Two New Benthic Diatoms of the Genus Achnanthidium (Bacillariophyceae) from the Hangang River, Korea

Abstract

Two new benthic freshwater species belonging to the genusAchnanthidiumwere found in Korea.Achnanthidium ovalesp. nov. andA. cavitatumsp. nov. are described as new species based on light and scanning electron microscopy observations and molecular analyses. Both species are compared with the type material of morphologically similar taxa.Achnanthidiumovalediffers from other species belonging to theA.pyrenaicumcomplex in outline, striation pattern, raphe central endings, and freestanding areolae at the apices.Achnanthidiumcavitatumdiffers from other species in theA.minutissimumcomplex in outline, broad axial central area in the raphel ess valve, and slit-like areolae near the axial central area. We assessed their molecular characteristics by analyzing nuclear small subunit (SSU) rRNA and chloroplast-encodedrbcLgene sequences. Both the morphological comparison and the SSU andrbcLsequence analyses provide strong evidence to support the recognition ofA.ovaleandA.cavitatumas new species.