Oxynoemacheilus sarali (Teleostei: Nemacheilidae): a new species of loach from Merziman Creek, Euphrates River Basin, Türkiye, described using a morpho-molecular approach

Abstract

The genus Oxynoemacheilus is distributed across the Eastern Mediterranean, the southern Caucasus, Anatolia, Mesopotamia, and Central Iran. To date, 67 species belonging to the genus have been described. Among these, 49 species are found in T & uuml;rkiye, of which 38 endemic for the country. The present study re-evaluates the Merziman Creek population (Euphrates drainage), previously identified as O. tigris, using an integrative approach combining mitochondrial (COI), nuclear (S7 intron1) markers, and morphometric data. Results support its description as a new species, Oxynoemacheilus sarali sp. nov. Phylogenetic analyses reveal that O. sarali forms a distinct, well-supported clade supported by high genetic divergence compared to all other congeners. Additionally, O. sarali morphologically differentiate from other species by combination of characters follows as; an incomplete lateral line, unique mouth shape, 9-13 grey narrow bars on the flank, a long dorsal adipose crest on the caudal peduncle (19-28% SL), a deep caudal pedincule and absence of a suborbital groove in males. These findings confirm O. sarali as a distinct species and highlight the need for ongoing assessment of loach diversity in Anatolia. This study also provides the first nuclear (S7) and concatenated (COI + S7) phylogenies for Oxynoemacheilus, enriching understanding of regional freshwater fish biogeography.