Navicula fuxianturriformis sp. nov. (Bacillariophyceae), a new species from southwest China

Abstract

Navicula fuxianturriformis sp. nov., collected from Lake Fuxian, Yunnan Province, China, is described as a new species based on light and scanning electron microscope observations. N. fuxianturriformis sp. nov. has lineolate areolae closed by hymenes internally and a peculiar structure of the raphe system where the raphe is elevated internally on a thin longitudinal rib that is laterally expanded at the central area; features that assign it to the genus Navicula. The key diagnostic features of this new species include: 1) lanceolate valves with the cuneate to apiculate apices, 2) mostly long, slit-like, partly round-rectangular areolae on the valve exterior and round to rectangular areolae internally, 3) external distal raphe fissures that are hooked opposite one another, and 4) the oval-elliptical central area, with two to five pairs of irregularly shortened striae. This combination of features distinguishes N. fuxianturriformis from congers such as N. turriformis, N. turris, N. reinhardtii, N. hoevsgoelreinhardtii, N. mongolreinhardtii, N. apiculatoreinhardtii or N. apiculatoreinhardtii f. biseriata. A discussion of the morphological features of this taxon and morphologically-similar species is presented. These findings increase our understanding about the morphology and distribution of the genus Navicula in China.