A new Reimeria (Bacillariophyceae) species from lakes Ohrid and Prespa, Macedonia

Ancient lakes are important biodiversity hotspots, including diatom diversity and endemism. Lakes Ohrid and Prespa are no exception and are characterized by a high number of diatom genera and species. Many new species of diatoms have been described from both lakes, occurring in one or both lakes. During observations of the epilithic communities of both lakes, a Reimeria species with morphological characteristics different from those of known species was recorded. This study describes it as a new species Reimeria elliptica based on light and scanning electron microscopy observations. The new species is characterized by small valve size (7.5–20.5 μm long and 3.8–5.0 μm wide), slightly asymmetrical valves with linear-elliptic to elliptic outline and 12–16 striae in 10 μm. A comparison with known Reimeria species based on morphological and ultrastructural characteristics is provided. Reimeria elliptica so far observed only in lakes Prespa and Ohrid.