Tryblionella hunanensis Bing Liu & Rioual 2026, sp. nov.
Year: 2026
Type: article
Abstract: Tryblionella hunanensis Bing Liu & Rioual sp. nov. Figs 8, 9, 10, 11, 12 Holotype. The specimen circled on the slide DIA 2026003, illustrated here as Fig. 8 A, deposited in the Herbarium of Jishou University (JIU), China. Registration: http://phycobank.org/106075. Type locality. China • Hunan Province, Yongle River (a tributary of the largest river, Xiang River, in Hunan Province, China). Sampling location (26°55'08"N, 113°35'55"E, 119 m a. s. l.) in a riffle, collected by Bing Liu, 24 March 2024. Description. LM (Fig. 8). Valves panduriform with cuneate to acute apices. Valve dimensions (n = 31): length range 37–53 μm, width range 8.9–13.2 μm at constricted middle parts. Valve surfaces slightly undulated from side to side. Axial sternum absent. Transapical ribs parallel, across valve face continuously, 9–12 in 10 μm. Raphe system eccentric, located only along one side of valve. Fibulae visible, rectangular to square (e. g., Fig. 8 D, two arrows), 7–10 in 10 μm. SEM (Figs 9, 10, 11, 12). Valves panduriform with elevated transapical ribs continuously across valve surface (Figs 9, 10). Dense silica granules present on the valve surface, striae uniseriate, 34–36 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. 9 B – D, double-headed arrows). Marginal ridge is a standing silica lamella, composed of a bottom part with a row of pores produced along the junction between the distal mantle and the base of the marginal ridge, and a solid top part with a distinctly lobed margin (Figs 9, 10). Four to seven longitudinal grooves are produced in the raphe canal wall on the side of valve (Figs 9 A, 10 A, 10 B). Distal mantle shallow, lacking ornamentations (Fig. 10 C – F). Distal raphe fissures curved (Figs 10 C, 11 B, curved arrows). Proximal mantle markedly deep, composed of two parts: advalvar part (composed of bar-like ribs and narrow, rectangular openings), and abvalvar part (hyaline part without ornamentations) (Fig. 11). A row of poroids produced in the raphe canal wall on the side of the proximal mantle (Fig. 11 B – D, arrows). Inner openings of areolae rounded, rimmed. Fibulae squat, mostly apically elongated (Fig. 12), two median fibulae farther apart (Fig. 12 A, B, arrows). Helictoglossae small (Fig. 12 C, D, curved arrows). Etymology. Named after Hunan Province, where the species was found (specific locality is Yongle River). Vernacular name. The Chinese name for Tryblionella hunanensis is “湖南盘杆藻.” Ecology and distribution. Tryblionella hunanensis sp. nov. was collected from the mud sediments on the stone surfaces in the Yongle River. There are numerous associated species, with the most abundant being Ctenophora hunanensis Bing Liu & Rioual, Cymbella turgidula Grunow, Grunowia tabellaria (Grunow) Rabenhorst, Gyrosigma kuetzingii (Grunow) Cleve, Hippodonta capitata (Ehrenberg) Lange-Bertalot, Metzeltin & Witkowski, Nitzschia palea (Kützing) W. Smith, Tryblionella calida, Ulnaria fanjingensis Bing Liu, and several species of Cocconeis Ehrenberg, Fragilaria Lyngbye, Gomphonella Rabenhorst, Luticola D. G. Mann, Navicula Bory, Planothidium Round & Bukhtiyarova, Sellaphora Mereschowsky, and Surirella Turpin. The following environmental parameters were measured in the field: conductivity was 111.7 ± 0.8 μS cm – 1, pH was 7.6 ± 0.04, and water temperature was 22.3 ± 0.3 ° C. The environmental variables and the composition of the diatom assemblage suggest alkaline and mesotrophic conditions. So far, T. hunanensis has been found at the type locality and in East Dongting Lake. Comments. Tryblionella hunanensis sp. nov. is characterized by its panduriform valve outline with cuneate to acute apices, slightly undulate valve surface, elevated transapical ribs continuous across the valve face and short bar-like ribs connecting the raphe canal wall, uniseriate striae, squat, mostly apically elongated fibulae, and a marginal ridge composed of a bottom part with a row of pores produced along the junction between the distal mantle and the base of the marginal ridge and a solid top part with a distinctly lobed margin. A review of the literature revealed few species similar to T. hunanensis sp. nov. The species most similar to T. hunanensis are T. calida and T. dongtingensis. All three species have similar valve outlines and overlapping morphometric ranges, and they can coexist in the same habitat in East Dongting Lake. However, T. calida has almost flat valve surfaces (Fig. 1), whereas T. hunanensis has a more undulate valve surface (Fig. 13). Furthermore, the solid top part of the marginal ridge in T. calida is straight (see Fig. 2), whereas in T. hunanensis it is distinctly lobed (see Fig. 14). Tryblionella hunanensis also differs from T. dongtingensis in the structure of the raphe canal wall on the valve side (in the former, it is grooved, whereas in the latter, it is smooth) and the marginal ridge (in the former, its bottom part has no slit-like fenestrae, whereas slit-like fenestrae are present in the latter).
Language: English
Topic: Diatoms and Algae Research
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7204158661