Two new species of Navicula (Bacillariophyta) from Southeast Asia Author Kulikovskiy, Maxim S. K. A. Timiryazev Institute of Plant Physiology RAS, IPP RAS, 35 Botanicheskaya St., Moscow, 127276, Russia max-kulikovsky@yandex.ru Author Chudaev, Dmitry A. Department of Mycology and Algology, Faculty of Biology, M. V. Lomonosov Moscow State University, Leninskie Gory 1, building 12, Moscow, 119234, Russia Author Glushchenko, Anton M. https://orcid.org/0000-0002-2832-1872 K. A. Timiryazev Institute of Plant Physiology RAS, IPP RAS, 35 Botanicheskaya St., Moscow, 127276, Russia Author Kuznetsova, Irina V. K. A. Timiryazev Institute of Plant Physiology RAS, IPP RAS, 35 Botanicheskaya St., Moscow, 127276, Russia Author Kociolek, John Patrick https://orcid.org/0000-0001-9824-7164 Museum of Natural History, Boulder, Colorado, 80309, USA & Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, 80309, USA text PhytoKeys 2022 2022-02-18 190 69 85 http://dx.doi.org/10.3897/phytokeys.190.78164 journal article http://dx.doi.org/10.3897/phytokeys.190.78164 1314-2003-190-69 2460780F0258551EA0D7C380E7D86E92 Navicula winoniformis Chudaev, Glushchenko, Kulikovskiy & Kociolek sp. nov. Figs 1 , 2 Navicula gottlandica sensu Lee, 2012 (fig. 4E) (Algal Flora of Korea vol. 3, num. 8). Holotype. Slide 03572 in collection of Maxim Kulikovskiy at the Herbarium of the Institute of Plant Physiology Russian Academy of Science, Moscow, Russia, represented here by Fig. 1E . Figure 1. A-P Navicula winoniformis Chudaev, Glushchenko, Kulikovskiy & Kociolek, sp. nov. LM, DIC. Size diminution series. Vietnam, slides no 00269 ( A ), 00318 ( L, P, N ), 00323 ( I ), 00326 ( C ), 00328 ( B ), 02079 ( O ), 03572 ( E, F, H, K, M ), 03773 ( D ), 04853 ( J ). Laos, slide no 00956 ( G ). Holotype ( E ). Scale bar: 10 μm . Isotype. Slide MW-D 898s1 in Diatom collection of the Department of Mycology and Algology, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia. Type locality. Vietnam. Khanh Hoa Province, Suối Dầu Reservoir, benthos, 12°09.900'N , 109°03.200'E , 36 m elev., leg. E.S. Gusev, 10.08.2010. Description. LM (Fig. 1A-P ). Valves narrowly lanceolate with rostrate to subcapitate apices, length 29.7-49.0 μm , width 6.5-8.0 μm (n=32). Axial area narrow, slightly widening towards valve centre, central area transversely expanded, with irregular border due to unequal shortening of central striae, usually occupying about 1/2 of valve width. Striae radiate, becoming strongly convergent at the valve ends, 12-14/10 μm . Lineolae easy to resolve in light microscope, 24-27/10 μm . Raphe filiform to narrowly lateral, terminal fissures deflected to the secondary valve side, central pores straight or very slightly deflected to primary valve side, not close standing. SEM, external view (Fig. 2A-C ). Areola openings apically elongate, lying in distinct longitudinal grooves (Fig. 2C , white arrow). Four small isolated areolae with almost circular openings present at valve apices on valve mantle (Fig. 2C , white arrowheads). Raphe-sternum elevated very slightly in valve centre (Fig. 2B , black arrow). Central pores drop-like without any projections, deflected slightly to primary valve side (Fig. 2B , white arrows). Terminal fissures hooked to secondary valve side (Fig. 2A, C , black arrows). Raphe branches with indistinct kink in proximal parts (Fig. 2A , white arrow). Figure 2. A-F Navicula winoniformis Chudaev, Glushchenko, Kulikovskiy & Kociolek, sp. nov. SEM. Sample no 03572. A-C external views D-F internal views A, D the whole valve B, E central area C, F valve end. A black arrows show the terminal raphe fissures. White arrow shows the indistinct kink of raphe branch B white arrows show central raphe pores. Black arrow shows the very slightly elevated raphe-sternum C black arrow shows the terminal raphe fissure. White arrow shows the longitudinal grooves where areola openings are located. White arrowheads show the small isolated apical areolae D white arrows show the accessory rib E black arrow shows the rectangular areola opening. Black arrowhead shows the circular areola opening. White arrows show the central raphe endings. White arrowhead shows the raphe slit F black arrows show the stria which are slightly wider than virgae. White arrow shows the helicroglossa. White arrowheads show the small isolated apical areolae. Scale bars: 5 μm ( A ); 2 μm ( B-E ); 1 μm ( F ). SEM, internal view (Fig. 2D-F ). Striae slightly wider than virgae, lie at same level as latter, no transapical grooves formed (Fig. 2E, F , black arrows). Internal areola openings rectangular (Fig. 2F , black arrow) or circular (near central area) (Fig. 2E , black arrowhead), wider than external ones. Hymenes were not preserved during the material treatment. Four to five small isolated areolae present at each apex (Fig. 2F , white arrowheads). Raphe slit opens obliquely to secondary side and visible in proximal (Fig. 2E , white arrowhead) and distal (Fig. 2F , white arrow) parts only. Raphe-sternum very narrow, widened in centre, separated from accessory rib by longitudinal groove. Accessory rib well-developed (Fig. 2D , white arrows), widened unilaterally in valve centre and at valve apices. Central raphe endings straight, simple, connected by thin indistinct furrow (Fig. 2E , white arrows). Distal raphe endings well-developed helictoglossae deflected to secondary valve side (Fig. 2F , white arrow). Etymology. Specific epithet is given due to similarity of new species to Navicula winona Bahls. Distribution. Vietnam. Type locality (Suối Dầu Reservoir, slide no 03572). Suối Dầu River (slide no 00318, 00323, 03773), Suối Tien River (slide no 00326, 00328), Cai River (slide no 04853), Mư ờng Hoa River (slide no 02079), Da Tien Reservoir (slide 02069). Laos, Nam Lik River (slide no 00956). Ecology. Navicula winoniformis sp. nov. was found in a the reservoirs, and in rivers and waterfalls with different conductivity and pH values (Table 1 ). Below are the dominant species found in the samples along with N. winoniformis sp. nov.: Sample 03572: Neidium gracile Hustedt, Encyonopsis fonticola (Hustedt) Krammer. Sample 00956: Oricymba voronkinae Glushchenko, Kulikovskiy & Kociolek, Pinnularia sikkimensis S.K. Das, C. Radhakrishnan, Kociolek & Karthick, Pinnularia stricta Hustedt, Luticola muticoides (Hustedt) D.G. Mann. Sample 00318: Hydrosera triquetra Wallich, Diadesmis confervacea Kuetzing , Luticola nipkowii (Meister) Glushchenko & Kulikovskiy. Sample 00323: Gomphonema dalatica Glushchenko, Kulikovskiy & Kociolek, Eunotia indosinica Glushchenko & Kulikovskiy. Sample 03773: Eunotia indomalaica Glushchenko, Kulikovskiy & Kociolek, O. voronkinae . Sample 00326: Gomphonema subventricosum Hustedt, D. confervacea , Oricymba perjaponica (Krammer & Lange-Bertalot) Kulikovskiy, Glushchenko & Kociolek, Rhopalodia gibba (Ehrenberg) O. Mueller , Encyonema javanicum (Hustedt) D.G. Mann. Sample 00328: Placoneis paraundulata T. Ohtsuka, E. javanicum , Eunotia laoarcus Glushchenko, Kulikovskiy & Kociolek. Sample 04853: D. confervacea , Platessa oblongella ( Ostrup ) Wetzel, Lange- Bertalot & Ector, Luticola taylorii Levkov, Metzeltin & Pavlov, N. gracile , E. javanicum , O. voronkinae , Frustulia magaliesmontana Cholnoky. Sample 02079: P. oblongella , Reimeria sinuata (Gregory) Kociolek & Stoermer, E. javanicum , Encyonema leei Krammer. Sample 00269: G. dalatica , Adlafia lamdongiensis Glushchenko, Kulikovskiy & Kociolek, Kobayasiella lamii Glushchenko, Kulikovskiy & Kociolek.