Mychonastes koreanus H. Lee, T. Kim, & J. Ki, 2025

Lee, Ha-Eun, Kim, Taehee & Ki, Jang-Seu, 2025, Description of Mychonastes koreanus sp. nov. (Sphaeropleales, Chlorophyceae) isolated from the Yun River, Republic of Korea, Phytotaxa 693 (4), pp. 255-269 : 258

Mychonastes koreanus H. Lee, T. Kim, & J. Ki sp. nov. ( Fig. 2A–E )

Description: Cells are green to light yellowish-green, single, planktonic, and spherical. Cell wall is sculptured in SEM observation. They are 1.5 to 3.5 μm in diameter, with an average of 2.75 μm. They lack a mucilaginous envelope and stalks. They do not form colonies , except during propagation two or four autospores after sporulation remain attached for a short time. The chloroplast is single, parietal, and cup-shaped without pyrenoids. This species is distinguished from other Mychonastes species by the nucleotide composition of the rRNA ITS2 sequence and its secondary structure.

Etymology: The name of the country ( Korea) where the species was discovered was reflected.

Holotype: A permanent microscopic slide, NIBRCL0000117313 in the Herbarium at the National Institute of Biological Resources, from cultured strain SMU-GA001.

Type locality: Yun-gang River, Toegang-ri, Sabeolguk-myeon, Sangju-si, Gyeongsangbuk-do, Korea (36°31'36.3"N, 128°15'50.5"E).

Distribution: To date, Mychonastes koreanus has only been observed in this type of locality. At the time of collection, the pH was 8.0, and the water temperature was 17.1 °C.

Gene sequences: partial 18S rRNA, ITS1, 5.8S, ITS2, and partial 28S rRNA gene sequences with GenBank accession number OR914224.

Figures

FIGURE 2. Light microscopy (A–C) and scanning electron microscopy (SEM) (D, E) micrographs of Mychonastes koreanus sp. nov. and its cell size distribution (F). A: Light micrographs of cells. Scale bar=10 µm. B: A single cell with a cup-shaped chloroplast (marked with an arrowhead). C: The moment of propagation with two autospores. D: SEM micrographs of cells. Scale bar=10 µm. E: SEM micrographs of sculptured cell wall. Scale bar=1 µm. F: Size range of the cells, represented in two ways: bar graph=the number of cells in the specific diameter range; line graph=normal distribution values.