We present light and scanning electron microscopical observations on two new species of Navicula Bory sensu stricto from Southeast Asia. Naviculawinoniformis Chudaev, Glushchenko, Kulikovskiy & Kociolek, sp. nov. differs from taxa with similar outline and size by the combination of simple drop-like external raphe endings deflected to the primary valve side, presence of well-developed external longitudinal grooves and relatively low lineolae density. Naviculasparsilineolata Chudaev, Glushchenko, Kulikovskiy & Kociolek, sp. nov. can be discriminated from the taxa of similar valve shape and size by consistently lower lineolae density, and from the majority of them also by the structure of external proximal raphe endings with small projections in proximal parts and larger triangular insertions in distal parts. Some remarks on Navicula species diversity and its distribution in the Southeast Asia are given.
Keywords: Diatoms; Navicula; Southeast Asia; distribution; freshwaters; morphology; new species; taxonomy.
Maxim S. Kulikovskiy, Dmitry A. Chudaev, Anton M. Glushchenko, Irina V. Kuznetsova, John Patrick Kociolek.