Krammer 1997 Category: Asymmetrical biraphid
BASIONYM: Encyonema pergracile Krammer 1997
Valves are elongate, linear-lanceolate and dorsiventral. The apices are narrow and acute, slightly deflected toward ventral side in larger specimens. The raphe is lateral with external proximal ends that are slightly dorsally deflected before the distal ventral deflection. Internally, the raphe appears to be continuous through the central area. The distal raphe has relatively long terminal fissures, that is, the helictoglossae are distantly spaced from each valve apex. The axial area is linear and slightly expanded at the central area. A single isolated punctum is present on the dorsal side of the central area, in line with a central stria. The external expression of the punctum is small and circular, while the internal expression is elongate and opposite a bifurcate cleft in the intermissio. Striae are slightly radiate becoming convergent near the apices. This is most apparent on the ventral side of the valve as the stria density increases. Striae are uniseriate and composed of transapically elongated areolae.
The specimens shown here appear to align most closely with E. pergracile, although they are more narrow (6.5-7.8) than the specimens described by Krammer (1997).
This taxon is part of a large, diverse species complex (Krammer 1997). It includes both Cymbella gracilis (Ehrenberg) Kützing and C. gracilis (Rabenhorst) Cleve. It appears that the type of Cymbella gracilis is ambiguous, and that the name is poorly circumscribed. Further investigation may show additional North American species.
Basionym: Encyonema pergracile
Author: Krammer 1997
Length Range: 27-57 µm
Width Range: 8-9.2 µm
Striae in 10 µm: 10-14
Cite This Page:
Spaulding, S., and Bishop, I. (2014). Encyonema pergracile. In Diatoms of the United States. Retrieved April 26, 2017, from http://westerndiatoms.colorado.edu/taxa/species/encyonema_pergracile
Species: Encyonema pergracile
Greville, R.K. (1855). Report on a collection of Diatomaceae made in the district of Braemar by Professor Balfour and Mr. Gerge Lawson. Annals and Magazine of Natural History, 2nd series, 15:252-261.
Krammer, K. (1997). Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 1. Allgemeines und Encyonema. Bibliotheca Diatomologica 36: 1-382.
Van Heurck, H. (1896). A Treatise on the Diatomaceae. Translated by W.E. Baxter. William Wesley & Son, London. 558 pp., 35 pls.
Encyonema pergracile was described from from Norway, but was also verified and illustrated from samples in Florida (Krammer 1997). It was found occasionally in rivers in the Sierra Nevada mountains of California (Spaulding, US Geological Survey, NAWQA survey 2012).
This page originally appeared March 2, 2015 with the name Encyonema neogracile. These specimens appear to be more closely aligned with E. pergracile because of the length and width. These specimens, however, are smaller than E. pergracile (8-9.2) as given in the original description of Krammer (1997).