Cymbella nanhuaensis sp. nov. (Bacillariophyceae, Cymbellales), a new, enigmatic cymbelloid diatom species from Hunan Province, China | CU Experts

Cymbella nanhuaensis sp. nov. is described as a new freshwater diatom species from epilithic samples collected in Nanhua Stream, Hunan Province, Pearl River Basin, China. The morphological characteristics of the new species are documented in detail based on light and scanning electron microscopy observations. Cymbella nanhuaensis is characterized by slightly dorsiventral, lanceolate valves, the absence of stigmata, and apical pore fields (APFs) that are unequally bisected by distal raphe fissures. Externally, the areolae have rounded openings, whereas internally they are occluded by rounded closing plates. The new species resembles Cymbella orientalis var. delicatula and C. orientalis in APF structure and internal occlusion shape, but can be clearly distinguished by its narrower valve width, distinct valve outline, and higher areolar density. Furthermore, although sharing astigmate valves and bisected APFs with the genus Qinia, C. nanhuaensis differs fundamentally in having rounded external areolar openings and rounded internal closing plates rather than C-shaped or slit-like openings, supporting its placement within Cymbella. This discovery expands our understanding of the morphological diversity and distribution of the genus Cymbella in China.

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