Cocconeis pelta 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 : 161-162

16. Cocconeis pelta A. Schmidt ( Figs 20, 21 )

Basionym: Schmidt 1874, p. 93, pl. 3, fig. 17.

References: Hustedt 1933, p. 361, fig. 815; Witkowski et al. 2000, p. 111, pl. 41, figs 7–10; Sar et al. 2003, p. 91, fig. 33.

Description: Valves elliptical, 15–16 μm long, 11–12 μm wide. SV: sternum slightly very broadly lanceolate to elliptical, depressed making a distinct marginal rim, irregularly punctate. Central area not developed. Transapical striae developed in the margins, radiate towards the apices, 17–18 in 10 μm. RV: raphe straight, sternum broadly elliptical like the SV. Transapical striae in the margins radiate towards the apices.

Remarks: The local specimens are smaller than the dimensions reported in referred literatures. Though the fine morphology of the three taxa seen with SEM differs, Cocconeis pelta is similar to C. peltoides Hustedt and C. fluminensis H. Peragallo & M. Peragallo in the morphology of SV under LM. Commonly, the three species have longitudinal costae in the median area of the SV, but the first species is distinguished from the second and the third taxon in that there is no striae in the inside of the longitudinal costae ( Sar et al. 2003). The first species has a similar stria density with the second, while it is distinguished from the higher density than the third.

This species has been reported from the western Baltic Sea ( Witkowski et al. 2000), European coasts in the North Atlantic and the Patagonian coasts of Argentina ( Sar et al. 2003). In South Korea, this taxon was reported firstly as the epipsammic from the Nakdong River estuary ( Joh 2012), and in this survey, very rare in small rock pools (St. 2) and salt marshes (St. 4) of the Seogwipo coast.

Figures

FIGURES 3–24. LM micrographs of Cocconeis species (1). Figs 3–5. Cocconeis stauroneiformis, RV (Fig. 3) and SVs (Figs 4, 5). Figs 6–8. C. costata, SVs (Figs 6, 7) and RV (Fig. 8). Figs 9–11. C. capensis, SVs. Figs 12–19. C. distans, SVs (Figs 12, 15, 17–19) and RVs (Figs 13, 14, 16) (Figs 14 and 15, 16 and 17, complete valve). Figs 20, 21. C. pelta, SV (Fig. 20) and RV (Fig. 21). Fig. 22. C. cf. pinnata, SV. Figs 23, 24. C. clandestina, SVs. Scale bar = 10 μm (Figs 3–24).