Distribution and frequent occurrence of diatom taxa (Bacillariophyta) inhabiting warmer oceans in Seogwipo coast of Jeju Island, southernmost Korea Author Joh, Gyeongje text Phytotaxa 2021 2021-08-30 517 1 1 67 http://dx.doi.org/10.11646/phytotaxa.517.1.1 journal article 10.11646/phytotaxa.517.1.1 1179-3163 8061058 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 .