Abstract
This paper describes the new species Gomphonema shanghaiensis sp. nov. from Shujiawan River, Shanghai City, in the lower reaches of Yangtze River, China. The description is based on data derived from light and scanning electron microscopy. Valves of Gomphonema shanghaiensis are narrowly lanceolate to rhombic-lanceolate, slightly asymmetrical to the apical axis, with a gibbous central region. The footpole is broadly rounded and the headpole is slightly rostrate to narrowly rounded. The axial area is narrow and linear. Central area is small, and irregularly rectangular in shape. 1–5 rounded external stigmal openings are evident, and internally 1–2 of these are positioned on the central nodule. Striae are slightly radiate at the center, radiate towards the poles. The new species was compared with G. hasta, G. archaevibrio, G. spiculoides, G. stagnorum, G. guaraniarum, G. tumens and G. disgracile, all of which resemble Gomphonema shanghaiensis but differ from the new species in specific details of size, striae density, valve shape and stigmal openings number. This species occurs in relatively clean water in Shanghai.