Geissleria triundulata P. Nayak, M. Thacker & B. Karthick, sp. nov.
Creators: name: Nayak, Pratyasha
name: Thacker, Mital
name: Hamilton, Paul B.
name: Karthick, Balasubramanian
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Chromista
Bacillariophyta
Bacillariophyceae
Cymbellales
Cymbellaceae
Geissleria
Geissleria triundulata

description: Geissleria triundulata P.Nayak, M.Thacker & B.Karthick sp. nov. (Figs 1–40, Fig. 3 represents the holotype)   
Description:—LM (Figs 3–26): Valves linear-lanceolate, with slightly triundulate margins and weakly protracted, broadly rounded apices. Length 16.0–23.5 µm, width 5.5–6.5 µm (n=60). Raphe filiform, straight. Axial area narrow and linear, slightly widening towards centre of valve. Central area rectangular, formed by one shortened stria on each valve side. Middle striae located at considerable distance from neighbouring two. An isolated stigma present near central nodule. Proximal raphe ends straight and slightly enlarged. Distal raphe endings not discernible in LM. Striae slightly radiate to subparallel throughout, alternatively longer and shorter around central nodule, 22–24 in 10 µm. Areolae not discernible in LM. Annulus barely discernible in LM.  
SEM (Figs 27–40): Externally raphe branches straight and filiform (Fig. 27). Proximal raphe endings slightly, roundly enlarged (Figs 27, 32–33). Distal raphe ends hooked and curved in same direction at apices and continue on valve mantle (Figs 27–29). Axial area narrow, linear, and widened towards rectangular central area, defined by one shortened stria on each side of valve. A single isolated slit-like stigma present close to central nodule. Central area hyaline and slightly elevated (Figs 32–33). Striae uniseriate composed of transapically elongated lineolate areolae, around 90 in 10 μm. A pair of sub-polar areolae present at both sides of the raphe at valve ends (Figs 28–29). Presence of slit-like transapically elongated structure at apices (Figs 30–31, arrowheads). Internally, entire valve showing organisation of striae, location of stigma and remnants of copulae (Fig 34). Proximal raphe endings slightly hooked and deflecting on same side, terminating onto central nodule of protruding sternum (Figs 37–38). Distal raphe endings terminate in small helictoglossae (Figs 35–36). Virgae raised between slightly sunken striae (Figs 37–38). Warty outgrowths along the long sides of the sub-polar areolae present (Figs 39–40, arrowheads).  
 Type:— INDIA. Maharashtra: Pune, Mutha River, near Jambhali, 18.388833°N, 73.650861°E, 580 m. a.s.l, 25 May 2022. (Holotype AHMA! 3776 = Fig. 3).   
 Habitat:—Epilithic sample collected from the river bank.   
 Etymology:—The specific epithet “ triundulata ” refers to the valve outline of the species.   
 Ecology and distribution:— G. triundulata sp. nov. was found in low electrical conductivity (59.2 µs/cm) and slightly alkaline pH (7.95) waters. The dominant genera in the sample are Pantocsekiella K.T.Kiss & Ács (2016: 62), Fragilaria Lyngbye (1819:185), Sellaphora (Mereschkovsky 1902: 187), and Navicula. As of now, this taxon is known only from the type locality.
description: Published as part of Nayak, Pratyasha, Thacker, Mital, Hamilton, Paul B. & Karthick, Balasubramanian, 2024, Geissleria triundulata sp. nov., a new freshwater diatom (Cymbellaceae, Bacillariophyta) from the Mula-Mutha River Basin, India, pp. 109-119 in Phytotaxa 661 (1) on pages 112-115, DOI: 10.11646/phytotaxa.661.1.9, http://zenodo.org/record/13218342