Pseudocyrtohymenides lacunae, Jung & Park & Min, 2017

Jung, Jae Ho, Park, Kyung Min & Min, Gi Sik, 2017, Morphology and Molecular Phylogeny of Pseudocyrtohymenides lacunae nov. gen., nov. spec. (Ciliophora: Oxytrichidae) from South Korea, Acta Protozoologica 56 (1), pp. 9-16 : 10-12

Pseudocyrtohymenides lacunae nov. spec.

Diagnosis: Size in vivo 120–165 μm × 25–50 μm; body flexible and slightly contractile, slender to el- lipsoidal in shape, grayish to slightly yellowish under low magnification; two macronuclear nodules with ap- proximately two micronuclei; contractile vacuole at left mid-body; cortical granules spherical, yellowish, approximately 1 μm in diameter, irregularly distributed on cortex; on average, 37 adoral membranelles, 18 FVT cirri, and 23 left and 27 right marginal cirri; undulating membranes in Australocirrus – Cyrtohymena pattern; four or five dorsal kineties composed of three dorsal and one or two dorsomarginal rows ( Urosomoida pattern); dorsal kinety 3 non-fragmented; caudal cirri absent.

Type locality: Songjiho lagoon (38°20'09" N, 128°30'57" E), South Korea near the East Sea ; salinity of 5.3 psu .

Type materials: The holotype ( NIBRPR0000104 263 ) and three paratype ( NIBRPR0000104264 – NIBR PR0000104266 ) slides with protargol-impregnated specimens were deposited in the National Institute of Biological Resources ( NIBR), South Korea. The other three paratype slides ( MABIK PR00042645–00042647 ) have been deposited in the National Marine Biodiversity Institute of Korea ( MABIK), South Korea. The holotype and other relevant specimens were marked using circles on the bottoms of the slides.

Etymology: The species-group name “ lacunae ” is derived from the Latin noun lacuna (lagoon) in the singular genitive case, denoting where the specimens were discovered.

Description: Size in vivo 120–165 μm × 25–50 μm (~ 3.2:1, n = 5; Figs 1A ; 2A–D ), on average 105.1 μm × 36.6 μm in protargol preparations ( Table 1 ; Figs 1C, D ; 2F, G ). Body flexible and slightly contractile; cell colour grayish to slightly yellowish under low magnification. Invariably two macronuclear nodules, el- liptical to elongated oval, 14.0–19.5 μm × 4.5–8.5 μm (stained); one to four micronuclei, spherical, 1.5–3.0 μm × 1.0–2.5 μm (stained). Contractile vacuole on left side of mid-body, approximately 10 μm in diameter without conspicuous collecting canals ( Figs 1A ; 2A ). Cortical granules irregularly distributed on cortex, yellowish, spherical, approximately 1 μm in diameter ( Figs 1B ; 2C, E ). Cell inclusions with food vacuoles (bacteria, small protists) and granular inclusions. Crawling moderately fast on bottom of Petri dish.

All cirri relatively fine, mostly 12–21 μm long in vivo; frontal and transverse cirri 18–21 μm long; other cirri 12 μm long ( Figs 1A ; 2D, G ). Arrangement of FVT cirri as in other flexible 18-cirri hypotrichs; usually three frontal, four frontoventral, one buccal, five ven- tral, and five transverse cirri. A few cells show variation in the number of cirri, ranging from 16 to 23; frontal, frontoventral, buccal cirri invariably eight; ventral and transverse cirri 5–9 and 3–6 cirri, respectively; transverse cirri obliquely arranged, slightly J-shaped. One left and one right marginal row, composed of 19–27 cirri and 23–33 cirri, respectively; both posterior ends never connected, terminate at similar level. Usually five dorsal kineties, that is constantly three bipolar kineties and usually two (20 of 21 specimens analysed) dorsomarginal kineties; dorsal kinety 4 posteriorly slightly shortened (12–19 bristles); kinety 5 conspicuously posteriorly shortened, if present, composed of 1–3 bristles ( Figs 1D ; 2F ); dorsal kinety 3 non-fragmented; dorsal cilia approximately 2.5–3.0 μm long ( Fig. 2E ). Caudal cirri absent.

Adoral zone of membranelles approximately 38% of body length in impregnated specimens; base of the largest membranelles approximately 5 μm long; cilia of membranelles approximately 13 μm long. Paroral and endoral membrane in Australocirrus – Cyrtohymena pattern, namely, anterior part of paroral membrane distinctly curved in leftward direction and recurved slightly distally; undulating membranes intersect in mid-buccal cavity ( Figs 1C, E ; 2H ).

Phylogenetic analyses: The SSU rDNA sequence of Pseudocyrtohymenides lacunae was 1,576 bp in length (GenBank accession number: MF319121 ). The sequence similarity between Pseudocyrtohymena koreana and Pseudocyrtohymenides lacunae was 99.4% (10 nt difference). In the phylogenetic tree ( Fig. 3 ), although Pseudocyrtohymenides nov. gen. clustered with the genus Pseudocyrtohymena , the supporting values were not significant (posterior probability of 0.52, boot- strap value of <50%). The clade Pseudocyrtohymena – Pseudocyrtohymenides showed a sister relationship with Pseudogastrostyla flava – Rubrioxytricha haematoplasma – R. ferruginea – Ponturostyla enigmatica (posterior probability of 0.85, bootstrap value of <50%). In addition, the clade Pseudocyrtohymena – Pseudocyrtohymenides did not cluster with Cyrtohymena species.

Figures

Fig. 1. Pseudocyrtohymenides lacunae nov. gen., nov. spec. (A, B), living specimens and (C–E), after protargol impregnation. (A, B), ventral (A) and dorsal (B) views of representative specimens; arrow denotes contractile vacuole. (C, D), ventral (C) and dorsal (D) views of the holotype specimen. (E), ventral views showing the variation of frontal-ventral-transverse cirri. AZM, adoral zone of membranelles; DK1, dorsal kinety 1; EM, endoral membrane; G, cortical granules; LMR, left marginal cirral row; Ma, macronuclear nodules; Mi, micronuclei; PM, paroral membrane; RMR, right marginal cirral row; TC, transverse cirri. Scale bars: 50 µm.

Fig. 2. Pseudocyrtohymenides lacunae nov. gen., nov. spec. (A–E), living specimens; (F–K), after protargol impregnation. (A, D), ventral views of representative specimens. (B, C, E), dorsal views showing cortical granules and dorsal bristles. (F–K), dorsal (F, J) and ventral (G–I, K) views showing infraciliature and nuclear apparatus. AZM, adoral zone of membranelles; CV, contractile vacuole; DB, dorsal bristle; DK1–4, dorsal kineties 1–4; EM, endoral membrane; FC, frontal cirrus; G, cortical granules; LMR, left marginal cirral row; Ma, macronuclear nodules; Mi, micronuclei; PM, paroral membrane; RMR, right marginal cirral row; TC, transverse cirri; VC, ventral cirri. Scale bars: 100 µm in A–D and 50 µm in F–G.

Fig. 3. Phylogenetic tree of SSU rRNA gene sequences, showing the position of Pseudocyrtohymenides lacunae nov. spec. on the basis of Maximum Likelihood (ML) and Bayesian Inference (BI). Bootstrap values of ML and posterior probabilities of BI were denoted on each interior branch. If the values of the bootstrap and the posterior probability were less than 50% and 0.50, respectively, they were excluded. The scale bar represents one nucleotide substitution per 100 nt.