Isthmia minima Harvey & Bailey, 1862

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

6. Isthmia minima Harvey & Bailey ( Figs 16, 17 )

Type locality: Rio Janeiro; Sooloo Sea .

References: Navarro 1981, p. 616, figs 16–20, as Isthmia enervis Ehrenberg ; Andresen 1995, p. 103, figs 1–9; Hein et al. 2008, p. 20, pl. 5, fig. 7; Lobban et al. 2012, p. 251, pl. 7, figs 4–6.

Morphometrics: Valves 209 (188–300) μm in pervalvar length, 63 (67–80) μm in valve diameter. Areolae larger, areolae on a stria 2.5 in 10 μm in valve, striae 3.7 in 10 μm in valve and 9 in 10 μm in girdle bands.

Remarks: Isthmia minima is characterized by distinct invaginated cribra on the valve mantle above the valvocopulae ( Andresen 1995). The taxon occurred in Madagascar ( Sournia 1968), in Puerto Rico ( Navarro 1981), in the Bahamas ( Hein et al. 2008), in Guam ( Lobban et al. 2012). It is listed on the diatom catalogue of Caribbean Sea ( Navarro & Hernández-Becerril 1997) and Florida Bay ( Frankovich & Wachnicka 2015). It is a typical tropical taxon living in warmer oceans. In the Seogwipo coast, it was found once as an epiphyte on seaweeds in a rock pool, representing a new record for South Korea.

Figures

FIGURES 12–21. Diatom taxa of Seogwipo coast in Jeju Island (2). Figs 12, 18, 19. Pseudictyota reticulata. Figs 13–15. Biddulphia gruendleri. Figs 16, 17. Isthmia minima. Figs 20, 21. Biddulphia tridens. Scale bars = 10 μm.