Gomphoneis lata (Skabitchevsky) Kociolek & Kulikovskiy

Kociolek, John P., Kulikovskiy, Maxim S. & Solak, Cüneyt N., 2013, The diatom genus Gomphoneis Cleve (Bacillariophyceae) from Lake Baikal, Russia, Phytotaxa 154 (1), pp. 1-37 : 5

Gomphoneis lata (Skabitchevsky) Kociolek & Kulikovskiy , comb. nov. ( Figs 32–39 , 368 –375)

Basionym: Gomphonema latum Skabitchevsky (1987: 74, pl. 2, figs 1–6).

Valves linear-lanceolate clavate with apices broadly rounded. Length 41–61 µm, breadth 11–15 µm. Axial area narrow, straight, expanded to form a distinct, rectangular central area bordered by 2–3 shortened striae on either side, with 4–9 isolated stigmoids. Raphe lateral, straight, with external proximal ends dilated and rounded. External distal raphe ends deflected onto the mantle at the headpole, bisecting the apical pore field at the footpole. Striae composed of two rows of fine areolae. Striae radiate at the center, nearly radiate to barely parallel at poles. Striae 9–11/ 10 µm. Apical pre fields composed of distinct rows of porelli. Septa and pseudosepta present at the apices.

In the SEM, the external portion of the valve is dominated by thickened, distinct interstriae that alternate with the striae ( Figs 368–371 ). The axial area, interstriae and central area appear to be elevated from the level of the areolae. Striae are composed on 2, sometimes 3 rows of areolae ( Figs 369, 371 ). At the central area the stigmoids are round and appear to occur in slightly sunken depressions ( Fig. 370 ). The poles have the distal raphe ends bent onto the mantle ( Figs 369, 371 ), while at the footpole the apical pore fields appear as compressed striae ( Fig. 371 ). Internally, an overall view shows the presence of septa at both poles (Figs 372, 374). The internally elevated, elliptical central nodule bears the proximal raphe ends (Figs 372, 373, 375). The proximal raphe ends are recurved in the same direction. Around the base of the central nodule there 4 isolated stigmoids (Figs 373, 375). The stigmoidal openings appear slit like and occluded by teeth-like projections (Figs 373, 375). Girlde bands have one row of rectangular openings (Figs 372, 374, 375).

Figures

PLATE 2: LM. Figs 18–31: Gomphoneis parahastata sp. nov. Figs 32–39: G.lata. Scale bar = 10 µm for all figures.

PLATE 10: SEM. Figs 368–371: Gomphoneis lata. External valve views. Fig. 368: Overall valve view showing robust interstriae, thickened central area, straight raphe and isolated stigmoids. Fig. 369: Headpole with raphe extending well onto valve mantle. Fig. 370: Central area with doubly punctate striae ending as single areolae and isolated stigmoids much larger than the areolae. Fig. 371: Footpole, with apical pore field bisected by distal raphe end curving onto mantle, porelli elongate and right next to the striae, and some striae composed of 2 or 3 rows of areolae.