Lowe and Sherwood 2009 Category: Monoraphid
BASIONYM: Achnanthes undulorostrata Lowe and 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 triundulate, with broadly rounded ends. The raphe valve has a narrow axial area and a nearly rectangular central area extending to the valve margins. The raphe is externally sinuous, with proximal ends deflected slightly in one direction and distal ends curved strongly towards mantle in the opposite direction. The rapheless valve has an axial area near the valve margin. Striae are punctate and radiate throughout on the raphe valve. On the rapheless valve, the striae are parallel in the center, becoming radiate with respect to the axial area then becoming slightly to strongly curved at the ends.
Basionym: Achnanthes undulorostrata
Author: Lowe and Sherwood 2009
Length Range: 30.5-35.5 µm
Width Range: 8.0-9.5 µm
Striae in 10 µm: 14-15 in 10 µm on raphe valve, 12-13 in 10 µm on rapheless valve
Valves triundulate with broadly rounded ends, 30.5-35.5 µm long, 8.0-9.5 µm wide. Raphe valve with narrow axial area and a nearly rectangular central area extending to the valve margins. Raphe externally sinuous, with proximal ends deflected slightly in one direction, with distal ends curved strongly towards mantle in opposite direction (Fig. 63). Internal raphe slits with proximal ends slightly deflected to one side (Fig. 64). Rapheless valve with axial area near valve margin. Striae punctate, radiate throughout on raphe valve (Figs 55¬-58), on rapheless valve parallel in the center, becoming radiate with respect to the axial area, slightly to strongly curved at the ends (Figs 59-62, 65-66), 14-15 in 10 µm on raphe valve, 12-13 in 10 µm on rapheless valve. Intemal costae separating striae, wíth oblique ridges in rapheless valve resulting in a spiral pattern visible in SEM (Fig. 66). 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 undulorostrata was described from the island of Maui, Hawaii. It was also found in collections from Oahu. This taxon occurs in relatively dry sites in association with A. tumescens, Pinnularia borealis, Diadesmis spp. and Cosmioneis spp.