Diploneis Guide
Credit: Ditmar Metzeltin
  1. Valves elliptic to panduriform
  2. Longitudinal canals present
  3. Areolae complex

Frustules of Diploneis are typically elliptic to panduriform, with bluntly rounded apices. Each valve possesses two longitudinal canals, one on each side of the raphe. The canals are positioned within the silica cell wall and open to the exterior through pores, but lack openings to the interior of the cell. The function of these canals is uncertain. The frustules are often heavily silicified, with complex (loculate) areolae.

The genus Diploneis is large and diverse, with most species primarily from epipelic habitats.

Recent publications clarify a unique set of freshwater species and unappreciated diversity of species in the genus Diploneis (Jovanoska 2015, Kulikovsky et al. 2015, Lange-Bertalot and Fuhrmann 2016, 2017). These works challenge the long-standing mindset that Diploneis is primarily a marine genus with few freshwater representatives. While the freshwater species may be both infrequent and not abundant (Lange-Bertalot and Fuhrmann 2017), there is a much larger species richness in oligotrophic waters. Furthermore, these authors point out that European rivers have been so altered by nutrients and other pollutants that many species of Diploneis are simply not encountered in modern surveys. When species of Diploneis are encountered in surveys, they are few in number and they are often overlooked. This situation is certainly the case in North America, where a number of taxa have not been identified in regional surveys.