Nagumoea serrata, a new diatom species (Bacillariophyceae) found on seagrass from the south-eastern coast of Africa (Indian Ocean)

A novel diatom species belonging to the genus Nagumoea is described based on detailed light and scanning electron microscopy observations. The new taxon was found abundantly in several samples collected from seagrass on the southernmost coasts of Mozambique, Southern Africa. While the new species shows characters (e.g. scalariform valvocopula, fibulae of complex shape and structure) consistent with the genus description, it differs distinctly from currently known members of Nagumoea. Differences include generally larger (7-29 µm) and more slender (1.0-1.5 µm) valves with acutely rounded apices and 4-5 areolae per stria, a doubly-perforated valvocopula, and the last-formed copula with a highly regular serrated margin. Based on the current knowledge and understanding of the diatom morphology and phylogeny, Anaulus vallus Nikolaev, previously included within the genus Denticula, is transferred to the genus Nagumoea. This brings the current number of the genus members to five. Ecological preferences of Nagumoea are briefly discussed.