Cyrtohymena seorakensis Omar & Jung 2020, sp. n.
Creators: name: Omar, Atef
name: Jung, Jae-Ho
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Protozoa
Ciliophora
Hypotrichea
Oxytrichida
Oxytrichidae
Cyrtohymena
Cyrtohymena seorakensis

description: Cyrtohymena seorakensis sp. n.
(Figs. 1–5; Table 1)
urn:lsid:zoobank.org:act: 0F24868A-99CC-4F0C-9F83-139BC5482E9C
Diagnosis. Size in vivo 100–150 × 25–35 μm; body slenderly ellipsoid with posterior end narrower than anterior; cytoplasm colorless, cell appear brownish under low magnification due to many crystals. Contractile vacuole at left margin of mid-body, with two inconspicuous collecting canals. Cortical granules spherical, randomly scattered, yellowish, and 0.5–0.8 μm across. Two macronuclear nodules with 2 or 3 micronuclei. Adoral zone occupies about 32% of body length, consists of an average of 28 membranelles. 17 frontal-ventral-transverse cirri of which only four transverse cirri. 13–19 right and 17–21 left marginal cirri. Six dorsal kineties of which kinety 4 commences posterior to mid-body and kineties 5 and 6 are dorsomarginal.
Zoobank registration of Cyrtohymena seorakensis sp. n.: urn:lsid:zoobank.org:act: 0F24868A-99CC-4F0C- 9F83-139BC5482E9C
Type locality. Terrestrial moss from Seorak Mountain, South Korea (N38° 11′ 7″, E128° 28′ 39″).
Type material. The holotype (NIBRPR 0000110249) and two paratype slides (NIBRPR 0000110219 and NI- BRPR 0000110220) with protargol-impregnated specimens have been deposited in the National Institute of Biological Resources (NIBR), South Korea. Ten other paratype slides with protargol-impregnated specimens have been kept in our laboratory.
Etymology. Named after the Mountain in which it was discovered.
Morphological description. Size in vivo 100–150 × 25–35 μm; on average 97 × 27 μm after protargol prepa- rations (Table 1). Body flexible and slightly contractile; ellipsoid with both ends rounded, posterior end distinctly narrower than anterior, right margin usually slightly concave, left slightly convex; ventral surface flat to slightly convex, dorsal surface distinctly convex (Figs 1A, C, 2A, B, F, G, H). Nuclear apparatus left of midline, in middle half of cell, composed of two ellipsoid macronuclear nodules separated with 2–14 μm wide distance in protargol preparations, and 2 or 3 globular micronuclei near or attached to macronuclear nodules (Figs 1A, E, 2F, G). Contractile vacuole at left margin of mid-body, with two inconspicuous collecting canals (Figs 1A, 2A). Cortical granules yellowish, randomly scattered, and 0.5–0.8 μm across (Figs 1C, 2C, D). Cytoplasm colorless, contains few to many 1–3 μm across lipid droplets, up to 10 μm-sized food vacuoles with fungi, starch grains, and algae, and few to many crystals making cells appear brownish under low magnification (Figs 1A, 2 A–D). Usually crawls slowly forward and backward on bottom of Petri dish culture, rarely swims.
Adoral zone of membranelles (AZM) occupies about 32% of body length and composed of 28 membranelles on average, cilia up to 18 μm long in vivo and about 14 μm in SEM preparations (Figs 1A, D, 2 F–I). Undulating membranes in typical Cyrtohymena pattern; paroral membrane commences at about 7.5% of body length and about 1 or 2 μm ahead of endoral, paroral cilia about 8 μm in SEM preparations, attached to each other and covering buc- cal cavity; pharyngeal fibers extend to mid-body (Figs 1D, 2 F–I).
Cirral pattern oxytrichid, invariably 17 frontal-ventral-transverse cirri in ~50 morphostatic specimens studied (the opisthe of a single late divider specimen observed with only 14 cirri). Three slightly enlarged frontal cirri about 15 μm in SEM preparations, right cirrus posterior to distal-most adoral membranelle, middle cirrus anterior to buc- cal cirrus, left cirrus anterior to curved paroral membrane. One buccal cirrus right to middle portion of undulating membranes. Invariably four frontoventral cirri in two oblique pairs (V-shaped); anterior pair right of the buccal cirrus and in line with right marginal row; posterior pair slightly anterior and left to right marginal row. Three postoral cirri in anterior half of cell, cirri IV/2 and V/4 close to buccal vertex, distance between V/4 and V/3 about 8 μm on average. Two obliquely arranged pretransverse cirri, with cilia about 13 μm in SEM preparations. Invariably four, slightly thickened, transverse cirri at posterior cell end about 18 μm in vivo. Right marginal cirral row composed of about 16 cirri, commences at about 22% of body length and ends at level of first pretransverse cirrus. Left marginal cirral row composed of an average of 19 cirri, commences left of posterior portion of AZM at about 27% of body length and curved posteriorly to right of cell midline at posterior cell margin (Figs 1A, D, E, 2 F–J; Table 1).
Six dorsal kineties (DK) including two dorsomarginal kineties (DK5 and DK6) composed of a total of 62 bristles on average, kinety 1 slightly shortened anteriorly, kineties 2 and 3 bipolar, kinety 3 fragmented posteriorly, kinety 4 begins posterior to mid-body, kinety 5 ends posterior to mid-body, kinety 6 ends in anterior third of body and composed of 3–6 dikinetids. Dorsal bristles 3–4 μm long on average in vivo. Three caudal cirri slightly right of cell’s midline at end of kineties 1, 2, and 4, about 12 μm in SEM preparations (Figs 1E, 2G; Table 1).
Resting cyst. Cysts in vivo spherical, 18–20 μm in diameter. Cyst wall about 1 μm thick, structureless in light microscope. Macronuclear nodules fused to a central mass. Cytoplasm hyaline packed with minute lipid droplets up to 2 μm across (Fig. 1B, 2E).
Notes on ontogenesis. Only three cells in the middle and late stages of division were observed. The postoral cirrus V/3 was not observed during the late division stages indicating that it was involved in the primordia formation as in other Cyrtohymena species (Singh & Kamra 2015; Voss 1991) (Figs 3A, C, E, 4 A–C). The dorsal morphogenesis is of typical Oxytricha -pattern, that is, parental kineties develop intrakinetally to form kineties 1–3 in both the proter and opisthe. Kinety 3 fragments posteriorly and forms fourth anlage (kinety 4). The parental kineties 4–6 dedifferentiate, and the new kineties 5 and 6 develop de novo on the right side of the cells as dorsomarginal kineties. The three caudal cirri are formed at the posterior end of kineties 1, 2, and 4 of both the proter and opisthe (Figs 3B, D, F, 4D).
Phylogeny. The SSU rDNA sequence of Cyrtohymena seorakensis sp. n. is 1,539 base pairs long and has a GC content of 45.44% and available under GenBank accession number MT103333. Cyrtohymena seorakensis sp. n. shows a similarity of 99.9% (one nt difference) with the Indian population of C. citrina and cluster together in the phylogenetic trees (Fig. 5). This clade is a sister to a clade containing C. muscorum, which shows 99.6% similarity with C. seorakensis sp. n., and two urosomoidid species. The Namibian population of C. citrina nests at the base of the clade containing these three Cyrtohymena sequences and shows a similarity of 99.3% (10 nt difference) to C. seorakensis sp. n. The other two sequences of C. citrina are identical to each other (possibly from the same population) and almost identical (0.1% dissimilarity = 1 nt difference) to Australocirrus shii. They cluster together with three neokeronopsid species distant from other Cyrtohymena species.
description: Published as part of Omar, Atef & Jung, Jae-Ho, 2020, Morphology and Molecular Phylogeny of the Soil Ciliate Cyrtohymena seorakensis sp. n. (Ciliophora, Hypotricha, Oxytrichidae), pp. 561-572 in Zootaxa 4758 (3) on pages 562-564, DOI: 10.11646/zootaxa.4758.3.8, http://zenodo.org/record/3734771