Diploneis nitescens Cleve 1894

43. Diploneis nitescens (Gregory) Cleve (Figs 112, 113)

Basionym: Navicula smithii var. nitescens Gregory.

Type locality: Scotland; Lamlash Bay; Loch Fine.

References: Peragallo & Peragallo 1897–1908, p. 124, pl. 21, figs 1–3; Hustedt 1931 –1959, p. 640, fig. 1047; Podzorski & Håkansson 1987, p. 59, pl. 21, fig. 3; Hein et al. 2008, p. 52, pl. 26, figs 3, 4.

Morphometrics: Valves 42–71 (24–100) μm long, 19–26 (16–36) μm wide, transapical striae 7–9 (6–9) in 10 μm.

Remarks: This species is widespread from temperate to tropical regions as it is considered as the initial collection site and subsequent generations. Hustedt (1931 –1959) viewed the distribution of this taxon from the Mediterranean to northern Europe, but has been still reported from the tropical coasts. In the diatom atlas (Stidolph et al. 2012), which illustrate marine diatoms in tropical and subtropical habitats, Diploneis nitescens was the second most frequently recorded after Campylodiscus neofastuosus. The species has been reported from several islands in the Caribbean Sea (Foged 1984) and in the vicinity (Hein et al. 2008, Stidolph et al. 2012, Martínez-López et al. 2004, Siqueiros-Beltrones and Martínez 2017), the Pacific Ocean (Witkowski et al. 2000, Stidolph et al. 2012, Park et al. 2018), the Atlantic Ocean (Stidolph et al. 2012), and Philippines (Pozorski & Håkansson 1987, Stidolph et al. 2012). In addition to the results reported in atlas surveys, this taxon was seen in the other regions, the northern New Zealand (Stidolph 1980), the southern China (Jin et al. 1985), Brazil (Pacheco et al. 2016) and the coast of Iraq (Al-Handal et al. 2018). This taxon is scattered along the coast of the Atlantic Oceans from the Arctic to the Mediterranean (Witkowski et al. 2000), however, the specimens, which was collected from the East Greenland, presented in his illustrations are more close to Diploneis smithii (Brébisson) Cleve or its infraspecific taxa. In D. nitescens, longitudinal canals of valve are wide, but not swollen in the middle, and the outer margins of the canals are wider than half the width of the valve.

In South Korea, it was reported previously from the lagoon of the Seogwipo coast in Jeju Island (Park et al. 2017), and is encountered infrequently as an epiphytic species inhabiting the rock pools and pseudolagoons.