Observation on Achnanthes Bory sensu stricto (Bacillariophyceae) from subaerial habitats in Macedonia and comparison with the type material of A. coarctata (Brebisson ex W. Smith) Grunow, A. coarctata var. sinaensis Hustedt and A. intermedia Kutzing
Observation on Achnanthes Bory sensu stricto (Bacillariophyceae) from subaerial habitats in Macedonia and comparison with the type material of A. coarctata (BréBisson ex W. smith) Grunow, A. coarctata var. sinaensis hustedt and A. intermedia KützinG Abstract: Four species of Achnanthes sensu stricto have been observed in several subaerial habitats/localities in Macedonia. The morphological features of all recorded species have been described based on light and scanning electron microscope
... on microscope observations. Two species posses similar morphological features as already described species and were identified as A. coarctata (BréBisson ex W. smiTh) GrunoW and A. sinaensis (husTedT) stat. nov. Two species have unique set of characters that separate them from the known species and are described in this study as A. pseudocoarctata levkov et Tofilovska sp. nov. and A. prominula levkov et Tofilovska sp. nov. All recorded species were compared with the type populations including A. coarctata, A. coarctata var. sinaensis husTedT, and A. intermedia küTzinG. Observations of the syntype populations of A. coarctata give precise frame of the morphological variability of the species. Achnanthes pseudocoarctata appears similar to A. coarctata, but can be easily differentiated by the morphological and ultrastructural features of the rapheless valve. Achnanthes coarctata var. sinaensis has distinct morphological characters that make clear separation from A. coarctata, and therefore we propose a new status of this taxon with raising its rank to a species level. Achnanthes prominula appears similar to A. intermedia, but from latter can be easily separated by the position of the rapheless sternum. From other species with lanceolate or elliptic-lanceolate valves, A. prominula can be differentiated by the valve shape, position of the rapheless sternum, central area, stria and areola density.