Valve ultrastructure of two species of the diatom genus Gomphonema Ehrenberg (Bacillariophyta) from Yunnan Province, China

We describe valve ultrastructure of two species of the freshwater diatom genus Gomphonema from a stream and Lugu Lake in Yunnan Province, China, and describe one of these two species as new to Science. Gomphonema emines Skuja was described over 80 years ago. This large, multistigmate species has uniseriate striae without occlusions, large pseudosepta and septa, and internal stigma openings that are round, positioned within ellipsoidal depressions on the extended central nodule. In these features it is distinguished from most of the 'typical' species of the genus. Gomphonema yunnaniana Y.Liu et Kociolek sp. nov. has biseriate striae without occlusions, a large, round external stigma opening and an internal stigma opening that is elevated and contained within a lip-like structure. In these features it is distinguished from the 'typical' species of the genus. We compare these two putatively endemic species from Yunnan with other species groups of the genus.