Cocconeis pseudomarginata var. intermedia Grunow

Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, Phytotaxa 528 (3), pp. 149-179 : 166

19. Cocconeis pseudomarginata var. intermedia Grunow ( Figs 73–76 , 88, 89 )

Basionym: Grunow 1867, p. 13, pl. 1, fig. 6.

References: Suzuki et al. 2001c, p. 94, figs 1–26; Suzuki et al. 2008, p. 277.

Description: Valves elliptical, 26–68 μm long, 14–51 μm wide. SV: sternum broadly lanceolate, the ends of sternum enlarged and pear-shaped, connected to the submarginal hyaline area, a longitudinal line bisecting striae between sternum and valve margins. The outer surface of sternum longitudinally depressed. Transapical striae radiate towards the apices, 25–30 in 10 μm, striae composed of elongated areolae. RV: raphe weakly sigmoid, sternum very narrow, the terminal ends of the sternum expanded with a crescent-shaped hyaline area, resulting the raphe distant from the apices. Longitudinal depression between the raphe and valve margins. Central area small rhombic. Transapical striae radiate towards the apices, 23–28 in 10 μm in the inner parts of valve.

Remarks: This taxon differs from the nominate variety, Cocconeis pseudomarginata , in that the raphe is slightly sigmoid and transapical striae of SV are dense.

The distribution area of the species is quite limited, compared with the nominate variety, but prefer warmer marine coasts in view of localities, Cape of Good Hope, Nicobar Islands, Luzon, Manilla, and Tahiti ( Fourtanier & Kociolek 2011). More recently, it has frequently been found in Japan ( Suzuki et al. 2001c). In the present study, it was frequently encountered as epiphytes on seaweeds along the Seogwipo coast of South Korea.

Figures

FIGURES 69–76. LM micrographs of Cocconeis species (5). Figs 69–72. Cocconeis pseudomarginata, RVs (Figs 69, 72) and SVs (Figs 70, 71) (Figs 69 and 70, a complete valve). Figs 73–76. C. pseudomarginata var. intermedia, RVs (73, 76) and SVs (Figs 74, 75). Scale bar = 10 μm (Figs 69–76).

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).