Cocconeis dirupta var. flexella (Janisch & Rabenhorst) 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 : 157

11. Cocconeis dirupta var. flexella (Janisch & Rabenhorst) Grunow ( Figs 33–37 , 90 )

Basionym: Janisch & Rabenhorst 1863, p. 7, pl. 1, fig. 11.

References: Hustedt 1933, p. 355, figs 809d–i; Witkowski et al. 2000. p. 105, pl. 39, figs 6, 7, pl. 51, figs 3–8; De Stefano & Marino 2001, p. 304; Lobban et al. 2012, p. 287, pl. 40, figs 4, 5; Stidolph et al. 2012, pl. 22, figs 25, 30.

Description: Valves broadly elliptical to almost circular, 16–31 μm long and 10–21 μm wide. SV: sternum moderately broad and sigmoid. Central area not developed, or often a short fascia with missing of a stria in either side of valve. Transapical striae radiate towards apices, crossed by hyaline and longitudinal rows, 20–23 in 10 μm. RV: striae slightly sigmoid, sternum very narrow. Central area transversely narrow fascia, not reaching to the margins. Transapical striae radiate, 20–21 in 10 μm.

Remarks: The collected variants are distinguished from the nominate variety by the sigmoid sternum of SV ( Hustedt 1933). This taxon has been reported from the Mediterranean, some islands of the Pacific and western Indian Oceans (Riaux-Robin et al. 2011, Lobban et al. 2012, Stidolph et al. 2012), Namibia of western Atlantic Ocean ( Witkowski et al. 2000), and Mexico (Siqueiros-Beltrones & Romero 2004). This taxon is distributed in warmer coasts and the Mediterranean. Here, it was frequently encountered as epiphytes on seaweeds and the benthic of the sandy bottom of the Seogwipo coast, South Korea.

Figures

FIGURES 25–44. LM micrographs of Cocconeis species (2). Figs 25, 26. Cocconeis cf. diruptoides, RV (Fig. 25) and SV (Fig. 26). Figs 27–32. C. dirupta var. dirupta, SVs (Figs 27–31) and RV (Fig. 32). Figs 33–37. C. dirupta var. flexella, SVs (Figs 34–36) and RVs (Figs 33, 37). Figs 38–41. C. delicata, RVs (Figs 38) and SVs (Figs 39, 40, 41). Figs 42–44. C. convexa, SVs (Figs 42, 43) and RV (Fig. 44). Scale bar = 10 μm (Figs 25–44).

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).