Diploneis krammeri Lange-Bertalot & Reichardt, 2000

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 : 227

Diploneis krammeri Lange-Bertalot & Reichardt ( Figs 113–134 )

Valves are elliptical-lanceolate with convex margins and round ends ( Figs 113–124 ). The valve length is 23.0–34.0 μm, and the valve breadth is 13.0–17.0 μm. The axial area is linear to lanceolate, expanding toward the round to slightly elongate central area. Internally a thick silica plate covers the longitudinal canal throughout ( Fig. 125 ). Externally the central area is elongate, 2.5–3.5 μm wide. From outside the longitudinal canal is linear to lanceolate, expanded in the middle of the valve with one to two rows of areolae. The external openings of the canal areolae are covered with cribra similar to those on the striae, from which the canal areolae are separated with a thick hyaline area ( Figs 129, 130, 133 ). From inside, the longitudinal canal is covered with thick silica forming a “depression” where the raphe is placed ( Figs 125 , 156 ). Externally, the raphe is straight with expanded proximal ends slightly bent to the same side of the valve and positioned within a small depression ( Figs 129, 130, 133 ). From outside the distal raphe endings finish with short terminal fissures bent to the same side of the valve ( Figs 129, 131, 132, 134 ). Internally, the raphe is straight and simple, placed in the “depression” formed by the longitudinal canal ( Fig. 125 ). The proximal raphe endings are the only raphe section reaching the height of the longitudinal canal in contrast to the only slightly elevated distal ends ( Figs 125–127 ). The striae are radiate, 11(12) in 10 μm, with round areolae covered with cribra ( Fig. 128 ), 13–15 in 10 μm. The external areolar openings increase in size and become more complex in structure, or are biseriate toward the valve margins ( Figs 129, 131, 132, 134 ). Internally the alveoli open via a single continuous and elongate opening covered with a fine silica layer ( Figs 125, 126 ).

Observations: —In the original description of D. krammeri the longitudinal canal is composed of one row of areolae throughout the whole length ( Lange-Bertalot & Reichardt 2000: pl. 4, figs 1–10, 12). However, on the SEM illustrations the external openings of the longitudinal canal are composed of two rows of areolae in the middle of the valve narrowing into one at the valve apices ( Lange-Bertalot & Reichardt 2000: pl. 5, figs 1–5). The longitudinal canal in Lake Hövsgöl populations are composed of one row of areolae throughout, which unambiguously fits the LM illustrations given by Lange-Bertalot & Reichardt (2000).

Ecology and Distribution: —M063A; M248A; M273A; M274A; M280A; M329A: distributed in shallow to deep benthic habitats throughout Lake Hövsgöl in the sediments and marl .

Figures

FIGURES 113–128. Diploneis krammeri, LM and SEM valve views. Figs 113–124. LM valve views. Fig. 125. Internal view of the whole valve. Fig. 126. Detailed view of the internal proximal raphe ends. Fig. 127. Internal view of the distal raphe endings. Fig. 128. Close view of the external cribrate occlusions. Scale bars = 10 μm (Figs 113–124); 5 μm (Figs 125, 127); 2 μm (Fig. 126); 1 μm (Fig. 128).

FIGURES 129–134. Diploneis krammeri, SEM external valve views. Fig. 129. View of the whole valve. Fig. 130. Proximal raphe endings. Fig. 131. View of the whole frustule. Fig. 132. Showing the structure of the striae at the valve mantle. Fig. 133. Detailed view of the valve central area. Fig. 134. Distal raphe endings with short deflected terminal fissures. Scale bars = 5 μm (Figs 129, 131); 2 μm (Figs 130, 132–134).

FIGURES 152–165. Diploneis exigua, LM and SEM valve views. Figs 152–159. LM valve views. Figs 153, 156, 158. Specimens from the holotype slide, M272A. Fig. 160. External view of the entire valve. Fig. 161. External distal raphe endings with short terminal fissure. Fig. 162. Broken valve, showing the external and internal opening of the alveolate striae. Fig. 163. Internal view of the distal raphe endings. Fig. 164. Showing the simple proximal raphe endings from the interior. Fig. 165. Internal view of the whole valve. Scale bars = 10 μm (Figs 152–160, 165); 3 μm (Fig. 161); 2 μm (Fig. 162); 1 μm (Figs 163, 164).