Parallelostrombidium ellipticum, Liu & Yi & Lin & Li & Al-Farraj & Al-Rasheid & Song, 2015
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publication ID |
https://doi.org/ 10.1111/zoj.12257 |
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persistent identifier |
https://treatment.plazi.org/id/18298784-FFFA-9E7A-8F56-F9D9FBC807C6 |
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treatment provided by |
Felipe |
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scientific name |
Parallelostrombidium ellipticum |
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sp. nov. |
PARALLELOSTROMBIDIUM ELLIPTICUM SP. NOV.
( FIG. 2 View Figure 2 , TABLE 1)
Diagnosis: Body shape elliptical, anterior end transversely truncated with conspicuous apical protrusion, size ∼60 × 40 μm in vivo; macronucleus ellipsoidal; usually ∼19 anterior, ∼11 ventral, and invariably two long thigmotactic membranelles; girdle kinety comprising ∼70 dikinetids, spiralling around the cell with one and a half whorls, with the anterior end extending slightly to the left of the ventral kinety; ventral kinety with ∼26 dikinetids; the posterior portions of girdle and ventral kineties crossing the right margin of the cell with their ends intersecting each other. Brackish water form.
Type locality: A shrimp-culturing pond near Guangzhou (22°40′N, 113°40′E), Guangdong, China. Water temperature was 25.8 °C, salinity 1.7‰, and pH 8.9 GoogleMaps .
Etymology: The Latin adjective ellipticum [neuter gender] (elliptical) refers to the elliptical body shape of the species.
Deposition of slides: A protargol slide containing the holotype specimen (marked with a black circle) has been deposited at the Natural History Museum, London, with registration number NHMUK 2014.5 View Materials .7.2. Two protargol slides with paratype specimens have been deposited in the Laboratory of Protozoology, Ocean University of China, with registration numbers LWW 09041401 -1 and LWW 09041401 -2 .
Deposition of SSU rRNA gene sequence data: The SSU rRNA gene sequence has been deposited in GenBank with accession number KJ704987 View Materials . Its length and G + C content are 1771 bp and 46.6 mol %, respectively.
Description: Cell shape elliptical or oval, in vivo 50– 70 × 30–45 μm, length: width ratio about 1.5–2: 1 in vivo ( Fig. 2A, B, F, J–L View Figure 2 ). Cells slightly swollen after protargol impregnation, size about 56–73 × 35–48 μm, distend- ed cell surface not recognizable. Anterior end transversely truncated, collar region domed to form a conspicuous apical protrusion about 4 μm high in vivo, which shrank after protargol impregnation ( Fig. 2A, F, J, N View Figure 2 , arrow). Posterior end narrowly rounded and slanted slightly to the right ( Fig. 2A, J View Figure 2 ). Cell surface bulged in anterior third of right lateral and half of left lateral margins, which renders cell bilaterally asymmetrical ( Fig. 2A, B, J, L View Figure 2 ). Cell dorsoventrally flattened with a thickness: width ratio of about 3:4 ( Fig. 2Q View Figure 2 ).
Hemitheca, composed of polygonal platelets about 2 μm across in vivo, covering the posterior part of the cell below the girdle kinety ( Fig. 2C, P View Figure 2 ). Cytoplasm colourless, often filled with lipid droplets 2–4 μm across and food vacuoles 7 μm across, containing some ingested yellow algae ( Fig. 2A, B, K View Figure 2 ). Extrusomes prominent and acicular shaped ( Fig. 2D View Figure 2 ), about 9 × 0.5 μm in vivo, attached to cortex in a shallow bulge above the girdle kinety ( Fig. 2O, R View Figure 2 ). Extrusome attachment sites evenly spaced in three rows, forming a stripe surrounding the body ( Fig. 2A, O, R View Figure 2 ). Macronucleus in the centre of the cell, ellipsoidal to ovoidal ( Fig. 2I, V View Figure 2 ), containing numerous nucleoli 0.5–2 μm across. Contractile vacuole, cytopyge, and micronucleus not recognized. In Petri dish with in situ water at room temperature, cells crawling over debris using their two thigmotactic membranelles or rotating about the main cell axis in spirals (about 50 μm across) with the anterior membranellar cilia spreading radially ( Fig. 2E View Figure 2 ).
Buccal cavity narrowed and deep, extending obliquely to the right and occupying two fifths of cell length ( Fig. 2A, H, K View Figure 2 ). Adoral zone of membranelles composed of anterior, ventral, and thigmotactic membranelles ( Fig. 2H, W View Figure 2 ), each of which consist of three parallel rows of kinetosomes, except for the two posterior-most ventral membranelles, which probably comprise only two rows. Anterior membranellar zone composed of 18–22 membranelles with cilia up to 15–17 μm long in vivo, stretching laterally or even slightly posteriorly when swimming ( Fig. 2A, B, L, N View Figure 2 ). Bases of the anterior membranelles about 8 μm long. Ventral membranellar zone composed of nine to 13 membranelles, cilia 5–9 μm long in vivo, bases decreasing in length towards the cytostome and 3–5 μm long ( Fig. 2A, H View Figure 2 ). Two thigmotactic membranelles pointing distinctly posteriorly in vivo owing to their much longer cilia, which are about 30 μm in length in both ( Fig. 2A, M, Q View Figure 2 , arrows). Bases of the thigmotactic membranelles about 10 μm long with their outside parts curving downwards ( Fig. 2H, W View Figure 2 ). Endoral membrane located on the inner wall of the buccal cavity, about 20 μm long, extending to the centre of the apical protrusion and probably composed of a single row of kinetosomes ( Fig. 2H, S View Figure 2 ); no cilia observed. Pharyngeal fibres not observed.
Somatic cilia positioned in shallow furrows on the body and arranged in a girdle and a ventral kinety. Girdle kinety consisting of 57–80 dikinetids; within each dikinetid, the left basal body bears a short cilium about 2 μm long in vivo whereas the right one is associated with a conspicuous argentophilic fibre (about 1 μm long; Fig. 2H, T View Figure 2 ). The girdle kinety starting about 40% back from anterior cell end and below the ventral membranelles, with about one to three dikinetids to the left of the ventral kinety, running anteriad slightly across right ventral, extending obliquely posteriad across dorsal and left half of ventral side, then crossing the posterior-right margin in posterior sixth of cell and terminating under the ventral kinety in the posterior dorsal area ( Fig. 2G–I, U, V View Figure 2 ). The girdle kinety, therefore, spirals approximately one and a half whorls around the cell. Ventral kinety composed of 20–30 densely arranged dikinetids, and each dikinetid bearing a short cilium, about 2 μm long in vivo, associated with the anterior basal body and an argentophilic fibre, about 1 μm long, associated with the posterior one ( Fig. 2H, I View Figure 2 ). Ventral kinety commencing below the anterior end of the girdle kinety, extending posteriad on the right ventral side, crossing the right margin to the dorsal side. The posterior portion of ventral kinety extending posteriad obliquely on the dorsal side and finally intersecting with the posterior end of girdle kinety ( Fig. 2G, H, U, Y View Figure 2 ).
An early divider was observed. The oral primordium occurred on the left of the anterior end of the girdle kinety and below the thigmotactic membranelles, where a cuneate, longitudinally orientated, field of basal bodies developed ( Fig. 2X View Figure 2 , arrow).
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