Navicula watveae C. Radhakrishnan, Kociolek & B. Karthick, 2020

Radhakrishnan, Cheran, Pardhi, Samadhan, Kulikovskiy, Maxim, Kociolek, J. Patrick & Karthick, Balasubramanian, 2020, Navicula watveae sp. nov. (Bacillariophyceae) a new diatom species from the Western Ghats, India, Phytotaxa 433 (1), pp. 20-26 : 21-22

Navicula watveae C. Radhakrishnan, Kociolek & B. Karthick sp. nov. ( Figs 1–38 )

LM ( Figs 1–38 ):—Valves lanceolate to rhombic-lanceolate, with broadly-rounded apices, not protracted. Valve dimensions (n=70): length 44 – 73 μm, width 8 – 12 μm. Axial area linear-lanceolate. Sternum visibly developed. Central area small, bow-tie shaped, with 2 – 3 sometimes 4 irregularly shortened striae. Raphe filiform to slightly lateral, straight to weakly curved near the drop-like proximal raphe endings, which deflect towards the secondary side. Proximal and distal raphe fissures deflected in the same direction. Distal raphe endings hooked. Striae radiate in the center and becoming convergent to the apices, 10 – 11 in 10 μm. Lineolae clearly visible 25 – 30 in 10 μm. Voigt discordance evident on secondary side.

SEM ( Figs 39–48 ):—Externally, the valves have a distinctive, bow-tie shaped central area, narrow axial area and expanded areas at the apices ( Fig. 39 ). Proximal raphe endings are dilated slightly ( Figs 39, 41 ), while the distal raphe endings are strongly hooked ( Figs 40, 42 ) and deflected towards the secondary side ( Fig. 39 ). Striae composed of slitlike lineolae.

Internally, the valve has a raised, longitudinal sternum that contains the raphe ( Figs 44 – 45 ). Around the rib is an asymmetrically-widened, longitudinally-oriented thickened area ( Figs 44 – 48 ). Central area comprised of laterally-expanded fascia. Proximal raphe endings are straight, not dilated ( Fig. 47 ) Distal raphe endings terminate as helictoglossae, which are offset from the median rib ( Figs 46, 48 ). There is an expanded unornamented area at the apices ( Figs 46, 48 ). Striae are occluded internally with ellipsoidal hymens.

Type: —Slide #2 – 81, Sample #91; date of sampling is 11 October 2013 and collected by Karthick Balasubramanian and deposited at the Diatom Collection, Agharkar Research Institute Herbarium ( AHMA), Pune , India .

Etymology: —The specific epithet honors Dr. Aparna Watve, Biome, Pune, India for her efforts in understanding the ecology of rocky outcrops and associated environments. In particular, we recognize her efforts in the documentation of biodiversity of Kaas Plateau region of the Western Ghats.

Type locality: — INDIA, Maharashtra, A stream located below the roadside waterfalls on Kaas Road, Satara (17.67840°N, 73.95867°E; elevation 989 m a.s.l.) (holotype: Agharkar Research Institute Herbarium ( AHMA!).

Associated diatom taxa: —Some of the dominant taxa occurred along with the Navicula watveae are Navicula escambia (R.M. Patrick) Metzeltin and Lange-Bertalot (2007: 162) and undescribed species belongs to Nitzschia Hassal (1845) and Geissleria Lange-Bertalot & Metzeltin (1996) .

Figures

FIGURES 1–38. Navicula watveae LM, DIC. Figs 1–38. Valve view. Scale bars= 10 µm.

FIGURES 39–43. Navicula watveae SEM. Figs 39–40, 43. External view of whole valve showing striae pattern and raphe structure. Figs 40, 42. External view of apices showing the deflection of distal raphe endings. Fig. 41. External view of central valve showing the proximal raphe ending. Scale bars=2 µm.

FIGURES 44–48. Navicula watveae SEM.Figs 44, 45. Internal view of whole valve. Figs 46, 48. Internal view of apices showing internal areolae pattern and distal raphe endings. Fig. 47. Internal view of center valve showing proximal raphe endings. Scale bars=2 µm.