Hippodonta mudumalaiensis A. Vigneshwaran & B. Karthick 2022, sp. nov.
Creators: name: Vigneshwaran, Anbukkarasu
name: Wadmare, Neha
name: Karthick, Balasubramanian
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Chromista
Ochrophyta
Bacillariophyceae
Naviculales
Naviculaceae
Hippodonta
Hippodonta mudumalaiensis

description: Hippodonta mudumalaiensis A.Vigneshwaran & B.Karthick sp. nov. (Figs 2–39, Fig. 22 represents the holotype)
Description:— LM (Figs 2–29): Cells solitary, valves narrow-lanceolate to rhombic-lanceolate with broadly rounded apices. Valve length 13.0–20.0 μm, width 5.0–6.2 μm (n=67). Axial area narrow-linear, tilted, slightly asymmetric to the apical axis. Central area broadened with short single striae, shorter striae present at any one side; Striae radiate near centre and parallel near apices; no fascia is formed. Raphe linear-filiform, weakly pronounced, small teardrop-shaped and closely spaced central endings. Distal ends of raphe discernible in LM, equally pronounced as central endings, teardrop-shaped. Raphe distal ends positioned before terminal area or weakly advancing into slightly curved towards valve side. Terminal area distinguishable in LM, narrow, lunate and cap-like. Striae coarse, evenly spaced throughout valve, weakly to moderately radiate in the middle, becoming parallel or weakly convergent towards ends, 10–12/10 μm. Lineolae not discernible in LM.
SEM (Figs 30–39): Externally (Figs 30–34), valves with flat face and slightly convex central area (Figs 30–32). Axial area slightly asymmetric (Fig. 30). Proximal raphe endings strongly pronounced, teardrop-shaped and bent towards same side as distal ends (Figs 31, 32). Terminal pores of raphe distinct, advancing towards the terminal area and deflected towards one valve side (Figs 33, 34). Terminal septa clearly developed and bordered by semi circumpolar (Figs 33, 34). Slit-like elongated areolae positioned on apical valve mantle, 40–50 in 10 μm. Striae uniseriate throughout valve, simple apically elongated lineolate, 50–60/10 μm. Rarely near central area transapically elongated lineolate areolae (Fig. 32). Striae in the central area clearly shortened, one side longer than the other side (Figs 30, 32). Prominent hyaline area present throughout the valve mantle (Fig. 31).
Internally (Figs 35–39), striae placed in shallow linear depressions. Areolae covered by hymens. Central raphe endings simple, linear and gradually disappear (Fig. 38). Small wedge-shaped hyaline area present at centre. Distal raphe endings terminate on small defused helictoglossae (Figs 35, 36, 39). Terminal area internally prominent and bordered by hymenated linear depressions (Fig. 39).
Type:— INDIA. Masinagudi, Nilgiris, Tamil Nadu. Stream, 11°33’14.8” N, 76°37’21.6” E, altitude 940 m asl, was collected by Mr. Kannan Govindarajan. (holotype AHMA! Slide #1752 = Fig. 22). Type material AHMA #1752.
Habitat:— Epilithic, submerged stones in the stream. Water chemistry measurements includes pH of 7.35, nitrate (low range, NO 3 –) 0.03 mg ∙L- 1; dissolved oxygen (DO) 6.84 mg ∙L- 1; conductivity: 635 μS∙ cm-1; water temperature: 23.6 °C, total dissolved solids (TDS) 276 mg ∙L- 1.
Etymology:— The specific epithet “ mudumalaiensis ” refers to the name of the location from which this new taxon is identified.
description: Published as part of Vigneshwaran, Anbukkarasu, Wadmare, Neha & Karthick, Balasubramanian, 2022, A new species of Hippodonta Lange-Bertalot, Metzeltin & Witkowski (Bacillariophyceae, Naviculales) from the Western Ghats, India, pp. 219-228 in Phytotaxa 558 (2) on pages 222-223, DOI: 10.11646/phytotaxa.558.2.5, http://zenodo.org/record/7002983