Rabenhorst 1853 Category: Asymmetrical biraphid
BASIONYM: Encyonema auerswaldii Rabenhorst 1853
SYNONYM(S): Encyonema caespitosum var. auerswaldii (Rabenhorst) van Heurck 1882 | Cymbella ventricosa var. auerswaldii (Rabenhorst) Meister 1912 | Cymbella caespitosum var. auerswaldii (Rabenhorst) Cleve-Euler 1955
Contributor: Rex Lowe - January 2015
Length Range: 23-33 µm
Striae in 10 µm: 10-12 in the center of the valve, 12-15 near the ends
Valves are strongly arched dorsally and slightly tumid ventrally, with rounded ends. In larger specimens, the ends may be slightly rostrate. Dorsal striae are parallel near the center, becoming radiate near the ends. Ventral striae are slightly radiate. Areolae in each stria are clearly visible and number approximately 25 in 10 µm. The axial area is slightly lanceolate; it is narrow near the ends and slightly expanded and rounded in the central area. The raphe is broad and lateral. The proximal raphe ends are dorsally deflected, while the distal raphe ends are ventrally deflected.
Living cells form mucilage tubes, where they live as colonies inside the tubes.
The lectotype of E. auerswaldii was examined and compared to types of E. prostratum and E. cespitosum (Silva et al. 2013). They report that specimens of E. prostratum are broader than E. cespitosum (16–24.7 μm versus 9.6–12 μm). The maximum length of E. prostratum was reported as 88 μm, and the maximum length of E. cespitosum was reported as 47 μm.
Basionym: Encyonema auerswaldii
Author: Rabenhorst 1853
Length Range: 30 µm
Striae in 10 µm: 11-12
Meister, F. (1912). Die Kieselalgen der Schweiz. Beiträge zur Kryptogamenflora der Schweiz, 4/1, 1–254.
Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.
Rabenhorst, L. (1853). Die Süßwasser-Diatomaceen (Bacillarien) für Freunde der Mikroskopie. Leipzig, 72 pp.
Silva, W.J., Jahn, R., Ludwig, T.A.V. and Menezes, M. (2013). Typification of seven species of Encyonema and characterization of Encyonema leibleinii comb. nov. Fottea, Olomouc 13(2): 119–132.
Encyonema auerswaldii often grows as an epiphyte. It forms long, branching mucilage tubes. Encyonema auerswaldii is common in freshwaters across the US.
Periphyton from the Eel River, California, showing Encyonema auerswaldii attached to the green alga, Cladophora.
Credit/Source: R. Lowe