A new species of Hippodonta Lange-Bertalot, Metzeltin & Witkowski (Bacillariophyceae, Naviculales) from the Western Ghats, India Author Vigneshwaran, Anbukkarasu 0000-0003-4766-6873 Biodiversity and Palaeobiology Group, Agharkar Research Institute, Pune, Maharashtra, India- 411004 & Department of Botany, Savitribai Phule Pune University, Pune, Maharashtra, India- 411007 & vigneshwar 1296 @ gmail. com; https: // orcid. org / 0000 - 0003 - 4766 - 6873 vigneshwar1296@gmail.com Author Wadmare, Neha 0000-0003-1188-3489 Biodiversity and Palaeobiology Group, Agharkar Research Institute, Pune, Maharashtra, India- 411004 & Department of Botany, Savitribai Phule Pune University, Pune, Maharashtra, India- 411007 & nehawadmare @ aripune. org; https: // orcid. org / 0000 - 0003 - 1188 - 3489 nehawadmare@aripune.org Author Karthick, Balasubramanian 0000-0003-4066-2458 Biodiversity and Palaeobiology Group, Agharkar Research Institute, Pune, Maharashtra, India- 411004 & Department of Botany, Savitribai Phule Pune University, Pune, Maharashtra, India- 411007 & karthickbala @ aripune. org; https: // orcid. org / 0000 - 0003 - 4066 - 2458 karthickbala@aripune.org text Phytotaxa 2022 2022-08-15 558 2 219 228 http://dx.doi.org/10.11646/phytotaxa.558.2.5 journal article 123004 10.11646/phytotaxa.558.2.5 7d9fa0b4-3d40-4af0-956d-f05a8beb5dca 1179-3163 7002983 Hippodonta mudumalaiensis A.Vigneshwaran & B.Karthick sp . nov . ( Figs 2–39 , Fig. 22 represents the holotype ) FIGURES 2–29. Hippodonta mudumalaiensis sp. nov. , LM (DIC) from the type material (AHMA #1752). 2–29. Showing the valve variability of the population. Fig. 22 represents the holotype. Scale bar = 10μm. 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 ). FIGURES 30–34. Hippodonta mudumalaiensis sp. nov. , SEM from the type material (AHMA #1405), external views. 30, 31. Views of the entire valve. 32. Central area. 33, 34. Valve apices. Scale bars = 1 μm (Figs 30–34). 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.