Three new Gomphonema Ehrenberg (Bacillariophyta, Gomphonemataceae) species from the lower reaches of Yangtze River, China

In this study, three new species of the genus Gomphonema from freshwater lakes of the lower reaches of Yangtze River, China. They include G. qii sp. nov. from Yangcheng Lake, G. poyangense sp. nov. from Poyang Lake, and G. longganense sp. nov. from Longgan Lake, and all of these new species were collected on stone. We detailed morphological features of these new species are described based on light microscopy (LM) and scanning electron microscopy (SEM), and the LM and SEM photographs illustrate the size ranges and particular ultrastructure of these new species. G. qii sp. nov. with clavate-lanceolate valves, bluntly rounded headpole and narrowly-rounded footpole, narrowly axial area, uniseriate striae. G. poyangense sp. nov. with clavate-lanceolate valves, rounded headpole and narrowly-rounded footpole, broadly rhombic-lanceolate axial area, short uniseriate striae, c-shaped to irregularly shaped areolae. G. longganense sp. nov. with slightly heteropolar, linear-lanceolate valves, protruded headpole and rounded footpole, narrowly axial area, variously-shaped areolae. Additionally, three new species only have one stigma per valve. We compare these new species with other similar species of Gomphonema based on valve outline, shape of the axial and center areas, and striae density. While their valve features and symmetry easily assign them to Gomphonema, their differences with 'core' species of the genus are discussed.