Navicula fuxianensis Y. - L. Li 2025, sp. nov.

Navicula fuxianensis Y.-L. Li, sp. nov. (Figs 1–10) Description: LM (Figs 1–4): Valves narrowly lanceolate with long-protracted and wide ends, nearly symmetrical about the apical axis, with clearly convex margins. Length 80.0–107.5 µm, width 14.5–17.0 μm, length/width ratio 5.5–6.4, median 5.9 (n = 30). Raphe branches slightly undulate. External central raphe ends simple, linear, forming pore-like expansions. External terminal raphe fissures weakly deflected. Axial area narrow and linear, not or slightly expanded towards the centre of the valve. Central area small, slightly expanded transapically, oval-elliptical, nearly symmetrical, with a pair of obviously shortened striae proximally. Striae uniseriate and radiate throughout with broader spacing in the middle. Striae in the middle portion 7–9 in 10 μm, up to 11 in 10 μm toward the ends. Lineolae coarse, ca. 26 in 10 µm. SEM: Valve exterior (Figs 5–7): the central raphe ends deflected towards secondary valve side, drop-like, expanded central pores (Figs 5, 6). The terminal fissures appear hooked towards the secondary side of the valve (Fig. 7). Striae uniseriate (Figs 5–7). Areolae round-elliptical around axial area, slit-like toward the valve margin and mantle (Fig. 6). Valve interior (Figs 8–10): striae uniseriate, formed by mostly slit-like and occasionally round-elliptical areolae, separated by robust silica ribs (Figs 8–10). Central raphe opening discontinuous, intermissio present (Figs 8, 9). Terminal raphe ends offset slightly and end in small helictoglossae (Figs 10). Type: CHINA. Yunnan Province: Fuxian Lake, freshwater, 24°24.870' N, 102°50.590' E, elevation 1720 m a.s.l., 28 March 2005, surficial sediment samples collected by Prof. Yan-Ling Li (Holotype FXH 200532810 in Coll. Yan-Ling Li, Yunnan University, Kunming, China = Fig. 1; Isotype YUNGL20220420, Harbin Normal University, Harbin, China). Etymology:— fuxianensis, referring to the type locality from which the new species was obtained. Ecology: — Navicula fuxianensis is known from the surface sediments of Lake Fuxian, situated at 1720 m a.s.l. At this site, diatom assemblages were dominated by Aulacoseira granulata (Ehrenberg) Simonsen (1979: 58), Cyclotella krammeri Håkansson (1990: 263), Cyclotella rhomboideo-elliptica Skuja (1937: 49), Navicula fuxianturriformis Y.- L. Li, J.-S. Guo & Kociolek (Zhang et al. 2022: 143), Fragilaria crotonensis Kitton (1869: 110), Stephanodiscus hantzschii Grunow (in Cleve et Grunow 1880: 115), Stephanodiscus minutulus (Kützing) Cleve et Möller (1882: 300), and several unidentified species of Achnanthes Bory de St.-Vincent (1822b: 79) and Amphora Ehrenberg ex Kützing (Kützing 1844: 152).