded. Macronucleus C-shaped, transversely oriented, located in oral half of cell. Pellicular striations closely spaced and indistinct at lower magnifications; 50–70 silverlines lying between peristomial lip and trochal band and 20–30 between trochal band and scopula. P3 consists of three rows of kinetosomes that are equal in length; row 1 separated from rows 2 and 3 by gap in abstomal quarter and all three rows converging adstomally. Redescription. Colony large, up to 3 mm tall and including over 500 zooids. Secondary stalks up to 800µm long, branching off elongate primary stalk in regular, alternate series in one plane; tertiary stalks with same pattern

48 · Zootaxa 2930 © 2011 Magnolia Press JI ET AL. TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. of branching, measuring less than 120µm in length (Figs. 1B, D–F, J). Secondary stalks increasing slightly in length from most basal ones to medial region of colony and then decreasing in length toward tip of colony to create feather-shaped outline. Occasionally, most basal secondary stalk more highly developed and considerably longer than other secondary stalks (Fig. 1D). Stalk with diameter of 16 µm in basal portion of primary stalk, narrowing progressively to diameter of 8 µm at distal ends of tertiary stalks; cortex of stalk colorless and transparent, with smooth surface and fine longitudinal striations in interior. Spasmoneme relatively more dense than cortex of stalk, with diameter of 5–6 µm in primary stalk, narrowing progressively to diameter of 2.5 µm at distal ends of tertiary stalks; band of mitochondria, visible as dark granules with diameter of 0.8 µm, winding along helical path just beneath surface of spasmoneme (Fig. 1L). Colony relatively insensitive to stimulation, requiring strong turbulence or excitation to initiate full contraction of entire colony, usually contracting only partially when touched with nee- dle. Zooids elongate, subconical, usually 50–75 µm (n=11) long; body widest at peristomial lip, which measures 35–45 µm (n=11) in diameter (Figs. 1A, K). Small number of enlarged zooids (macrozooid?) measuring up to 90– 100 × 50–60 µm usually present on middle or distal parts of secondary stalks (Figs. 1B, F, J). Body slightly con- stricted below peristomial lip, which lacks a secondary, circumferential infolding (compare with Fig. 2A); epistomial disc moderately elevated above peristomial lip (Fig. 1A). Pellicular striations easily visible above × 400 magnification (Fig. 1M), but surface of body appears uniformly smooth at low magnifications. Telotroch discoid, measuring 25–30µm x 50–60 µm. Cytoplasm of zooids packed with tiny (0.8–1.5 µm diameter), dense granules visible only at high magnification (×1000); cell colorless or slightly grayish at low magnifications. Food vacuoles and items of food within them vari- able in size, randomly distributed in body. Single contractile vacuole in adoral position beneath epistomial disc and near dorsal wall of infundibulum. Macronucleus C-shaped, transversely oriented, surrounding micronucleus and lower half of infundibulum (Fig. 1A). Oral infraciliature as shown in Figures 1H, I, N-P. Haplo- and polykinety making one and one-quarter circuits around peristome and one additional circuit within infundibulum. Haplokinety and polykinety parallel on peristome, diverging within infundibulum to lie on opposite walls (Fig. 1H). Epistomial membrane short, located at entrance into infundibulum (arrows in Figs. 1H, P). Germinal kinety running parallel to haplokinety in adoral half of infundibulum (Figs. 1H, O, arrow). Each of three infundibular polykineties (P1–P3) consisting of three rows of kinetosomes. All rows of Pl terminating adstomally at level of cytostome; rows of P2 terminating adstomally at adstomal curvature of P1. Rows of P2 terminating abstomally without merging with P1; abstomal 1/4 of row 3 of P2 diverging from other rows of P2 (Figs. 1H, I, N). All rows of P3 terminating adstomally at point slightly beyond adstomal end of P2 and abstomally at point approximately 1/3 of distance from adstomal to abstomal end of P2. Rows 2 and 3 of P3 closely parallel to row 1 in adstomal half, diverging from it in abstomal half, converging again with it at abstomal end of P3 (Fig. 1I ). Trochal band consisting of band of dikinetids encircling cell at point 3/4 of distance from peristome to scopula. Silverline system consisting of closely spaced, parallel, transverse silverlines (Figs. 1G, Q); 50–60 silverlines present between peristome and trochal band, 22–27 between trochal band and scopula. Pellicular pores sparsely distributed alongside silverlines (Fig. 1Q) Remarks. The Chinese population of Z. plumula that we examined is characterized mainly by the following characters: alternately branched stalk, feather-shaped outline of colony, presence of larger zooids at some points on secondary stalks, and marine habitat. Characteristics of the colonies that we observed matched well with both the original description by Kahl (1933, 1935; Figs. 1B, C) and the redescription by Song et al. (2002; Figs. 1A, G). Consequently, the identification of our samples as Z. plumula is beyond reasonable doubt. In the experience of the senior author, Z. plumula is usually abundant in eutrophic waters and is accompanied by Z. alrasheidi Ji et al., 2009, which forms a large, leaf-shaped colony with a similar branching pattern. However, the latter species can be distinguished from Z. plumula easily by differences in infraciliature and number of silver lines, its larger zooids (80–120 × 50–60 µm vs. 50–75 × 35–45 µm), and its thick peristomial lip, which has a prominent circumferential infolding (Ji et al. 2009). At first glance, two other marine congeners, Z. alternans Claparède and Lachmann, 1859 and Z. niveum Ehren- berg, 1838, are very similar to Z. plumula in shape of the colony, branching pattern, and presence of macrozooids. However, zooids of both Z. alternans and Z. niveum have different sizes than those of Z. plumula (40–56 × 26–32 µm and 54–66 × 16–22 µm vs. 50–75 × 35–45 µm), and the macrozooids of both species are located on the primary

REDESCRIPTIONS OF FIVE MARINE PERITRICHS Zootaxa 2930 © 2011 Magnolia Press · 49 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. stalk rather than in on the middle or distal parts of secondary branches, as in Z. plumula. In addition, Z. niveum forms a considerably larger colony (>1 cm vs. 3 mm in Z. plumula) (Bauer-Nebelsick et al. 1996; Ji et al. 2006b).

FIGURE 1. Morphology of Zoothamnium plumula from live cells (A–F, J–M), after staining with protargol (H, I, N–P), and after staining with silver nitrate (G, Q) (A, G from Song et al. 2002; B, C after Kahl 1933). A. General view of a typical zooid. B, D–F. Different colony forms. C. Comparison of normal zooid with enlarged zooid. G. Silverline system, arrow marks the trochal band. H. Oral infraciliature, arrow marks the epistomial membrane, double-arrow indicates the distal fragment. I. Detail of infundibular polykineties. J. Branching pattern of a typical colony. K. Variations in shape of zooids. L. Detail of stalk, arrows mark mitochondria. M. Pellicular striations. N. Arrangement of infundibular polykineties. O. Germinal kinety (arrow) and radial myonemes in cell body (arrowheads). P. Epistomial membrane (arrow). Q. General view of silverline system. Abbre- viations: G, germinal kinety; H, haplokinety; P1-3, infundibular polykinety 1–3; Po, polykinety. Scale bars: 30 μm (Fig. A), 100 μm (Fig. K), 400 μm (Figs. F, J).

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TABLE 1. Morphometrical characterizations of five peritrichs. Min—minimum, Max—maximum, Mean—arithmetic mean, SD—standard deviation, n—sample number.

Characters Min Max Mean SD n

Number of silverlines from Z. plumula 50 60 54.5 3.36 11 peristomial lip to trochal Z. nii 47 58 52.1 3.38 15 band Z. wangi 70 85 76.4 4.63 8 P. bidulphiae 25 31 28 2.26 10 P. ma ri n a 25 30 27.5 - 4 Number of silverlines from Z. plumula 22 27 25.3 1.57 10 scopula to trochal band Z. nii 22 30 27.4 3.04 11 Z. wangi 38 50 44.2 4.46 12 P. bidulphiae 91311.61.308 P. ma ri n a 10 15 12 1.79 6

Zoothamnium nii Ji et al., 2005 (Fig. 2; Table 1)

Emended diagnosis. Marine Zoothamnium with colony up to 1 mm high; moderately elongate, median primary stalk giving rise to secondary stalks in regular alternate series in single plane,. Zooids elongate, vase-shaped, measuring 70–80 × 40–50 µm in vivo. Peristomial lip extremely thick, with medial, circumferential infolding in peristomial lip when expanded (“double-layered”). Macronucleus C-shaped, transversely oriented, located in oral half of cell. Pellicular striations indistinct at lower magnifications; 45–60 silverlines lying between peristomial lip and trochal band and 20–30 between trochal band and scopula. P3 consists of three rows that are equal in length and parallel to each other, row 1 slightly separated from rows 2 and 3 for most of length, but all three rows converging adstomally. Redescription. Colony moderately large, up to 1 mm high and containing 30–50 zooids, with broad, diamond- shaped outline. Secondary stalks up to 500 µm long, branching off primary stalk in regular alternate series. Basal secondary stalks longest, with stalks decreasing progressively in length toward tip of colony; secondary stalks branching to form short, dichotomous tertiary branches bearing 2 zooids or single tertiary branches (Figs. 2E, J, K). Stalk with smooth surface and diameter of 12 µm in basal portion of primary stalk, narrowing to 9 µm at distal ends of tertiary stalks. Spasmoneme with diameter of 3.5 µm in primary stalk and 2.5 µm at distal ends of tertiary stalks; band of mitochondria visible as dark granules measuring 0.5 × 0.8 µm, winding along helical path just beneath surface of spasmoneme. Zooids elongate, bell-shaped, measuring 70–80 × 40–50 µm (n=12) (Figs. 2A, I, L, O, P). Body deeply con- stricted below peristomial lip, which is indented by prominent, medial, circumferential infolding (“double-layered”). Maximum width of cell usually at peristomial lip, but occasionally in oral third of body as well; epistomial disc moderately elevated above peristomial lip (Figs. 2A, I, O, P). Pellicular striations easily detectable above × 400 magnification (Figs. 2O, P), but surface of body appears completely smooth at low magnifications (Fig. 2L). Telotroch discoid, measuring 55–65 µm x 40µm (Fig. 2R). Cytoplasm of zooids colorless or slightly gray, filled with tiny (0.5 µm diameter), dense granules and usually containing a few large (5–10 µm in diameter), transparent or gray food vacuoles typically located in center of body (Figs. 2A, L). Single contractile vacuole in adoral position beneath epistomial lip and near dorsal wall of infundibulum. Macronucleus C-shaped, transversely oriented, surrounding micronucleus and lower half of infundibulum (Figs. 2A, M, N). Oral infraciliature as shown in Figures 2B, H, N. Haplo- and polykinety making one and one-quarter circuits around peristome and one additional circuit within infundibulum. Haplokinety and polykinety parallel on peristome, diverging within infundibulum to lie on opposite walls (Fig. 2H). Epistomial membrane short, located at entrance into infundibulum (Fig. 2H, arrow). Germinal kinety running parallel to haplokinety in adoral half of infundibulum (Fig. 2N, arrow). Each of three infundibular polykineties consisting of three rows of kinetosomes. All rows of Pl terminating adstomally at level of cytostome; rows of P2 terminating adstomally at adstomal curvature of P1. Rows of P2 terminating abstomally without merging with P1; abstomal 1/4 of row 3 of P2 diverging

REDESCRIPTIONS OF FIVE MARINE PERITRICHS Zootaxa 2930 © 2011 Magnolia Press · 51 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. from other rows of P2 (Figs. 2 B, H).. All rows of P3 terminating adstomally at point slightly beyond adstomal end of P2 and abstomally at point approximately 1/3 of distance from adstomal to abstomal end of P2. Row 1 of P3 converging with other tow reasons near adstomal end, separated slightly from rows 2 and 3 along remainder of length (Fig. 2B).

FIGURE 2. Morphology of Zoothamnium nii and its synonyms from live cells (A, C–G, I–L, O, P, R), after staining with protargol (B, H, M, N), and after staining with silver nitrate (Q). A. General view of a typical zooid. B. Detail of infundibular polykineties. C, D. Zoothamnium duplicatum, after Kahl (1933). E, J. form of colony. F, G. Zoothamnium sp. after Kahl (1935). H. Oral view of the oral apparatus, arrow marks the epistomial membrane. I, K, L. Variations in shape of zooids. M. Lateral view showing macronucleus (dark area) and micronucleus (arrow). N. Macronucleus (dark area) and germinal kinety (arrow). O, P. Zooids at high magnification showing pellicuilar striations and variations in shape of the body. Q. General view of silverline system. R. Telotroch. Abbreviations: G, germinal kinety; H, haplokinety; P1–3, infundibular polykinety 1–3; Po, polykinety. Scale bars: 40 μm (Figs. A, O, R), 50 μm (Figs. L, P), 300 μm (Figs. D–F, J, K).

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Trochal band consisting of band of dikinetids encircling cell at point 2/3 of distance from peristome to scopula (Fig. 4H, arrows). Silverline system consisting of closely spaced, parallel, transverse silverlines (Fig. 2Q); 45–60 silverlines present between peristome and trochal band, 20–30 between trochal band and scopula. Silverlines near peristome spaced farther apart than those around scopula, and pellicular pores sparsely distributed alongside silverlines (Fig. 2Q). Remarks: In general, zooids of alternately branched species of Zoothamnium such as Z. alternans, Z. niveum and Z. plumula, lack a medial, circumferential infolding on the peristomial lip (“single-layered”), and zooids with an infolding around the peristomial lip (“double-layered”) are more typical of dichotomously branched species such as Z. duplicatum, Z. mucedo, and Z. maximum (Bauer-Nebelsick et al. 1996; Ji & Song 2004; Ji et al. 2005a, 2006b). Therefore, Z. nii has an unusual complex of characters (i.e. the alternately branched stalk and the infolded peristomial lip of the zooid), by which it can be distinguished easily from all the congeners mentioned above. Another species described very recently, Z. alrasheidi Ji et al., 2009, also possesses this set of characteristics during its early development because its zooids have an infolded peristomial lip and its young colonies are alternately branched. However, a colony of Z. alrasheidi in its early stages of development can be distinguished from Z. nii by its larger zooids (80–120 × 50–60 µm vs. 70–80 × 40–50 µm) and a differing pattern of rows in P3 of the infundibular infraciliature (rows 2 and 3 combined into a single band and divergent from row 1 vs. all three rows distinct and parallel) (Ji et al. 2009). Kahl (1933, 1935) reported two populations of Zoothamnium with an infolded peristomial lip as Z. duplicatum (Figs. 2C, D) and Zoothamnium sp. (Figs. 2F, G) respectively. However, both of them had an alternately branched stalk, which is distinctly different from the dichotomous branching pattern characteristic of Z. duplicatum (Kahl 1933; Ji et al. 2005a), but very similar to present species. Accordingly, we suggest that both of these Zoothamnium populations described by Kahl be regarded as synonyms of Z. nii.

Zoothamnium wangi Ji et al., 2005 (Fig. 3; Table 1)

Emended diagnosis. Marine Zoothamnium with colony up to 1 mm high: alternately branched with few (2–4), very long secondary branches . Zooids campanulate to subconical, measuring. 65–90 × 45–55 µm in vivo. Peristo- mial lip thick, without medial, circumferential infolding when expanded. Macronucleus C-shaped, transversely oriented, located in oral half of cell. Pellicular striations closely spaced; 70–85 silverlines lying between peristomial lip and trochal band and 38–50 between trochal band and scopula. P3 consists of two ciliary rows, with row 2 offset slightly toward cytostome relative to row 1. Redescription. Colony moderately large, up to 1 mm high and containing ca. 100 zooids, with broad, fan- shaped outline (Figs. 3E, 4A). Secondary stalks branching alternately from primary stalk, with most basal 2–3 secondary stalks growing to the same length as primary stalk (Figs. 3E, 4A). Cortex of stalk colorless and transparent, with smooth surface and fine longitudinal striations in interior. Diameter of stalk ranging 20 µm in primary stalk to 10 µm in distal branches; spasmoneme measuring 4–10 µm in diameter, containing densely arranged mitochondria (Fig. 3J). Zooids campanulate to subconical, 65–90 µm (n=4) long, widest at peristomial lip, which measures 45–55 µm (n=4) in diameter when fully expanded (Figs. 3A, G). Peristomial lip thick, without secondary circumferential infolding; epistomial disc moderately elevated above peristomial lip (Figs. 3A, G). Pellicular striations closely spaced and not prominent, visible only above × 400 magnification (Fig. 3H); surface of body appearing uniformly smooth at low magnifications. Cytoplasm transparent and slightly grayish, occasionally containing a few gray or yellowish food vacuoles of uneven size (2–10µm) in center of body (Figs. 3A, 4B, C). Single contractile vacuole in adoral position beneath epistomial disc and near dorsal wall of infundibulum. Macronucleus C-shaped, transversely oriented, surrounding micronucleus and lower half of infundibulum (Figs. 3A, I, L). Micronucleus spherical, located adoral to center of macronucleus (Figs. 3A, I, arrow). Oral infraciliature as shown in Figures 3D, E, L, M. Haplo- and polykinety making one and one-quarter circuits around peristome and one additional circuit within infundibulum. Epistomial membrane short, located at entrance into infundibulum (Fig. 3E, arrow). Germinal kinety running parallel to haplokinety in adoral half of

REDESCRIPTIONS OF FIVE MARINE PERITRICHS Zootaxa 2930 © 2011 Magnolia Press · 53 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. infundibulum (Fig. 3L, arrow). Infundibular polykineties 1 and 2 consisting of three rows of kinetosomes each; P3 consisting of two rows. All rows of Pl terminating adstomally at level of cytostome; rows of P2 terminating adstomally at adstomal curvature of P1. Rows of P2 terminating abstomally without merging with P1; abstomal 1/4 of row 3 of P2 diverging from other rows of P2 (Figs. 3D, E). Row 2 of P3 displaced adstomally for short distance relative to row 1 (Fig. 3D). Trochal band consisting of band of dikinetids encircling cell at point 3/4 of distance from peristome to scopula (Fig. 3L, arrowhead). Silverline system consisting of closely spaced, parallel, transverse silverlines, which are spaced relatively wider apart near peristome (Figs. 3B, K); 70–85 silverlines present between peristome and trochal band, 38–50 between trochal band and scopula. Pellicular pores staining faintly, numerous, randomly arranged along silverlines.

FIGURE 3. Morphology of Zoothamnium wangi from live cells (A, C, F–H, J), after staining with protargol (D, E, I, L, M), and after staining with silver nitrate (B, K). A. General view of a typical zooid. B, K. Silverline system, arrow marks the trochal band. C, F. Form of colony. D, M. Detail of infundibular polykineties. E. Oral infraciliature, arrow marks the epistomial membrane. G. Zooids at low magnification showing shape of the body. H. Highly magnified zooid showing pellicular striations. I. Lateral view showing macronucleus (dark area) and micronucleus (arrow). J. Structure of stalk showing densely arranged mitochondria in spasmoneme (arrow). L. Germinal kinety (arrow) and trochal band (arrowhead). Abbreviations: F, filamentous reticulum; G, germinal kinety; H, haplokinety; P1–3, infundibular polykinety 1–3; Po, polykinety. Scale bars: 5 μm (Fig. J), 40 μm (Fig. A), 50 μm (Fig. G), 200 μm (Fig. F), 250 μm (Fig. C).

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Remarks. Zoothamnium wangi is occasionally found in eutrophic marine waters and can be identified easily by the distinctive branching pattern of the colony, shape and size of zooids, number of silverlines, and the pattern of kinetosome rows in P3. Zoothamnium plumula, Z. commune, Z. alternans, and Z. xuianum resemble Z. wangi in having an alternately branched stalk and a relatively thin peristomial lip without a medial circumferential infolding. In the present study, it was observed that young colonies of Z. plumula very much resemble mature colonies of Z. wangi in outline as well as shape and size of zooids and, therefore, cannot be distinguished from the latter by characters visible in the living organisms. However, the two species can be distinguished easily in preparations stained with silver nitrate or protargol by the total number of silverlines (108–135 in Z. wangi vs. 72–87 in Z. plumula) and the number of ciliary rows in P3 (2 in Z. wangi vs. 3 in Z. plumula).

FIGURE 4. Morphology of Pseudovorticella bidulphiae (A–D, H–M) and similar species (E–G). A, I. General view of a typical cell. B. Variations in shape of the cell body. C, D. After Stiller (1939). E. Pseudovorticella pseudocampanula (after Foissner 1979). F. Pseudovorticella sauwaldensis (from Foissner and Schiffmann, 1979). G. Vorticella venusta (from Warren 1986). H. Oral infraciliature, arrow marks the epistomial membrane. J. Pellicular striations. K. Detail of stalk. L. Protargol-stained specimen showing infundibular polykineties. M. General view of silverline system, arrows mark the trochal band. Abbreviations: G, germinal kinety; H, plokinety; P1–3, infundibular polykinety 1–3; Po, polykinety. Scale bars: 20 μm (Figs. A, E–G), 50 μm (Figs. C, I).

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FIGURE 5. Morphology of Pseudovorticella marina (A–D, I–Q) and similar species (E–H). A, J, M. General view of typical cells. B. Variations in shape of the cell body. C. From Warren, 1986. D. Oral infraciliature, arrow marks the epistomial membrane. E. Pseudovorticella punctata (from Ji et al. 2006a). F. Vorticella campanulata (from Warren 1986). G. Vorticella fusca (from Warren 1986). H. Vorticella jaerae (from Precht 1935). I. Zooids seen at low magnification. K. Detail of stalk, arrows mark mitochondria. L. Detail of infundibular polykineties. N. Trochal band (arrows). O. Oral view of protargol impregnated specimen showing the epistomial membrane (arrow) and germinal kinety (arrowheads). P, Q. Silverline system, arrows mark pellicular pores. Abbreviations: G, germinal kinety; H, haplokinety; P1–3, infundibular polykinety 1–3; Po, polykinety. Scale bars: 20 μm (Figs. A–C, E–H), 60 μm (Fig. J), 100 μm (Fig. M), 150 μm (Fig. I).Fig. 1

Zoothamnium commune resembles Z. wangi in most living characters. However, Z. wangi has more silverlines from the peristomial lip to the trochal band (70–85 vs. 59–70) and a different number of kinetosome rows in P3 (2 in Z. wangi vs. 3 in Z. commune) (Ji et al. 2006b). Zoothamnium alternans has large macrozooids that form acetab-

56 · Zootaxa 2930 © 2011 Magnolia Press JI ET AL. TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. uliform telotrochs on the primary stalk, which are lacking in Z. wangi, plus its microzooids are considerably smaller than zooids of Z. wangi (40–56 × 26–32 µm vs. 65–90 × 45–55 µm) (Ji et al. 2006b). Zoothamnium xuianum has also much smaller zooid size than that of Z. wangi (30–50 × 20–40 µm vs. 65–90 × 45–55 µm), thus it can be well distinguished from the latter (Sun et al. 2005) Living colonies of two other congeners, Z. thiophilum Stiller, 1946 and Z. hentscheli Kahl, 1935, also resemble Z. wangi, and their infraciliatures and silverline systems remain unknown, preventing a comparison with those of Z. wangi. However, both of these species are freshwater forms (Kahl 1935; Stiller 1946) and Z. wangi seems to be found exclusively in marine habitats.

Pseudovorticella bidulphiae (Stiller, 1939) Ji, Sun, Song & Warren, 2009 (Fig. 4; Table 1)

Pseudovorticella bidulphiae is characterized by the following characteristics: cell body measuring 30–40 × 35–40 µm (n=4) in vivo, two ventrally located contractile vacuoles, J-shaped macronucleus, 24–28 silverlines lying between peristome and trochal band, 9–11 silverlines lying between trochal band and scopula, P3 composed of only two ciliary rows with row 1 noticeably shorter than row 2 at its adstomal end (Song et al. 2009). Here, we sup- ply its illustrations of morphology (Fig. 4) and a brief comparison with related species: At low magnifications, Pseudovorticella pseudocampanula Foissner, 1979 (Fig. 4E), P. sauwaldensis Foissner & Schiffmann, 1979 (Fig. 4F) and Vorticella venusta Nenninger, 1948 (Fig. 4G) resemble P. bidulphiae in shape and size of the cell body. However, all three of these species live in fresh water (vs. marine habitat in P. bidulphiae) and a single contractile vacuole (vs. 2 in P. bidulphiae) (Foissner 1979; Foissner & Schiffmann 1979).

Pseudovorticella marina (Greeff, 1870) Ji, Sun, Song & Warren, 2009 (Fig. 5; Table 1)

Pseudovorticella marina is characterized by the following characteristics: cell body measuring 40–50 × 35–45 µm (n=8) in vivo, macronucleus J-shaped, single contractile vacuole located near ventral wall of infundibulum, 25–30 transverse silverlines lying between peristome and trochal band, 10–15 silverlines lying between trochal band and scopula, P3 composed of three ciliary rows, rows 1 and 2 shorter than row 3 at adstomal ends (Song et al. 2009). Illustrations of its morphology (Fig. 5) and brief comparison with similar species are also presented here. The congener that most closely resembles P. marina is P. punctata (Dons, 1918) Warren, 1987 (Fig. 5E), which has similar body shape and size, but can be separated by its tuberculate pellicle (vs. smooth in P. marina) and P3 consisting of two rows (vs. 3 rows in P. m a r in a) (Ji et al. 2006a). Living cells of,three species of Vorticella, V. campanulata (Kahl, 1933) Šramek-Hušek, 1948 (Fig. 5F), V. fus ca Precht, 1935 (Fig. 5G) and V. ja e r a e Precht, 1935 (Fig. 5H), also bear some resemblance to P. marina at low magnification. Vorticella campanulata and P. m ar i na have similar numbers of silverlines, but the former is a freshwater species (vs. marine in P. m a r in a ). Vorticella fusca has larger body than P. marina (80–110 × 65–75 µm vs. 40–50 × 35–45 µm), and zooids of V. ja e r ae do not have the elongate and twisted macronucleus and strongly everted peristomial lip characteristic of P. marina (Warren 1986).

Acknowledgements

This work was supported by the Natural Science Foundation of China (project number: 30700066), BK Program of Korea and the Research Group Project (No. RGP-VPP-083), King Saud University Deanship of Scientific Research.

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