Pinnularia qinghainensis Bing Liu & S. Blanco, 2021

Deng, Li-Ying, Blanco, Saúl, Liu, Bing, Quan, Si-Jin & Long, Ji-Yan, 2021, Pinnularia qinghainensis: a new diatom species (Bacillariophyta) found in the brackish Lake Qinghai, China, Phytotaxa 483 (1), pp. 80-84 : 80-81

Pinnularia qinghainensis Bing Liu & S. Blanco sp. nov. ( Figs 1–25 )

LM: Valves linear with broadly rounded apices ( Figs 1–15 ), dimensions (n=31): 35–70 μm long, 8–11μm wide. Sternum narrow, widening towards central area. Central area hexagonal with three forms: reaching both margins (e.g. Figs 1, 5, 11 ), meeting one margin and bordering the other with few short striae (e.g. Figs 2, 3 ), or bordering both margins with a few short striae (e.g. Figs 8, 12, 15 ). Raphe filiform, straight. Proximal raphe ends slightly bent toward same side with drop-shaped central pores. Distal raphe fissures sickle-shaped, deflexed to same side. Striae mostly curved, radiate at middle, gradually becoming convergent when approaching apices. Striae 13–16 (often 14) in 10 μm at centre, 15–17 in 10 μm near apices. Longitudinal lines absent.

SEM: Valves linear with broadly rounded apices ( Figs 16 , 21 ). Central area hexagonal, reaching both margins ( Figs 17 , 23 ), or bordering both margins with a few short striae ( Figs 21, 22 ). External proximal raphe ends bent in one direction, slightly dilated ( Fig. 17 ). Distal raphe fissures hooked towards same side ( Figs 16, 18, 19 ). Internally, raphe branches straight, proximal raphe fissures curved towards same side, central nodule not raised ( Figs 22, 23 ); distal raphe terminating as helictoglossae ( Figs 24, 25 ). Striae mostly composed of 4 rows of small areolae (rarely 3 rows) ( Figs 16–20 ), covered by silicified plates ( Fig. 20 ); internally, alveoli open, their openings as depressed chambers.

Type:— CHINA. Qinghai province: Lake Qinghai, a sampling point near the lakeshore (see Liu et al. 2020, fig. 1, sampling site 1), 36°50’34” N, 99°42’39” E, 3210 m asl, Bing Liu , 19 th July 2019 (holotype BM! 98361= Fig. 2 ; isotype JIU! G202002 = Fig. 3 ) .

Etymology: —Named after Lake Qinghai, where the species was found.

Ecology: —The following environmental parameters were measured in the field: Electrical conductance 16296.7 ± 86.2 µS∙ cm-1; pH 9.14 ± 0.01; water temperature 15.5 ± 0.3 °C.

Similar taxa: Pinnularia boliviana S. Blanco, Álvarez-Blanco & Cejudo-Figueiras (in Blanco et al. 2013: 15), P. rhombarea var. halophila Krammer (2000: 76) and P. halophila Krammer (1992: 146 ; see also Krammer 2000: 137) all live in brackish water and in some respects are similar to P. qinghainensis . Pinnularia boliviana differs from P. qinghainensis by its lower stria density (12–13 vs. 13–16 in 10 μm), its wider valves (10.8–16.4 vs. 8–11 μm), and its fascia (in P. qinghainensis the central area may not constitute a fascia). Pinnularia rhombarea var. halophila has broader valves (12–15 vs. 8–11μm) and lower stria density (10–11 vs. 13–16 in 10 μm). Pinnularia halophila has broader valves (17–22 vs. 8–11μm) and much lower stria density (8–9 vs. 13–16 in 10 μm). Pinnularia brebissonii ( Kützing 1844: 93) Rabenhorst (1864: 222) also has a lower stria density than P. qinghainensis (12–13 vs. 13–16 in 10 μm).

Pinnularia qinghainensis is only known from the type locality and is a rare species (its relative abundance is ca. 0.4%). The diatom samples that included P. qinghainensis were scraped off from stone surfaces immersed in brackish water, hence, the species may be recognized as a brackish-water epilithic diatom. Most of the companion species (e.g. Ctenophora sinensis Bing Liu & D.M. Williams (in Liu et al. 2020: 119), Entomoneis spp. , Halamphora spp. , Berkeleya sp. , Triblionella spp., Brachysira sp. and Surirella spp. ) in the samples are either marine or brackish-water diatoms which will be reported later.

Figures

FIGURES 1–15. Pinnularia qinghainensis sp. nov., LM. Figs 1–15. 15 valves showing size diminution series, note hexagonal central area (see a sketch in Fig. 5), which can reach the middle margins (e.g. Figs 1, 5, 11), bordering one margin and the other with few short striae (e.g. Figs 2, 3), or bordering both with a few short striae (e.g. Figs 8, 12, 15). Fig. 2 = holotype specimen. Fig. 3 = isotype specimen. Scale bar = 10 μm (in Fig. 1).

FIGURES 16–20. Pinnularia qinghainensis sp. nov., SEM external view. 16. Complete valve. 17. Detail of centre in Fig. 16, note hexagonal central area and slightly bent central raphe ends. 18, 19. Detail of pole in Fig. 16 showing curved distal raphe fissures and striae composed of 4 rows of small areolae. 20. Detail of striae showing small areolae occluded by silica plates. Scale bar = 10 μm (Fig. 16), 1 μm (Figs 17–20).

FIGURES 21–25. Pinnularia qinghainensis sp. nov., SEM internal view. 21. Complete valve. 22. Detail of centre in 21, note hexagonal central area bordering margins with few short striae. 23. Detail of centre of valve showing hexagonal central area reaching margins. 24, 25. Details of two poles in Fig. 21. Scale bar = 10 μm (Fig. 21), 1 μm (Figs 22–25).