Sovereign 1958 Category: Symmetrical biraphid
BASIONYM: Navicula walkerii Sovereign 1958
Contributor: Loren Bahls - November 2011
Length Range: 114-154 µm
Width Range: 24-28 µm
Striae in 10 µm: 9-10
Valves are lanceolate to somewhat rhombic-lanceolate with obtuse, rounded ends. The axial area is barely wider than the raphe at the ends, then widens to three times the width of the raphe near the central area. The central area is rounded and slightly asymmetrical, somewhat shallower on the secondary side than on the primary side of the valve. The raphe is lateral, becoming filiform near the central area, where the proximal ends are hooked toward the secondary side. Striae are radiate throughout most of the valve, becoming parallel and finally somewhat convergent near the ends. Striae are crossed by longitudinal lines, formed by the margin of an internal axial plate. Voigt discontinuities are clearly evident on the secondary side. The areolae are easily distinguished and number about 20 in 10 µm.
Basionym: Navicula walkerii
Author: Sovereign 1958
Length Range: 108-194 µm
Width Range: 22-29 µm
Striae in 10 µm: 9
Valvae rhomboideo-lanceolatae apicibus obtuse rotundatis, non protractis, 108-194 microns longae, 22-29 microns latae. Rhaphe directa, filiformis, poris centralibus internis in eandem partem flexis, fissuris terminalibus longis in eandem partem curvatis. Area axialis modice lata, lanceolata, irregulariter definita, area centralis lata suborbicularis. Costae transapicales circiter 9 in 10 microns, radiantes, prope apices ad lineam mediam perpendiculares, intervalla cum membrana exteriore lineolata, lineolis circiter 20 in 10 microns, in membrana inferiore cum poro elongata juxta marginem.
Kociolek, J.P., Spaulding, S.A. and Kingston, J.C. (1998). Valve morphology and systematic position of Navicula walkeri (Bacillariophyceae), a diatom endemic to Oregon and California (USA). Nova Hedwigia 67: 235-245.
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.
Sovereign, H.E. (1958). The diatoms of Crater Lake, Oregon. Transactions of the American Microscopical Society 77(2):96-134.
Navicula walkeri is an endemic species of the Pacific Northwest, so far reported only from Oregon and California. The type locality is a bay on Wizard Island, Crater Lake National Park. Sovereign (1958) also reports this species as present in nearby Emerald Pool and Diamond Lake, in Spring Creek, Klamath County, Oregon, and as an upper Pliocene fossil in the Terrebonne diatomite beds in northern Oregon. There are three records for Navicula walkeri in the Montana Diatom Collection, all from streams in Oregon, where it prefers circumneutral water with very low concentrations of dissolved solids.
Snow Creek, Deschutes County, Oregon, home of Navicula walkeri
Credit/Source: U.S. Forest Service photo