Lowe & Sherwood 2009 Category: Monoraphid
BASIONYM: Achnanthes tumescens Lowe & Sherwood 2009
Contributor: Rex Lowe - December 2011
Length Range: 29-37 µm
Width Range: 8.0-9.5 µm
Striae in 10 µm: 14-15 on raphe valve, 12-13 on rapheless valve
Valves are linear-lanceolate, gibbous in the center valve, with broadly rounded ends.The raphe valve has a narrow axial area and a nearly rectangular central area extending to the valve margins. The proximal raphe ends are deflected slightly in one direction, with the distal ends curved strongly toward the mantle in the opposite direction. The axial on the rapheless valve is positioned near the valve margin. Striae are punctate and slightly radiate on raphe valve and parallel in the center. Striae on the rapheless valve are slightly radiate and curved near the apices.
Basionym: Achnanthes tumescens
Author: Lowe & Sherwood 2009
Length Range: 22.0-36.5 µm
Width Range: 6.5-8.5 µm
Striae in 10 µm: 15-17
Valves linear-lanceolate, swollen in the center, with broadly rounded ends, 22.0-36.5 µm long, 6.5-8.5 µm wide. Raphe valve with narrow axial area and a nearly rectangular central area extending to the valve margins (Figs 20-23). Raphe with proximal ends deflected slightly in one direction, with distal ends curved strongly towards mantle in opposite direction. Rapheless valve with axial area near valve margin (Figs 24-26). Striae punctate, slightly radiate on raphe valve (Figs 27, 28) on rapheless valve parallel in center, becoming slightly radiate with respect to the axial area, curved at the ends (Figs 29, 30), 15-17 in 10 µm on both valves. Puncta 16 in 10 µm on both valves.
Lowe, R.L., Sherwood, A.R. and Ress, J.R. (2009). Freshwater species of Achnanthes Bory from Hawai'i. Diatom Research 24(2): 327-340.
Achnanthes tumescens was the most abundant and widely distributed species in collections from subaerial well walls of the Hawaiian islands of Oahu and Maui. It co-occurred with Pinnularia borealis, Hantzschia amphioxys and Diadesmis spp.