Diploneis cf. eximia Metzeltin, Lange-Bertalot & Nergui, 2009

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 : 240

Diploneis cf. eximia Metzeltin, Lange-Bertalot & Nergui ( Fig. 253 )

The valve is elliptical to linear-elliptic with slightly convex margins and bluntly rounded ends. The valve length is 67.5 μm, and the breadth 27.5 μm. The axial area is narrow and parallel, slightly expanded near the large transapically elliptical central area, which is 7.0 μm wide. The longitudinal canal is lanceolate to linear expanding in the middle with two to three rows of areolae that coalescence into one to two towards the valve apices. The raphe branches are straight and simple with distinctly expanded proximal ends. The striae are radiate, 10 in 10 μm, composed of one row of round to rectangular areolae, 10 in 10 μm.

Observations:— LM images of Diploneis eximia are not included in the original description, and therefore it is rather difficult to make comparisons ( Metzeltin et al. 2009). Due to the similar valve outline and the structure of the longitudinal canal the population from Lake Hövsgöl is identified as Diploneis cf. eximia . Further analysis of the type material is preferable in order to fully understand the identity of D. eximia and its potential relationship to populations here identified as D. cf. eximia .

Ecology and Distribution: —M331A: found in shallow sediments of central Lake Hövsgöl and tychoplanktonic in a lake in Khentii province ( Metzeltin et al. 2009).

Figures

FIGURES 253–271. LM and SEM external valve views. Fig. 253. Diploneis cf. eximia, LM valve view. Figs 254, 255. Diploneis cf. minuta, SEM external valve views. Fig. 254. Valve view. Fig. 255. Proximal raphe endings. Figs 256–259. Diploneis sp. 1. Fig. 256. LM valve view. Fig. 257. Central area with proximal raphe endings, SEM. Fig. 258. Distal raphe endings, SEM. Fig. 259. View of the entire valve, SEM. Figs 260–269.Diploneis sp. 2, LM valve views. Fig. 270. Diploneis sp. 3, LM valve view.Fig. 271. Diploneis sp. 3, LM valve view. Scale bars = 10 μm (Figs 253, 256, 260–271); 5 μm (Figs 254, 259); 2 μm (Figs 255, 257, 258).