Tryblionella dongtingensis Bing Liu & Rioual 2026, sp. nov.
Year: 2026
Type: article
Abstract: Tryblionella dongtingensis Bing Liu & Rioual sp. nov. Figs 5, 6, 7 Holotype. The specimen circled on the slide DIA 2026002, illustrated here as Fig. 5 A, deposited in the Herbarium of Jishou University (JIU), China. Registration: http://phycobank.org/106074. Type locality. China • Hunan Province, East Dongting Lake. Sampling location (29°19'7"N, 112°47'32"E, 39 m a. s. l.) in the lake littoral zone, collected by Bing Liu, 5 March 2023. Description. LM (Fig. 5). Valves linear-lanceolate, slightly constricted in the middle on both sides, with wedge-shaped apices. Valve dimensions (n = 30): length range 33–65 μm, width range 10.3–12.1 μm at constricted middle parts. Valve surface undulated from side to side. Axial sternum absent. A longitudinal fold is present along the valve midline (e. g., Fig. 5 G, double-headed arrow), dividing the valve face into two non-coplanar halves. Transapical ribs more evident on one half of valve surface than on the other when observed at a given focal plane, 9–14 in 10 μm, parallel except approaching apices, where they become radiate. Raphe system eccentric, located along one side of valve only. Fibulae visible, short, rectangular (e. g., Fig. 5 E, F, arrows), 6–9 in 10 μm. SEM (Figs 6, 7). Transapical ribs elevated, some run across the valve face continuously whereas others terminate at the middle longitudinal fold (Fig. 6 D, E, curved arrows). Striae uniseriate, 38–40 in 10 μm (measured on SEM images, n = 3). A longitudinal row of bar-like ribs produced along the raphe canal wall, from pole to pole (Fig. 6 C – F, arrows). Central nodule present (Fig. 6 C, curved arrow). Distal raphe fissures curved (Fig. 6 D). Marginal ridge is a high standing silica lamella, composed of a bottom part with long slit-like fenestrae (Fig. 6 F, two curved arrows) and a top part with a serrate margin (Fig. 6 C – E, double-headed arrows). Distal mantle very shallow, lacking ornamentations (Fig. 6 F). Inner openings of areolae rounded, rimmed (Fig. 7 D). Proximal mantle markedly deep so that it often hides the short fibulae (Fig. 7 A). Proximal mantle composed of two parts: advalvar part (composed of bar-like ribs and narrow, rectangular openings), and abvalvar part (hyaline without ornamentations). Fibulae squat, often hidden by the deep proximal mantle (Fig. 7 A, B, D, curved arrow), helictoglossa small (Fig. 7 D, arrow). Etymology. Named after Dongting Lake, where the species was found. Vernacular name. The Chinese name for Tryblionella dongtingensis is “洞庭湖盘杆藻.” Ecology and distribution. Tryblionella dongtingensis sp. nov. was collected from the surface sediments in the littoral zone of East Dongting Lake. Associated species included Craticula ambigua D. G. Mann, C. cuspidata D. G. Mann, Dorofeyukea kotschyi Kulikovskiy, Kociolek, Tusset & T. Ludwig, Gyrosigma dongtingense Bing Liu & Rioual, G. kuetzingii (Grunow) Cleve, Hantzschia amphioxys Grunow, Surirella angusta Kützing, S. suecica Grunow, Tryblionella calida, T. hungarica (Grunow) Frenguelli, Ulnaria rhombus D. M. Williams, and several species of Navicula Bory, Nitzschia Hassall, and Sellaphora Mereschkowsky. The following environmental parameters were measured in the field: conductivity was 494 ± 0.9 μS cm - 1, pH was 8.4 ± 0.06, and water temperature was 27.8 ± 0.3 ° C. The environmental variables and the composition of the diatom assemblage suggest alkaline and mesotrophic to eutrophic conditions. So far, T. dongtingensis has been found only at the type locality. Comments. Tryblionella dongtingensis sp. nov. is characterized by its linear-lanceolate valve outline with wedge-shaped apices, undulate valve surface from side to side, elevated transapical ribs and short bar-like ribs connecting the raphe canal wall, uniseriate striae, short fibulae, and a high marginal ridge composed of a bottom part with elongate slit-like fenestrae and a solid top part with an undulate margin. A review of the literature revealed few species similar to T. dongtingensis sp. nov. The most similar species to T. dongtingensis is T. calida, and they can coexist in the same habitat. The two species, however, differ in their morphometry. Tryblionella calida has narrower valves (8.6–10.6 μm vs. 10.3–12.1 μm), a higher density of transapical ribs (15–17 in 10 μm vs. 9–14 in 10 μm), and a higher density of fibulae (9–10 in 10 μm vs. 6–9 in 10 μm). In addition, T. calida has almost flat valve surfaces (Fig. 1), whereas T. dongtingensis has an undulate valve surface (Fig. 5). Furthermore, the marginal ridge in T. calida has a plain top margin (see Fig. 2), whereas in T. dongtingensis it has an undulate top margin (see Fig. 6).
Language: English
Topic: Diatoms and Algae Research
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7204180604