Krammer 1997 Category: Asymmetrical biraphid
SYNONYM(S): Encyonema gracile Rabenhorst 1853
REPORTED AS: Cymbella lunata (Patrick and Reimer 1975, p. 46, plate 7, figs. 11-14) | Cymbella gracilis (Krammer and Lange-Bertalot 1986, p. 308, fig. 120: 3-5)
Contributor: Loren Bahls - June 2016
Length Range: 19-41 µm
Width Range: 5.5-6.7 µm
Striae in 10 µm: 12-15
Valves are cymbelloid and narrow, with narrowly rounded apices. The dorsal margin is moderately arched. The ventral margin is weakly convex to nearly flat with a slightly tumid central valve. The central area is slightly wider than the axial area,. The raphe is lateral, narrowing near the proximal ends and terminal fissures. Proximal raphe ends are deflected dorsally and terminate in inconspicuous central pores. Distal raphe fissures are long and curved ventrally. Striae on the dorsal side are radiate and more widely separated at the valve center than near the apices. The median dorsal stria has a single isolated areola near the central area. The shorter striae on the ventral side are parallel to radiate near the valve center, becoming convergent near the apices. Areolae in the striae are fine and number 30-35 in 10 µm.
Author: Krammer 1997
Length Range: 16-50 µm
Width Range: 5.5-6.6 µm
Striae in 10 µm: 12-14
Krammer, K. (1997). Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 1. Allgemeines und Encyonema. Bibliotheca Diatomologica 36: 1-382.
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.
Encyonema neogracile is widespread and common in lakes, fens and mossy seeps in the mountains of the Northwest United States. These waters typically have low concentrations of nutrients, low to very low electrical conductance, and circumneutral pH.
Kootenai Pond, Glacier National Park, Montana: home of Encyonema neogracile
Credit/Source: Loren Bahls