Luticola rojkoviensis sp. nov. (Bacillariophyta), a new terrestrial diatom from Central Slovakia

Sampling of fungi in a grassland on a hill in Rojkov, Central Slovakia, revealed a new species of Luticola (Diadesmidaceae). Its terrestrial populations were found close to the basis of the fertile part of the geoglossoid fungi (Geoglossaceae) that were overgrown with filamentous cyanobacteria of the orders Oscillatoriales and Synechococcales. Luticola rojkoviensis sp. nov. is characterized by the valve outline and the structure of the external valve face: valves are weakly dorsiventrally asymmetrical, rhombic-lanceolate in larger cells to rhombic-elliptic and tri-undulate in smaller cells, with shortly protracted and broadly rounded valve apices. Valve face is minimally concave, as the axial area is lowered and the area around distal raphe elevated. The surface of the valve is mostly uneven due to many depressions, so the external shape of the areolae and the impression of irregular longitudinal rows depend on the extent of these valve ornamentations. Proximal raphe endings are unilaterally slightly deflected, expanded into small central pores. The shape of both the proximal and the distal raphe fissures is slightly asymmetrical. The morphological characteristics of Luticola rojkoviensis sp. nov. are remarkably similar to those of L. hustedtii Levkov, Metzeltin et A.Pavlov, L. ectorii Levkov, Metzeltin et A.Pavlov and L. acidoclinata Lange-Bertalot. The association of Luticola rojkoviensis sp. nov. with geoglossoid fungi and epiphytic cyanobacteria is discussed.