Stauroneis lacuspowaiensis 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 : 44

Stauroneis lacuspowaiensis Wadmare & B.Karthick nom. nov., stat. nov. ( Figs 1–18 , Fig. 4 represents the lectotype)

Basionym: — Stauroneis phoenicenteron f. capitata in Gonzalves & Gandhi 1953, The Journal of Indian Botanical Societ y, p. 256, fig. 92 (here reproduced as Fig. 1 )

Heterotypic synonym: — Stauroneis nobilis f. capitata H.Kobayasi (in Kobayasi & Ando 1977)

Type:— INDIA. Mumbai (then Bombay), Maharashtra. Powai Lake pavements having encrustations with dead vegetable matter, 19°7’37.2” N, 72°54’14.4” E, Mr. H. P. Gandhi on 6 th March 1945.

Lectotype (designated here):—Agharkar Research Institute ( AHMA) Gandhi Collection! Slide- Sr 5, here illustrated as Fig. 4 .

Description:—LM ( Figs 1–8 ): Valves narrowly linear-lanceolate, having large, capitate apices with slight undulate sides ( Fig. 5 , arrow). Length 98.5–103.0 µm, breadth 16.5–18.0 µm. Axial area broad widening near centre. Stauros slightly broad, rectangular. Raphe thick with straight central raphe ends, and sickle-shaped terminal raphe fissures with bifurcation ( Fig. 7 , arrowhead). Striae parallel at centre and radiate towards apices, 18–23/10 µm. Areolae irregularly punctate ( Fig. 4 , double arrowheads), discernible in LM. (n= 21).

SEM ( Figs 9–18 ): Externally ( Figs 9–14 ), central raphe ends terminating on stauros ( Figs 9, 10, 12 ). Raphe filiform ( Fig. 12 ). Terminal raphe fissures sickle-shaped, continuing onto mantle ( Figs 11, 13 ). Striae uniseriate, composed of irregularly placed, transapically elongated, slit-like areolae ( Fig. 14 , double arrowheads). Internally ( Figs 15–18 ), stauros small, thickened and elevated with tunnel gap ( Figs 15, 17 , arrowheads). Terminal raphe fissures terminating onto helictoglossae ( Figs 15, 16, 18 ). Areolae rounded to transapically elongated, 16–20 in 10 µm ( Fig. 17 , double arrowheads).

Remarks:—Valve dimensions of the specimens examined in the current study have a smaller size range than the dimensions given by H. P. Gandhi in the original description length 113.4–120.0 µm; width 21.6 µm (see Table 1 ). In addition, previous studies based on Gandhi’s material observed certain morphometry discrepancies ( Karthick & Kociolek 2012, Kale et al. 2017).

Etymology:—The specific epithet “ lacuspowaiensis ” refers to the type locality Powai Lake, Mumbai, where H. P. Gandhi originally collected the sample.

Figures

FIGURES 1–8. Stauroneis lacuspowaiensis Wadmare & B.Karthick nom. nov., stat. nov., 1. Original illustration of Gonzalves & Gandhi (1953: 256, fig. 92). 2–8. Light micrographs (DIC) from the type material (AHMA Sr 5), Fig. 4. represent the lectotype. 4. Irregularly punctate areolae (double arrowheads). 5. Valve with slight undulate sides (arrow). 7. Terminal raphe fissures with bifurcation (arrowhead). Scale bar = 10 µm.

FIGURES 9–14. Stauroneis lacuspowaiensis Wadmare & B.Karthick nom. nov., stat. nov., SEM, external valve views. 9, 10. External views of an entire valve. 11, 13. Terminal raphe fissures continuing on mantle. 12. Stauros with straight central raphe ends. 14. Irregularly placed areolae (double arrowheads). Scale bars = 4 µm (Figs 9, 10, 12); 1 µm (Figs 11, 13, 14).

FIGURES 15–18. Stauroneis lacuspowaiensis Wadmare & B.Karthick nom. nov., stat. nov., SEM, internal valve views. 15. Internal view of an entire valve. 15, 17. Elevated stauros possessing tunnel gap (arrowheads). 17.Areolae irregular covered with hymen structures (double arrowheads). 16, 18. Terminal raphe fissures with helictoglossae. Scale bars = 4 µm (Figs 15–18).