Krammer 1985 Category: Asymmetrical biraphid
BASIONYM: Cymbella leptoceros var. rostrata Hustedt 1942
REPORTED AS: Cymbopleura citriformis (Krammer 2003, p. 68, figs 97: 13-15, 98: 1-5) | Cymbopleura designata (Lange-Bertalot and Genkal 1999, p. 226, figs 56: 17-19 INVALID NAME)
GENUS CONSIDERED: Cymbopleura
Contributor: Loren Bahls - September 2015
Length Range: 26-37 µm
Width Range: 9.0-11.6 µm
Striae in 10 µm: 12-14 in the valve center, up to 18 near the apices
Valves are broadly lanceolate and moderately dorsiventral with strongly arched dorsal and ventral margins. Apices are apiculate and extend laterally from the ends of the valve. The axial area is about 1/4 to 1/5 the valve width, curved, and narrower near the apices. The central area is slightly tumid and scarcely wider than the axial area. Raphe branches are weakly lateral near their centers and filiform towards the proximal and distal ends. Proximal raphe ends are slightly expanded and displaced ventrally. Distal raphe ends are comma-shaped and deflected dorsally. Striae are radiate throughout. Areolae in the striae number 26-30 in 10 µm.
The nomenclatural history of this taxon is convoluted. Krammer (1985) proposed that Cymbella leptoceros var. rostrata Hustedt is morphologically dissimilar to Cymbella leptoceros and should, therefore, be elevated to the rank of species, creating the new name and rank of Cymbella designata Krammer. Later, Lange-Bertalot and Genkal (1999) suggested that Cymbella designata belongs in Cymbopleura (p. 226, figs 56: 17-19) but they failed to formally transfer the species, so the name Cymbopleura designata is invalid.
In 2003, Krammer published the new species Cymbopleura citriformis, which appears to be conspecific with Cymbella designata. The type of the basionym Cymbella leptoceros var. rostrata Hustedt 1942, which is Cymbella designata, has nomenclatural priority.
Basionym: Cymbella leptoceros var. rostrata
Author: Hustedt 1942
Length Range: µm
Striae in 10 µm:
Hustedt, F. (1942). Diatomeen aus der Umgebung von Abisko in Schwedisch-Lappland. Archiv für Hydrobiologie 39(1): 87-174 .
Krammer, K. (2002). The genus Cymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 3: 1-584.
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. (1985). Naviculaceae Neue und wenig bekannte Taxa, neue Kombinationen und Synonyme sowie Bemerkungen zu einigen Gattungen. Bibliotheca Diatomologica 9:5-230, 43 pls.
Lange-Bertalot, H. and Genkal, S.I. (1999). Diatoms from Siberia I. Islands in the Arctic Ocean (Yugorsky-Shar Strait). Iconographia Diatomologica 6: 1-292.
Simonsen, R. (1987). Atlas and Catalogue of the Diatom Types of Friedrich Hustedt. J. Cramer, Berlin & Stuttgart 1: 525 pp.
Krammer (2002) reports Cymbella designata from sub-arctic and arctic sites with oligotrophic waters of low mineral content and notes records from north Sweden, north Finland, north Norway, north Russia, Spitsbergen, Greenland, and Alaska. The specimens shown here were collected from small circumneutral tundra lakes above the Arctic Circle in Nunavut, Canada. Cymbella designata (presented as Cymbopleura citriformis) was also reported as a fossil in sediment deposited at the bottom of a lake in north Germany (Krammer 2003).
Red Sand Lake, Nunavut, Canada: home of Cymbella designata.
Credit/Source: Beverly Boynton, Adventurers and Scientists for Conservation.