Four new species from the diatom (Bacillariophyceae) genus Adlafia Moser, Lange-Bertalot & Metzeltin from waterbodies of Vietnam Author Glushchenko, Anton M. K. A. Timiryazev Institute of Plant Physiology RAS, IPP RAS, 35 Botanicheskaya St., Moscow, 127276, Russia https://orcid.org/0000-0002-2832-1872 gluschenkoam@studklg.ru Author Kociolek, John Patrick Museum of Natural History, Boulder, Colorado, USA & Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, 80309, USA https://orcid.org/0000-0001-9824-7164 Author Kuznetsova, Irina V. K. A. Timiryazev Institute of Plant Physiology RAS, IPP RAS, 35 Botanicheskaya St., Moscow, 127276, Russia Author Kulikovskiy, Maxim S. K. A. Timiryazev Institute of Plant Physiology RAS, IPP RAS, 35 Botanicheskaya St., Moscow, 127276, Russia text PhytoKeys 2020 162 13 27 http://dx.doi.org/10.3897/phytokeys.162.57657 journal article http://dx.doi.org/10.3897/phytokeys.162.57657 1314-2003-162-13 C6BEE9C7C57D5E7EAE2E335EEEADD57E Adlafia lamdongiensis Glushch., Kulik. & Kociolek sp. nov. Figs 1 , 2 Holotype. Slide no. 00269 in collection of Maxim Kulikovskiy at the Herbarium of the Institute of Plant Physiology Russian Academy of Science, Moscow, Russia, represented here by Fig. 1A . Figure 1. A-G Adlafia lamdongiensis Glushch., Kulik. & Kociolek sp. nov. LM, DIC, size diminution series. Slides no 00269 ( A-C, E-G ) and 03593 ( D ). Holotype ( A ). Scale bar: 10 μm . Type locality. Vietnam. Lam Đ ồng Province, Da Tien Reservoir, benthos, 11°58.816'N , 108°26.987'E , 1503 m elev., leg. E.S. Gusev, 21.06.2012 . Description. LM (Fig. 1A-G ). Valves linear with weakly convex margins. Ends are distinctly narrowly-rostrate. Length 9.7-13 μm (11.4 +/- 0.9; n = 16), breadth 2.5-2.8 (2.7 +/- 0.1; n = 16) μm . Striae and areolae not resolved in LM. SEM, external view (Fig. 2A-C ). Valve face flat. Axial area linear. Central area absent. Raphe filiform, weakly lateral. Proximal raphe endings slightly expanded. Distal raphe endings positioned on valve mantle, hooked and curved in same direction, terminating at valve face-mantle junction. Striae uniseriate, radiate, becoming abruptly convergent approaching apices, Striae 45-50 in 10 μm (47.5 +/- 1; n = 16). Areolae rounded or rectangular, hymenes not preserved during specimen preparation. Slit-like opening of apical areolae arranged in one row onto valve apex. Areolae 40-50 in 10 μm (45 +/- 1.8; n = 16). SEM, internal view (Fig. 2D-F ). Raphe slightly lateral, lies in a prominent and raised raphe-sternum. Proximal raphe endings deflected towards primary side of valve. Distal raphe endings terminating in small helictoglossae. Striae continuing onto valve mantle. Short striae alternate with longer striae at valve center. Areolae rounded or rectangular. Openings of apical areolae apically elongated. Figure 2. A-F Adlafia lamdongiensis Glushch., Kulik. & Kociolek sp. nov. SEM. Sample no 00269 A-C external views D-F internal views A whole valve. The valve face is flat B central area C valve end D whole valve E central area F valve end. Scale bars: 2 μm ( A ), 1 μm ( D ), 0.5 μm ( B, C, E, F ). Etymology. Epithet refers to the province of Vietnam ( Lam Đ ồng Province) where the specimens were found. Distribution. Vietnam. Type locality (slide no. 00269) and slide no. 03593.