Two new species of the diatom genus Navicula Bory (Bacillariophyceae) from Vietnam (Southeast Asia)

We present light and scanning electron microscopical observations on two new species of Navicula Bory sensu stricto from Vietnam. These new species, Navicula babeiensis Chudaev, Glushchenko, Kulikovskiy & Kociolek sp. nov. and Navicula pseudokuseliana Chudaev, Glushchenko, Kulikovskiy & Kociolek sp. nov. are described and distinguished from others in the genus on the basis of valve outline and shape of the apices, as well as stria and areola densities. These species possess all the typical morphological features for the genus, including uniseriate lineolate striae covered by internal convex hymenes, median raphe with accessory rib, and external distal raphe ends that are hooked in the characteristic way for the genus. Comparisons with similar taxa are given. Our new data extend the information about the diversity of diatoms in general and for Navicula taxa specifically, in Southeast Asia.