Stauroneis dharwarensis Wadmare & B.Karthick, 2022

Wadmare, Neha & Karthick, Balasubramanian, 2022, Revisiting two Stauroneis Ehrenberg (Bacillariophyta) from H. P. Gandhi’s Diatom collection: Notes on Ultrastructure, Types and Nomenclature, Phytotaxa 555 (1), pp. 42-52 : 47-48

Stauroneis dharwarensis Wadmare & B.Karthick nom. nov., stat. nov. ( Figs 19–41 , Fig. 24 represents the lectotype)

Basionym:— Stauroneis anceps f. indica in Gandhi 1959a, Ceylon Journal of Science (Biology Section), p. 104, 105, fig. 25 (here reproduced as Fig. 19 ).

Type:— INDIA. Dharwar, Karnataka. Dharwar pools from paddy and millet fields watercourses during rains, 15°26’34.8” N, 74°54’43.2” E. Mr. H. P. Gandhi on 14 th August 1949 .

Lectotype (designated here):—Agharkar Research Institute ( AHMA) Gandhi Collection! Slide- Sr 48, here illustrated as Fig. 24 .

Description:—LM ( Figs 19–31 ): Valves broadly lanceolate with constricted, subrostrate to rostrate apices. Length 32.0–64.0 µm, breadth 12.0–15.0 µm. Axial area narrow, widening at centre. Stauros bow-tie shaped, widening towards valve margin. Raphe slightly coarse with straight central raphe ends, terminal raphe fissures unilaterally deflected. Striae strongly radial punctate, 17–19/10 µm. Areolae punctate to transapically elongated, discernible in LM. (n= 36).

SEM ( Figs 32–41 ): Externally ( Figs 32–36 ), valves linear-lanceolate with axial area narrow throughout but wider at centre ( Figs 32, 36 ). Central raphe ends tear-drop shaped ( Figs 32, 33 ). Terminal raphe fissures continuing onto mantle ( Figs 34, 35 ). Striae uniseriate, composed of transapically elongated areolae, 24–28 in 10 µm ( Figs 33–35 ). Internally ( Figs 37–41 ), stauros broad, thickened and expanded ( Figs 37, 38, 40 ). Central raphe ends slightly deflected, terminating onto well-developed stauros ( Figs 38, 40 ). Terminal raphe fissures terminating onto helictoglossae ( Figs 38, 39 ). Striae radiate, areolae with hymen occlusions ( Figs 39–41 ).

Remarks:—Valve dimensions of the specimens examined in the present study have a wider size range than H. P. Gandhi in the original description- length 54.0–58.0 µm; width 14.4 µm (see Table 2 ). This taxon is also observed in Sr 46, collected by H. P. Gandhi from the same site at the same time and date as Sr 48.

Etymology:—The specific epithet “ dharwarensis ” refers to the type locality Mugad, Dharwar district, Karnataka, where H. P. Gandhi originally collected the sample.

Figures

FIGURES 19–31. Stauroneis dharwarensis Wadmare & B.Karthick nom. nov., stat. nov., 19. Original illustration of Gandhi (1959a: 104, 105, Fig. 25). 20–31. Light micrographs (DIC) from the type material (AHMA Sr 48), Fig. 24 represents the lectotype. Scale bar = 10 µm.

FIGURES 32–36. Stauroneis dharwarensis Wadmare & B.Karthick nom. nov., stat. nov., SEM, external valve views. 32, 36. External views of an entire valve. 33. Stauros with tear-drop central raphe ends. 34, 35. Deflected terminal raphe fissures. Scale bars = 4 µm (Figs 32–36).

FIGURES 37–41. Stauroneis dharwarensis Wadmare & B.Karthick nom. nov., stat. nov., SEM, internal valve views. 37, 38. Internal views of an entire valve. 37, 39.Apices showing terminal raphe fissures as helictoglossae. 40. Stauros thick bearing deflected central raphe ends. 39–41. Areolae with hymen layer. Scale bars = 4 µm (Figs 37–41).