Microcostatus meridionalis Peszek, M. Rybak & Kochman-Kedziora, 2021

Rybak, Mateusz, Kochman-Kedziora, Natalia & Peszek, Lukasz, 2021, Description of four new terrestrial diatom species from Luticola and Microcostatus genera from South Africa, PhytoKeys 182, pp. 1-26 : 1

Microcostatus meridionalis Peszek, M. Rybak & Kochman-Kedziora sp. nov.

Holotype.

Slide no. 20-093 stored at the South African National Diatom Collection (SANDC) at North-West University, Potchefstroom, South Africa.

Isotype 1.

Slide no. 27525 and unmounted material with same number at the Szczecin Diatom Collection (SZCZ) hosted by the University of Szczecin.

Isotype 2.

Slide no. 2018/426 and unmounted material with the same number at the University of Rzeszow, Poland.

Type locality.

Jonkershoek Nature Reserve, Western Cape, South Africa, 33°59.695'S, 18°58.726'E, leg. W. Morek and B. Surmacz, 20.09.2018.

Etymology.

The name refers to the area from where the new species is described (lat. meridional - southern).

Description. LM (Fig. 4A-O ). Valves lanceolate to elliptical-lanceolate with convex valve margins. Valve dimensions (n = 25): length 7.5-14.0 µm, width 3.5-4.5 µm. Striae in light microscopy invisible. Raphe branches straight. Raphe located in elevated sternum, asymmetrically concave at the centre. Proximal raphe endings clearly visible, drop-like in shape and widely spaced. Distal raphe endings barely visible, curved in the same direction.

Description. SEM (Fig. 4P -AA). Longitudinal depressions present next to the sternum (Fig. 4P-U ). Striae strongly radiating (36-42 in 10 µm), composed of one row of square to rounded areolae, externally not occluded, except central area (Fig. 4P-X ). Central area large, lanceolate in shape, composed of fully externally silicified areolae composing striae (Fig. 4P-T, X ). Raphe straight, filiform, located in raised and asymmetrically-constricted sternum (Fig. 4P-V, Y, Z ). Proximal raphe fissures slightly asymmetrical drop-shape (Fig. 4U, Y, Z ). Distal raphe fissures hooked and deflected to the same direction (Fig. 4V, X-Z ). Transverse microcostae most prominent at the area near to valve margin (area of striae not covered by silica) (Fig. 4U-Y ). A row of rounded to slightly elongated pores (3-5) present on the valve mantle, at the valve apices (Fig. 4U, Y, Z ). Internally areolae occluded by hymenes. Raphe branches straight, forming small and elongated helictoglossae on distal endings, proximal endings drop-shaped. The central area is broad, corresponds in shape to external depression (Fig. 4AA).

Figures

Figure 4. Holotype population of Microcostatus meridionalis Peszek, M. Rybak & Kochman-Kedziora, sp. nov. A-O LM images of valve views P-AA SEM images P-T images of entire valve external views U-Z view on valve central area and valve apices AA internal view of valve. Scale bars: 10 µm (A-O), 5 µm (P, Q), 4 µm (R), 3 µm (S-U, Y-AA), 2 µm (V, W), 1 µm (X).