Diploneis peterseni Hustedt, 1937

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 : 238-240

Diploneis peterseni Hustedt ( Figs 246–252 )

The valves are lanceolate-elliptical with convex margins and bluntly round ends ( Figs 246–249, 252 ). The valve length is 13.5–21.0 μm, and the breadth is 6.0–7.0 μm. The axial area is linear throughout the whole length. The central area is small and rectangular, ca. 0.5–1.0 μm wide. The longitudinal canal is lanceolate, slightly expanding at the valve apices ( Figs 251, 252 ). The external openings of the canal are covered with volate occlusions ( Fig. 252 ). Externally, the raphe is straight with simple and slightly expanded proximal and distal ends ( Figs 250–252 ). Distally, the raphe branches terminate some distance from the valve margins ( Fig. 251 ). The striae are parallel in the middle of the valve, becoming radiate toward the valve apices, 26–27 in 10 μm. The single areola in each stria is covered with a volate occlusion that occupies less then half of the valve width ( Fig. 252 ). The hyaline area that covers part of the alveolate striae is lanceolate and broadly widens at the middle of the valve ( Fig. 252 ).

Ecology and Distribution: —M166A; M068A: found on rocks in shallow habitats in southern Lake Hövsgöl and in small streams in Arkhangai province .

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).