Guide to Nupela

Species of Nupela are small in size, generally less than 20 µm. Although the genus was first described as being isovalvar, many recently described species have been found to be heterovalvar in regard to raphe development. Heterovalvar species have one valve with a fully developed raphe and the other valve with a reduced, or absent raphe. The valves of Nupela are slightly asymmetric to the apical axis and the central area is asymmetric. The central area may extend nearly to the valve margin. Areolae are elliptic, elongated in the transapical axis. The areolae are covered by hymenes, although note that in many SEM images the thin silica of the hymenes is not preserved. A distinctive feature of Nupela appears to be that the external openings of the areolae are larger than the internal openings. The areolae are arranged in striae of variable length. The striae appear as narrow, longitudinal bands. These longitudinal bands number from 2 to 4, and may be variable in number between sides of the raphe of the same valve. The external proximal raphe is slightly expanded. The internal proximal raphe is somewhat curved. Some taxa have T-shaped proximal raphe ends.

Nupela was originally described from from high elevation ponds of Papua New Guinea. Since its initial discovery, Nupela has been reported across Europe, South America, North America, Asia and Africa in neutral pH, low conductivity waters.