Diploneis oculata (Brébisson) Cleve

Jovanovska, Elena, Levkov, Zlatko & Edlund, Mark B., 2015, The genus Diploneis Ehrenberg ex Cleve (Bacillariophyta) from Lake Hövsgöl, Mongolia, Phytotaxa 217 (3), pp. 201-248 : 238

Diploneis oculata (Brébisson) Cleve ( Figs 236–245 )

Valves are elongate-elliptical with parallel to slightly convex margins and bluntly round ends ( Figs 236–244 ). The valve length is 13.0–24.5 μm, and the breadth is 5.0–7.5 μm. The axial area is linear, expanding into a small rectangular central area, ca. 0.5–1.0 μm wide. The longitudinal canal is linear, with a rectangular central nodule ( Figs 243–245 ). At the valve apices the axial area expands slightly on the both sides of the valve ( Figs 243, 244 ). Externally, the canal is composed of one row of areolae throughout the whole length, covered with volate occlusions ( Figs 243–245 ). The raphe is straight and slightly expanding into small drop-like central pores ( Figs 244, 245 ). The distal raphe endings are simple and slightly expanded, terminating some distance from the valve margins ( Figs 243, 244 ). The striae are parallel in the middle of the valve, becoming slightly radiate at the valve apices, 22–24 in 10 μm. The areolae of the alveolate striae are not discernible with LM and SEM observations, due to the volate occlusions that occupy less then half of the valve width ( Figs 244, 245 ).

Ecology and Distribution: —M068A; M077A; M248A; M273A; M287A: found in shallow to deep habitats including epilithon and sediments throughout Lake Hövsgöl .

Figures

FIGURES 236–252. LM and SEM external valve views. Figs 236–245.Diploneis oculata. Figs 236–242. LM valve views. Fig. 243. View of the whole valve overlaid by the girdle bands. Fig. 244. View of the entire valve. Fig. 245. Proximal raphe endings and detailed view of the external alveolate openings covered with vola. Fig. 246–252. Diploneis peterseni, LM and SEM external valve views. Figs 246–249. LM valve views. Fig. 250. Valve central area with simple proximal raphe endings. Fig. 251. Distal raphe endings. Fig. 252. View of the entire valve. Scale bars = 10 μm (Figs 236–242, 246–249); 5 μm (Fig. 252); 2 μm (Figs 243–245, 250); 1 μm (Fig. 251).