Krammer 2003 Category: Asymmetrical biraphid
BASIONYM: Cymbopleura elliptica Krammer 2003
REPORTED AS: Cymbella hybrida (Krammer and Lange-Bertalot 1986, p. 337, plate 145, fig. 2 [not figs 1 or 3]) | Cymbopleura hybrida var. capitata (Krammer 2003, p. 63, figs 87:5-14) | Cymbopleura hybrida (Diatoms of the US)
Contributor: Loren Bahls -
Length Range: 38-49 µm
Width Range: 10.8-11.9 µm
Striae in 10 µm: 10-13 at the valve center, 15-16 near the apices
Valves are linear-elliptic and slightly dorsiventral, with barely convex dorsal and ventral margins and abruptly constricted subcapitate to capitate apices. The axial area is relatively narrow, 2-3 times wider than the raphe. The central area is large and transversely oval or rectangular. The raphe is lateral, becoming filiform near the proximal ends. Proximal raphe ends have small hooks deflected towards the ventral margin. Distal raphe fissures are deflected dorsally. Striae are parallel at the valve center and radiate towards the apices. Areolae are difficult to resolve in LM and number 28-34 in 10 µm.
This taxon overlaps in size and structure with Cymbopleura hybrida var. capitata and its basionym Cymbella hybrida var. capitata and is indistinguishable from them for all practical purposes. It’s affinity with Cymbopleura hybrida is weak and it should be treated as a species in its own right.
Basionym: Cymbopleura elliptica
Author: Krammer 2003
Length Range: 30-44 µm
Width Range: 8.0-11.5 µm
Striae in 10 µm: 10-13 at the valve center, up to 18 at the ends
Valves barely dorsiventral, broadly linear to broadly subelliptical, dorsal and ventral margins straight or barely convex, ends narrowly capitate with broad shoulders. Length 30-44 µm, breadth 8-11.5 µm, maximum length/breadth ratio 4.4. Axial area narrow, linear, almost in the median line of the valve. Central area large, more than 1/2 the valve breadth, rhomboid or something irregular, sometimes asymmetrical. Raphe slightly lateral, narrowing towards the distal and proximal ends. Proximal raphe ends distinctly expanded, the outer raphe fissure somewhat ventrally tipped (Fig. 89: 17a); terminal fissures dorsally deflected. Striae radiate throughout, indistinctly punctate. Striae in the middle portion (dorsal) 10-13/10 µm, up to 18/10 µm towards the ends, puncta 30-32/10 µm.
Fontell, C.W. (1917). Süsswasserdiatomeen Ober-Jämtland in Schweden. Arkiv för Botanik 14(21): 1-68.
Krammer, K. (2003). Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 4: 1-530.
Krammer, K. and Lange-Bertalot, H. (1986). Bacillariophyceae. 1. Teil: Naviculaceae. In: Ettl, H., J. Gerloff, H. Heynig and D. Mollenhauer (eds.) Susswasserflora von Mitteleuropa, Band 2/1. Gustav Fisher Verlag, Jena. 876 pp.
Cymbopleura elliptica is uncommon in lakes and ponds of the northern Rocky Mountains, where it prefers cold, oligotrophic, circumneutral waters (pH range: 6.80-7.77) with low to moderate levels of dissolved solids (specific conductance range: 53-250 µS/cm).
Lake McDonald, Glacier National Park, Montana: home of Cymbopleura elliptica.
Credit/Source: National Park Service webcam
Images on this taxon page were previously included under a broad circumscription of Cymbopleura hybrida. As of this date, C. elliptica is presented as a unique biological species distinct from C. hybrida. - S. Spaulding and L. Bahls