Diatoma sinensis Bing Liu & Rioual, sp. nov.

Yuan, Li, Liu, Bing, Rioual, Patrick, Long, Ji-Yan & Peng, Yu-Mei, 2022, Diatoma sinensis: a new diatom species (Bacillariophyta) found in the brackish Lake Qinghai, China, PhytoKeys 210, pp. 93-108 : 93

Diatoma sinensis Bing Liu & Rioual, sp. nov.

Figs 2 , 3 , 4 , 5 , 6 , 7

Holotype.

JIU! G202201, specimen circled on slide, illustrated as Fig. 2B .

Registration.

Phycobank http://phycobank.org/103359.

Type locality.

China. Qinghai Province: Lake Qinghai, a sampling point near the lakeshore (Fig. 1 , sampling site 1), 36°50'34"N, 99°42'39"E, 3210 m a.s.l., collected by Bing Liu, July 19, 2019.

Description.

LM (Fig. 2 ). Living cells always observed in girdle view are rectangular (Fig. 2A , arrows). Cell depth (along the pervalvar axis, n = 35) 3.3-8.8 μm, always larger than valve width (2.0-3.0 μm). Valve linear-lanceolate, with subcapitate to capitate apices (Fig. 2B-R ). Valve dimensions (n = 69): 24-88 μm long, 2.0-3.0 μm wide, transapical ribs unevenly spaced, 8-13 in 10 μm. Striae and sternum not resolved under LM.

SEM (Figs 3 - 7 ). Frustule and valvocopula view: Frustule rectangular in girdle view (Fig. 3A ); normal vegetative frustule composed of epivalve, hypovalve, and six girdle bands (Fig. 3B-D ). Four girdle bands associated with the epivalve (Fig. 3B-D, B1 to B4), two with hypovalve (Fig. 3B-D, B5 and B6 ), yielding in a 4:2 configuration of girdle bands in non-dividing vegetative cells. Girdle bands open and having a closed-open-closed-open-closed-open arrangement at one apex in a complete cell (Fig. 3C-D ). Striae continuing onto deep mantle and no blisters present (Fig. 3B-D ). Valvocopula open at one pole, always furnished with two rows of poroids, but sometimes with very short isolated third row of poroids (Fig. 4D , arrow). Valvocopula forming an open ring with the same shape as the valve outline, closely attached to the mantle interior, surrounding the valve margin (Fig. 4B ). Advalvar row of valvocopula poroids of each valvocopula bisecting pars interior from exterior, located at mid-line, pars media (Fig. 3C-D ), inner row of poroids and the very short isolated third row located on pars exterior (Figs 4D , 5C-E ). Valvocopula with crenulated edge attaching to valve, internally visible over virgae (Fig. 4G-H , arrows). Valvocopula open ends hyaline (with no ornamentation) (Figs 4H , 5C , 5F ). Poroid density of the valvocopula is 66-70 in 10 μm.

External view: Valve linear-lanceolate, with subcapitate to capitate apices (Fig. 6A-B ). Valve surface smooth, spines absent. Striae uniseriate, perpendicular to a narrow central sternum, 43-54 in 10 μm. Striae in groups of two to six separated by transverse ribs continuing down the vertical mantle (Figs 3A-D , 6C-H ). More closely spaced rows of pores occurring at both apices, forming rather distinct apical pore fields (Fig. 6C, E, F, H ). Two rimoportulae per valve, one per pole, with slit-like opening externally (Fig. 6C, E, F, H ).

Internal view: Valve linear-lanceolate, with subcapitate to capitate apices (Fig. 7A-B ). Transapical ribs, mostly primary, part of internal valve surface (Fig. 7A-H ). Rimoportula prominent, two per valve (n = 22), present at both apices, possessing bilabiate structure (Fig. 7C, E, F, H ). Rimoportula positions variable, either embedded in a transapical rib (Fig. 7C, E ) or located among striae (Fig. 7F, H ).

Etymology.

Named after China, where the species was found.

Ecology.

Measured in situ specific conductivity was 16.30 ± 0.09 mS∙cm-1, pH was 9.14 ± 0.01, and the water temperature was 15.5 ± 0.3 °C. Diatoma sinensis was found on submerged stones with yellow-brown surfaces, occurring with Berkeleya fennica Juhlin-Dannfelt (1882), Pinnularia qinghainensis Bing Liu & S. Blanco ( Deng et al. 2021), Entomoneis sinensis Bing Liu & D.M. Williams ( Long et al. 2022), E. qinghainensis Bing Liu and D.M. Williams ( Long et al. 2022), E. paludosa (W. Smith) Reimer ( Long et al. 2022), Ctenophora sinensis Bing Liu & D.M. Williams ( Liu et al. 2020), and some species of Navicula Bory ( Bory de Saint-Vincent 1822), Gyrosigma Hassall (1845), Nitzschia Hassall (1845), and Surirella Turpin (1828).

Figures

Figure 1. Map of Lake Qinghai showing the three sampling sites located in the lakeshore shallow waters (labeled 1, 2, and 3), on the western side of the lake. Inset map showing Lake Qinghai's location within China and the Qinghai province.

Figure 2. Diatoma sinensis sp. nov., LM A undigested specimens showing the cells always lying in girdle view with a rectangular shape (arrows) B-R seventeen valves showing a valve size diminution series, note the largest specimen (B) is three times longer than the smallest one (R). B illustration of holotype specimen. Scale bars: 50 μm (A); 10 μm (B-R).

Figure 3. Diatoma sinensis sp. nov., SEM, girdle view A a complete frustule B middle detail of A, showing the valve mantle and six bands (labeled B 1 to B 6) of which B 1 to B 4 are associated with the epivalve and B 5 and B 6 are assigned to the hypovalve C, D two apical details of A, showing the valve mantle, six bands (labeled B 1 to B 6), and the closed-open-closed-open-closed-open arrangement (labeled Cl = closed and Op = open) of the apices of six bands. Scale bars: 10 μm (A); 1 μm (B-D).

Figure 4. Diatoma sinensis sp. nov., SEM A a valve with a few girdle bands B a valve with an attached valvocopula C-E details of A showing the two rows of poroids in each band, a third very short row of poroids present (D, arrow), and the poroids continuing at one closed end (E, arrow) F-G details of B showing the valvocopula, note the two rows of poroids continuing at one closed end (F, arrow), silica sawtooth-shaped projections over virgae (G, H, arrows), and an open end (H). Scale bars: 5 μm (A, B); 1 μm (C-H).

Figure 5. Diatoma sinensis sp. nov., SEM, valvocopula A, B two valvocopulae showing the sawtooth-shaped projections and the open nature C-E details of A showing the two rows of poroids, note one open end (C, two arrows), a third very short row of poroids present at the middle (D, arrow) and one closed end (E) F-H details of B showing the two rows of poroids, note one open end (F, arrow), a third very short row of poroids present at the middle (G, arrow), and the different poroid shapes of the two rows of poroids. Scale bars: 5 μm (A, B); 2 μm (C-H).

Figure 6. Diatoma sinensis sp. nov., SEM, external view A, B two complete valves, note two rimoportulae per valve C-H details of Figs A, B showing the narrow sternum, the striae in groups separated by transverse clear areas, the slit-like external openings of rimoportulae, and the apical pore fields. Scale bars: 5 μm (A, B); 2 μm (C-H).

Figure 7. Diatoma sinensis sp. nov., SEM, internal view A, B two complete valves note the distribution of the ribs and two rimportulae per valve C-E details of A showing the distribution of the ribs and the rimportulae embedded in one rib at each apex (C, E, two arrows) F-H details of B showing the distribution of the ribs and the rimportulae located among striae (F, H, two arrows). Scale bars: 5 μm (A, B); 1 μm (C-H).