Valves are weakly arcuate, with rounded ends. Both ventral and dorsal margins are distinctly sinuate, with undulations occurring 2 in 10 µm. Undulation of the central margin is bilateral, while more dorsal and ventral undulations toward the apices are alternate. Breadth in the center of valve is 8.7-11.6 µm at undulations (widest part), 6.3-8.0 µm between undulations (narrow parts), and 3.7-5.4 µm at the ends. Striae are interrupted by a sternum near the ventral margin. Areolae are visible in LM, numbering 21-27 in 10 µm. The raphe is short and curves onto the ventral mantle, near the apices.
While many authors continue to use the name Amphicampa eruca, Brightwell (1859) elevated A. eruca Ehrenberg 1954 from Ehrenburg’s subdivision of Eunotia, Amphicampa, to the genus level Eunotia eruca. Two years later A. eruca was superfluously synonymized with A. miriabilis Eherenberg ex Ralfs in Pritchard 1861. Furthermore, Boyer (1927) lectotypified A. eruca for the genus Amphicampa, which was later re-lectotypified to A. mirabilis (Farr et al. 1979). Here we recognize the current valid name of this taxon as Eunotia eruca (Ehrenberg) Brightwell 1959, however since there is no consensus on recognition of the genus Amphicampa (as Amphicampa, Patrick and Reimer 1966, Kociolek 2000; as Eunotia, Krammer and Lange-Bertalot 1991; and awaiting detailed analysis, Round et al. 1990, Williams and Reid 2006). The few taxa recognized in the genus have a reduced raphe system and a sinuate ventral valve margin. Further work should be conducted to treat this species, as the classification in the Eunotiophycidae is in flux.
Basionym: Amphicampa eruca
Author: Ehrenberg 1854
Length Range: µm
Striae in 10 µm:
Collins, G.B. (1968). Implications of diatom succession in postglacial sediments from two sites in northern Iowa. Ph.D. dissertation, Iowa State University.
Ehrenberg, C.G. (1854). Mikrogeologie. Einundvierzig Tafeln mit über viertausend grossentheils colorirten Figuren, Gezeichnet vom Verfasser. Voss, Leipzig., Pl. 5, II, fig. 23 (iconotype).
Elmore, C.J. (1921). The Diatoms (Bacillarioideae) of Nebraska. Ph.D. dissertation, University of Nebraska, Lincoln, 215 pp.
Kociolek, J.P. (2000). Valve ultrastructure of some Eunotiaceae (Bacillariophyceae), with comments on the evolution of the raphe system. Proc. Calif. Acad. Sci. Occasional Proceed., 4th series, 52: 11-21.
Krammer, K. and Lange-Bertalot, H. (1991). Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. In Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.). Süsswasserflora von Mitteleuropa. 2(3): 1-576. Gustav Fisher Verlag, Stuttgart, Germany.
Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.
Pritchard, A. (1861). A history of infusoria, living and fossil. Edition IV, Whittaker & Co., London, 968 pp.
Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.
Williams, D.M. and Reid, G. (2006). Amphorotia nov. gen., a new genus in the family Eunotiaceae (Bacillariophyceae) based on Eunotia clevei Grunow in Cleve et Grunow. Diatom Monographs, Vol. 6. A.R.G. Verlag K.G., 153 pp.
Williams, D.M. and Reid, G. (2006). Fossils and the tropics, the Eunotiaceae (Bacillariophyta) expanded: A new genus for the Upper Eocene fossil diatom Eunotia reedii and the recent tropical marine diatom Amphora reichardtiana. European Journal of Phycology 41(20): 147-154. 10.1080/09670260600628564
Amphicampa eruca was originally described from a fossil deposit in Mexico (Ehrenberg 1854). Modern collections are found in disparate localities including the San Joaquin River in California (Elmore 1921 [as Eunotia eruca, Patrick and Reimer 1966 [as A. mirabilis], Kociolek 2000), and subfossil deposits in prairie potholes (Collins 1968, M. Julius, unpublished).
Distribution in rivers of the continental U.S. based on the National Water Quality Assessment program. Retrieved 26 July 2016.
Credit/Source: USGS BioData