Pleuronema grolierei Wang et al., 2008

Pan, Xuming, Huang, Jie, Fan, Xinpeng, Ma, Honggang, Al-Rasheid, Khaled A. S., Miao, Miao & Gao, Feng, 2015, Morphology and Phylogeny of Four Marine Scuticociliates (Protista, Ciliophora), with Descriptions of Two New Species: Pleuronema elegans spec. nov. and Uronema orientalis spec. nov., Acta Protozoologica 54 (1), pp. 31-43 : 38

Pleuronema grolierei Wang et al., 2008 ( Figs 3A–H ; Table 1 )

Pleuronema grolierei was originally described by Wang et al. (2008b), but the molecular information of this form was absent in his study. Based on the current study, an improved diagnosis of this species is provided, with new characters and SSU rRNA gene sequence data.

Improved diagnosis: Size in vivo 60–80 × 20–40 µm with an oval to elliptical body shape; buccal field occupying two-thirds of body length; single contractile vacuole located slightly ventrally in the posterior fourth; ten to fifteen prolonged caudal cilia in posterior half of body; cilia in PM uniquely short and inconspicuous; one preoral and 18 to 32 somatic kineties; all membranelles consisting of two rows of basal bodies; the posterior end of the anterior fragment of M2a straight; M2a about twice as long as M3; PM about two-thirds of cell length; single spherical macronucleus and marine habitat.

Description of the Qingdao population: In vivo about 60–70 × 25–35 µm, elongate oval to elliptical in outline, both ends broadly rounded ( Fig. 3A ). Buccal field large with shallow buccal cavity, occupying about two-thirds of body length and almost one-third of body width ( Fig. 3A ). Cilia in both PM and membranelles obviously short (about 20 µm long) ( Fig. 3B ). Pellicle rigid and slightly notched with extrusomes about 3 µm long, closely arranged beneath. Cytoplasm colourless to slightly grayish, packed with many shining globules of varying size, food vacuoles which are usually large and filled with indefinable contents ( Fig. 3D ). Single spherical macronucleus, about 15 µm in diameter ( Fig. 3H ). Contractile vacuole about 20 µm in diameter, located slightly ventrally in posterior quarter of the cell ( Fig. 3A ). Somatic cilia usually about 10 µm long; about ten caudal cilia, approximately 20 µm long ( Fig. 3C ). Movement moderately fast, rotating about main body axis, somewhat drifting and wobbling and then motionless for short periods.

Eighteen to 22 somatic kineties, extending over the entire length of the cell and terminating at the apical end around a large glabrous apical plate. All kineties composed of dikinetids in anterior half of the body and monokinetids in posterior half. One preoral kinety to the left of the buccal field. Oral apparatus as shown in

Figs 3E–G; the anterior M1 about the same length as M3; M2a double-rowed with its posterior end straight (Figs 3E, G). All the membranelles composed of two longitudinal rows of basal bodies. PM about two-thirds of cell length with its posterior end strongly curved around the posterior margin of buccal area.

SSU rRNA gene sequence: The SSU rRNA gene sequence of Pleuronema grolierei Wang et al., 2008 has been deposited in the GenBank database with the accession number, length and G+C content as follows: KF840519 , 1738 bp, 43.44%.

Comparison and remarks: Our population is very similar to previous populations ( Wang et al. 2008a) in both living and infraciliature data, except for minor differences in the number of somatic kineties (18–22 in the present study vs. 24–32) and the number of caudal cilia (ten in the present population vs. 15). Consequently, these two forms are conspecific.

Figures

Fig. 3.Pleuronema grolierei Wang et al., 2008 (A–H) andP. setigerum Calkins, 1902 (I–M) in vivo (A–D, I–K) and after protargol (E–H, L, M). A, I – ventral views of typical individuals, arrow in (A) shows contractile vacuole, arrowheads in (I) mark paroral membrane; B – ventral view, arrowheads mark oral cilia; C, K – ventral views, arrowheads point to caudal cilia; D – ventral view, arrow marks ingested algae, arrowhead shows irregularly-shaped crystals; E – anterior region, arrow shows the anterior part of membranelle 2; F – detailed structure of the buccal area; G – posterior region, arrowhead points to membranelle 3; H – macronucleus; J – ventral view, arrowheads show irregularly-shaped crystals; L – posterior region, arrowhead indicates the ring-like posterior end of M2a; M – detailed structure of the buccal area, arrow marks membranelle 3, arrowheads show preoral kineties. M1 – membranelle 1; M2a – the anterior part of membranelle 2; M2b – the posterior part of membranelle 2; Ma – macronucleus. Scale bars: A, I = 20 μm, M = 5 μm.