Trigonium formosum (Brightwell) Cleve, 1867

Joh, Gyeongje, 2021, Distribution and frequent occurrence of diatom taxa (Bacillariophyta) inhabiting warmer oceans in Seogwipo coast of Jeju Island, southernmost Korea, Phytotaxa 517 (1), pp. 1-67 : 11

7. Trigonium formosum (Brightwell) Cleve ( Figs 5, 6 )

Basionym: Triceratium formosum Brightwell.

Synonym: Biddulphia formosa (Brightwell) Jørgensen.

Type locality: not given.

Reference: Hustedt 1927 –1930, p. 819, fig. 481.

Morphometrics: Valves 175 (120–375) μm long, 187 (125–390) μm in side length of triangle, transapical striae 4 in 10 μm, areoale on a stria 4 (1.5–4.5) in 10 μm.

Remarks: This taxon is distributed in the littoral of warmer marine waters, and in the southern regions of Europe ( Hustedt 1927 –1930), in the planktons of Carrie Bow Cay in Belize of the Central America ( Hargraves 1982), in the Caribbean Sea of Colombia ( Lozano-Duque et al. 2010), and in Guam ( Theriot et al. 2010). It is a typical tropical taxon, although its distribution is not so wide. In South Korea, this taxon was already reported in the southwestern sea of Korean Peninsula in 1984 ( Shim & Park 1984), and very rare epiphyte on seaweeds along the Seogwipo coast in Jeju Island.

Figures

FIGURES 2–11. Diatom taxa of Seogwipo coast in Jeju Island (1). Figs 2–4. Pseudictyota dubium. Fig. 5, 6. Trigonium formosum. Fig. 7. Triceratium reticulum. Fig. 8. Asteromphalus flabellatus. Fig. 9. Aulacodiscus orientalis. Fig. 10, 11. A. affinis. Scale bars = 10 μm.