Diploneis sp. 2

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 : 241

Diploneis sp. 2 ( Figs 260–269 )

The valves are elliptic-lanceolate with weakly convex margins and rounded ends. The valve length is 23.5–34.0 μm and the valve breadth is 9.5–15.0 μm. The axial area is narrow lanceolate, expanding toward the small, round to elongate central area, 2.0–2.5 μm wide. The longitudinal canal is narrow, linear to lanceolate, expanded in the middle of the valve with two rows of areolae. The raphe is straight with expanded proximal ends. Striae are radiate, 13–16 in 10 μm, with round areolae, 14–16 in 10 μm.

Observations: —The similarities in valve outline and in the structure of the longitudinal canal makes Diploneis sp. 2 closely allied to D. stoermeri . The structure of the central area (2.0–2.5 μm in Diploneis sp. 2 vs. 1.5–4.0 μm in D. stoermeri morphotype 2) and the stria density (14–16 in 10 μm in Diploneis sp. 2 vs. 12–15 in 10 μm in D. stoermeri morphotype 2) somehow separates them. Diploneis krammeri is another similar taxon, differing in the structure of the longitudinal canal and in the striae density (14–16 in 10 μm in Diploneis sp. 2 vs. 11–12 in 10 μm in D. krammeri ). Additional LM and SEM analyses are necessary to determine the identity of Diploneis sp. 2 .

Ecology and Distribution: —M272A; M274A; M280A; M281A; M284A; M291A: distributed in shallow (4 m) to deep (20 m) sediment, Chara , and marl collections from northern Lake Hövsgöl .

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).