(Grunow) Wetzel and Van de Vijver 2015 Category: Symmetrical biraphid
BASIONYM: Navicula atomoides Grunow 1880
SYNONYM(S): Navicula minima var. atomoides (Grunow) Cleve
REPORTED AS: Navicula tantula (Hustedt 1934, pl. 399, figs 54-57) | Eolimna minima (Moser et al. 1998, vol. 38, pg. 153) | Eolimna tantula (Werum and Lange-Bertalot 2004, pg. 147, pl. 39, figs 8, 9; pl. 40, fig. 1)
Contributor: Alison Minerovic - May 2016
Length Range: 5-15 µm
Width Range: 2.6-3.5 µm
Striae in 10 µm: 30-36
Valves are small, linear to linear-elliptic with broadly rounded apices. The axial area is narrow, widening slightly toward the central area. The central area is distinctly rectangular or bow tie-shaped, with one areola of each stria extending onto the shallow mantle. The raphe is filiform, with proximal ends slightly ‘tear-drop’ shaped. Distal raphe ends are deflected to same side, terminating internally in small helictoglossae. Striae are radiate, uniseriate, and noticeably curved near the central area. Areolae are occluded internally. Polar bars are absent, but large apical perforations are present and occluded internally.
There has been much confusion regarding the taxonomic identity of Sellaphora atomoides and related species. The recent treatment of the former Eolimna minima and Sellaphora seminulum species complexes are further explained in Wetzel et al. (2015), and the specimens illustrated here appear to agree with the treatment of S. atomoides described by the Wetzel et al.
Basionym: Navicula atomoides
Author: Grunow 1880
Length Range: 8 µm
Width Range: 4 µm
Striae in 10 µm: 27-30
Van Heurck, H. (1880). Synopsis des Diatomées de Belgique. Atlas. Ducaju & Cie., Anvers.
Wetzel, C.E., Ector, L., Van de Vijver, B., Compère, P. and Mann, D.G. (2015). Morphology, typification and critical analysis of some ecologically important small naviculoid species (Bacillariophyta). Fottea, Olomouc 15(2): 203–234. 10.5507/fot.2015.020
Sellaphora atomoides has been verified from aerial habitats and ‘pristine’ conditions. The taxonomic treatment and autecology of S. atomoides is very recent and has likely been reported under different names in the past, including Eolimna minima, Eolimna tantula, and Sellaphora seminulum. Because small-celled naviculoid taxa are often dominant in benthic freshwater communities, they are considered ecologically important taxa and in need of revision and further scrutiny. The recent treatment by Wetzel et al. (2015) will aid in clarifying the habitat preferences and distribution of S. atomoides and related taxa.