Cocconeis conspicua A. Schmidt

Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, Phytotaxa 528 (3), pp. 149-179 : 154

4. Cocconeis conspicua A. Schmidt ( Figs 87 , 105 )

Basionym: Schmidt et al. 1894b, pl. 196, figs 27–30.

Description: Valves broadly elliptical, but slightly oblique along apical axis, 31–38 μm long, 24–30 μm wide. SV: sternum broadly elliptical and sigmoid. Longitudinal hyaline area bisecting twice striae between sternum and valve margins, a row of very large puncta on the outer hyaline area, the largest punctum in the area 1.5 μm in diameter. A longitudinal line crossing striae between the sternum and inner hyaline area. Transapical striae radiate towards the apices, 26–27 in 10 μm, striae composed of elongated areolae. RV: No RV observed, only trace of sigmoid raphe could be seen.

Remarks: This taxon is characterized by a marginal axial hyaline area on each part of the SV and the presence of large round structures in these hyaline areas. There are no descriptions of this taxon except for the illustrations at the times of the naming. From the original valve drawings ( Fig. 92 ) of Schmidt et al. (1894b), valves are 27–38 μm long and 18–29 μm wide. At that times, it was found in Kings Mill Islands (now Gilbert Islands) and Samoa in the Pacific Ocean, in Bissex of Barbados in the West Indies, and in Singapore ( Schmidt et al. 1894b). However, it is placed on the checklist of marine diatoms in the Caribbean Sea ( Navarro and Hernández-Becerril, 1997). Based on the localities found to date, it is a typical tropical taxon. Very rare in a few samples as epiphytes on seaweed in rock pools (St. 2) of Seogwipo coast; it is herein newly described for South Korea.

Figures

FIGURES 84–87. LM micrographs of Cocconeis species (7). Figs 84–86. Cocconeis pellucida, SVs (Figs 84, 85) and RVs (Figs 85, 86), internal view (Fig. 84) and external view of SV (Fig. 86). Fig. 87. C. conspicua, SV. Scale bars = 10 μm (Figs 84–87).

FIGURES 100–105. SEM micrographs of Cocconeis species (10). Figs 100–102. Cocconeis convexa, the external view of SV (Fig. 100), the external view of RV (Fig. 101) and internal view of RV (Fig. 102). Figs 103, 104. C. stauroneiformis, the external views of SV. Fig. 105. Cocconeis conspicua, SV, the original drawing of Schmidt (1894b, pl.196, fig. 27). Scale bars = 1 μm (Fig. 103), 2 μm (Figs 100–102, 104), 10 μm (Fig. 105).

FIGURES 88–93. SEM micrographs of Cocconeis species (8). Figs 88, 89. C. pseudomarginata var. intermedia, the external view (Fig. 88) and internal view of SVs (Fig. 89). Fig. 90. C. dirupta var. flexella, the external valve of SV. Figs 91–93. C. cf. diruptoides, the external view of SVs (Figs 91, 92), and the internal view of RV (Fig. 93). Scale bars = 5 μm (Figs 88, 89), 2 μm (Figs 90, 92), 1 μm (Fig. 93).