Diploneis latissima Jovanovska & Wilson & Hamilton & Stone 2023, sp. nov.

Diploneis latissima sp. nov. (LM Figs 567–576, SEM Figs 577–581) Valves are weakly asymmetric, elliptic-lanceolate with convex margins and round ends (Figs 567–577). Valve length is 31.5–48.5 μm and width is 23–29.5 μm. The axial area is narrow, linear to lanceolate (Fig. 568), patterned with irregular round ornamentations opened into small depressions that do not penetrate the silica cell wall (white arrow in Fig. 577). The axial area slightly widens into a longitudinally elongate and weakly asymmetric central area, 3.8–5.5 μm wide. Externally, the canal is linear to lanceolate, slightly expanded in the middle of the valve with two to three rows of cribrate areolae narrowing into one larger at the valve apices (Fig. 577). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Fig. 580). Externally, the raphe is filiform with slightly arched branches (Fig. 577). The distal raphe ends are unilaterally bent (Fig. 577). The raphe system is from the outside followed by irregularly positioned roundish structures located between the raphe and the row of areolae (white arrow in Fig. 577). Internally, the raphe is curved and placed in the depression formed by the longitudinal canal (Fig. 580). The striae are parallel at mid-valve becoming radiate towards the valve apices, 8–9 in 10 μm. Striae are biseriate throughout (Figs 578, 579). The striae are composed of round depressed areolae covered externally with fine pored cribra (ca. 40 poroids), 15–18 in 10 μm. The interstriae are distinct (Fig. 579). Internally, the alveoli open via a single elongate opening covered with a thin silica layer (Fig. 581). The valvocopula has serrated advalvar edges (Fig. 580). Type:— REPUBLIC OF ZAMBIA, Mulungushi River, at 1117 m elevation; mud, 0.1 m water depth, 14°17’45.6” S 28°32’54.8” E, E. Jovanovska & Z. Levkov, 27 th September 2021 (holotype designated here, circled specimen BM-108975! = Fig. 575, isotypes ANSP-GC17204!, CANA-129322!). Type material CANA-129322. Registration: http:// phycobank.org/103711 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S3n). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660299) and nuclear encoded 18S (SSU rDNA) sequence (GenBank accession: OQ 629558). Etymology:— The specific epithet ‘ latissima ’ refers to the broad width of the valve. Ecology and distribution:— This species was observed only in the Mulungushi River, which has a moderately alkaline pH (7.9), a low conductivity of 101 μS̔ cm-1, and low water transparency. It coexists with Diploneis dissipata sp. nov. and D. distinctebipunctata sp. nov. Main differential characters:— Valve width and shape, striae pattern, areolae offset, poroids ca. 40 per areola. Similar species:— Diplonies sanantoniensis Lange-Bertalot & Fuhrmann (2020: 123) and Diploneis dilatatafalsa Lange-Bertalot & Fuhrmann (2020: 36).

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