Abstract
The diatom genus Entomoneis has a species with unique morphology. Entomoneis has a series of unique features such as connecting lines with different shapes, sigmoid raphe on the bilobate keel, different curtains, and multiple girdle bands. Most species belonging to this genus are found in marine and saline habitats. In fact, the genus Entomoneis is an epicalic diatom that is found in streams with high salinity and high electrolyte concentration. To date, no specific type of freshwater has been identified. In this study, a new species of freshwater diatom, Entomoneis Parikhani, is described based on detailed morphological observations using a scanning electron microscope. The studies were conducted in the Ares River in northwest Iran. An unknown taxon belonging to the genus Entomoneis was found in Oltan village of Parsabad city. The Aras River contains freshwater. A special feature of Entomoneis Parikhani is its triple valve. The genus Entomoneis comprises of diatoms with sigmoidal raphe canals and girdle bands. This taxon is similar to Entomoneis annagodhei and Entomoneis tenera, as shown by LM and SEM observations, and there are sufficient morphological differences to separate Entomoneis Parikhani sp. Entomoneis Parikhani sp found in fresh water and similar species found only in salt water. This new species had very small cells, delicate frustules without valve lines, and wide lanceolate valves. In this study, the wide distribution of this taxon in the Aras River and its tributaries has been discussed in terms of water quality variables.