Placoneis jovanovskiana sp. nov. (Bacillariophyceae), a new species from Lake Tanganyika, East Africa

Placoneis is a genus of symmetric biraphid diatoms in the family Cymbellaceae (order Cymbellales). Morphologically, they are characterized by a linear to lanceolate valve outline, occasionally featuring rostrate or capitate ends. The areolae are loculate and arranged in uniseriate striae within a narrow axial area, and the proximal raphe ends are straight with slight external expansions. Although a limited number of Placoneis species have been documented in Lake Tanganyika, morphologically similar taxa have been reported from South Africa. Here, based on observations using light microscopy (LM) and scanning electron microscopy (SEM), we describe a new species, Placoneis jovanovskiana sp. nov., identified in modern assemblages from the southern basin and a tributary of Lake Tanganyika. Morphologically, the species resembles Placoneis exigua, Placoneis amphibola, Placoneis clementis, Paraplaconeis placentula, and Geissleria decussis, but differs significantly in valve dimensions, valve outline, central area, apical shape, and striae density and orientation.