Cocconeis pseudomarginata Gregory

Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, Phytotaxa 528 (3), pp. 149-179 : 162-166

18. Cocconeis pseudomarginata Gregory ( Figs 69–72 )

Basionym: Gregory 1857, p. 492, pl. 9, fig. 27.

References: Hustedt 1933, p. 359, figs 813a–c; Romero & Navarro 1999, figs 1–6, 13–15, 20–31; Riaux-Gobin et al. 2014a, p. 176, f, 33, 34.

Description: Valves broadly elliptical to ovoid, 19–54 μm long, 10–41 μm wide. SV: sternum wide lanceolate, the terminal ends of sternum enlarged and pear-shaped, extending to submarginal hyaline line, and a longitudinal row of areolae between sternum and the submarginal hyaline lines. Transapical striae in inner parts of valve radiate towards the apices, 22–29 in 10 μm, areolae on a stria transapically elongated. RV: raphe straight and linear, sternum very narrow, crescent-shaped hyaline area at the terminal ends of sternum, resulting the ends of raphe distant from the apices. Central area small lanceolate or circular. The valve depressed between the raphe and valve margins. Transapical striae radiate towards the apices, 21–30 in 10 μm in the inner parts of valve.

Remarks: This species is similar to Cocconeis multiperforata De Stefano, Mario & Mazzella and the two may be confused in the image of light microscopy. However, the comprehensive comparison of relevant reports and data of SEM ( Romero & Navarro 1999, De Stefano et al. 2000, Mori et al. 2002, Riaux-Gobin et al. 2014a) allowed to identify the following differences: the former has uniseriate striae in the SV, a crescent shape of the hyaline area at the terminal ends of the raphe, and more than 22 of striae in the SV, while these parameters of the latter are biseriate, pear-shaped, and less than 20, respectively.

This taxon is widespread along marine coasts worldwide ( Hustedt 1933); it has been collected in many places, ranging from Puerto Rico to Scotland ( Romero & Navarro 1999). It was reported near Cape Town of South Africa ( Giffen 1970), in the southeastern Pacific Ocean and the Caribbean Sea ( Romero & Navarro 1999), common in Kattegat of Baltic Sea ( Witkowski et al. 2000), and in Japan ( Mori et al. 2002). In South Korea, this species was reported as planktons and periphytes off the coast of Jeju Island ( Lee et al. 1990, 1991), and in this survey, occurred infrequently as epiphytes in the Seogwipo coast.

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).