Cephalic osteology of Safidrud stone loach Oxynoemacheilus bergianus

The hillstream loach subfamily Nemacheilinae are difficult to identify because of difficulties in extracting their morphological traits and they consider to be a complex group in terms of taxonomy. Therefore، their classification established based on osteological ground. Also، study of head osteology can help to better understanding of biological characteristics such as feeding and respiration. Hence، this study was aimed to provide the characterization of the cephalic osteology of Safidrud stone loach Oxynoemacheilus bergianus from Sefidrood River. For this study sixteen specimens of Safidrud stone loach were collected using electrofishing. Specimens were fixed into four percent buffered formalin after anaesthetizing and then cleared and stained with alizarin red S and alcian blue for osteological examinations. The Safidrud stone loach shows differences in the shape of neurocranium، bony elements forming suspensorial facets، connecting position of lateral ethmoid، possessing urohyal extra and shape of pectoral fin radial in compare to other member of the genus Oxynoemacheilus، considering as special osteological characters of this species. Regarding the weakness of morphometric، meristic and color pattern traits for taxonomic study of the member of genus Oxynoemacheilus، the finding of this research can use for future taxonomic studies of this taxon.