Description

Morphological description. The frustule is drum-shaped, the valve is flat or slightly concave or convex (Fig. 3 D-H). Valve diameter 13.6 - 26.2 μm, height 3.4 - 5.2 μm. Areolae are arranged into sectors. The external openings of the process (4 - 6) are clearly visible on the curved outer surface the mantle (Fig. 3 F, H). The pseudonodulus is located above the openings of the rimoportulae, it has a slight depression. According to Hasle (1977), there are no significant taxonomic differences between A. normanii f. subsalsus and the nominate form (the ranges of valve diameters coincide), but there may be ecological preferences. Krammer and Lange-Bertalot (2000) did not identify forms, but gave so-called morphotypes that do not have a rank in nomenclature and, according to their data, in the A. normanii population from the Rhine region, a continuous range of forms was observed during the life cycle. Kozyrenko et al. (2008) synonymized A. normanii f. subsalsus with the nominate form and we adhere to their point of view.

Common Names

Taxonomic Hierarchy

Kingdom: Chromista

Phylum: Ochrophyta

Class: Bacillariophyceae

Order: Coscinodiscales

Family: Hemidiscaceae

Genus: Actinocyclus

Species: Actinocyclus normanii