Surirella qinghainensis Bing Liu & Rioual 2025, sp. nov.

Surirella qinghainensis Bing Liu & Rioual sp. nov. Figs 7, 8, 9, 10, 11 Holotype. Specimen circled on slide DIA 2025002 (= Fig. 7 B), deposited in the Herbarium of Jishou University (JIU), China. Registration: http://phycobank.org/105637. Type locality. China. Qinghai Province, Lake Qinghai, a sampling site near the lakeshore, 36°50'34"N, 99°42'39"E, 3210 m asl., collected by Bing Liu, July 19 th, 2019. Description. LM (Fig. 7). Valve outlines ovate with broadly rounded headpole and cuneate footpole. Valve dimensions (n = 34): length range 38–57 μm, width range 31–50 μm at its widest region. Costa-stria bundles (CSBs) distinct, alternating with over-fibula ribs (OFRs) from pole to pole (labelled in Fig. 7 E). CSBs radiate throughout valve surface. Fibulae visible, short (judged by OFRs, labelled in Fig. 7 E), 4–6 in 10 μm. A marginal row of costae produced on the wall of raphe canal (e. g., Fig. 7 B, arrows), 16–18 in 10 μm. SEM (Figs 8 – 11). Externally, raphe canal located directly on mantle (Fig. 8 A, B), and wall of raphe canal bearing a marginal row of costae (Fig. 8 B, arrows; Fig. 8 E, double-headed arrows). Valve surface presents three differentiable areas (labelled A 1, A 2, and A 3 in Fig. 8 B). Distal raphe endings straight, interrupted at both headpole and footpole (Fig. 8 C, D). Surface costae mostly slightly raised, not reaching valve midline except at two poles (Fig. 8 A, B). Each CSB often composed of ca. 2–4 costae and 3–5 striae (Fig. 8 F). Outside openings of areolae slit-like (Fig. 8 D). Striae multiseriate (sometimes becoming uniseriate at valve middle, Fig. 9 A, D), composed of ca. 2–5 rows of areolae (Figs 8 D, 9, 10), 16–20 in 10 μm (measured at the valve margin from SEM images, n = 3). Surface siliceous warts and reticulate thickenings produced on costae and between adjacent two costae, respectively (Fig. 8 A-F). Each mantle sinking corresponding to each over-fibula rib (Fig. 9 C, arrows). Internally, wall of raphe canal not growing conspicuously into cell cavity, leaving portulae visible (Fig. 10). Fibulae slim, much shorter, spanning ca. 1 / 8 of valve width, far away from valve midline except at two poles. Marginal trough-like depressions present around entire raphe canal (Fig. 10). Raphe continuous at headpole (Fig. 10 C, arrow) whereas interrupted at footpole (Fig. 10 B, two arrows). 2–4 portulae produced between two adjacent fibulae (Fig. 10 E, F, arrows). Inner openings of areolae rounded, rimmed (Fig. 10 B – F). Etymology. Named after Lake Qinghai, where this species was found. Vernacular name. The Chinese name is “ 青海湖双菱藻 ”. Ecology and distribution. Surirella qinghainensis was commonly found in the surface sediment on the surface of the stones collected in Lake Qinghai with S. brightwellii and S. ectorii. It is more frequent than S. ectorii but less than S. brightwellii. So far, S. qinghainensis has only been found in the type locality and can be considered a brackish diatom species endemic to Lake Qinghai.