A new loach of the genus Oxynoemacheilus from the Tigris River drainage and its phylogenetic relationships among the nemacheilid fishes (Teleostei: Nemacheilidae) in the Middle East based on mtDNA COI sequences

Oxynoemacheilus parvinae, new species, from the tributaries of the Iranian Sirvan River drainage, belongs to a group of Oxynoemacheilus having a suborbital groove in males and elongated body. It is distinguished from the other species of this group in the Tigris River drainage by a combination of the following characters: 8½-9½ branched dorsal-fin rays, large to medium dark-brown spots especially on the post-dorsal part, emarginated caudal fin, angular shape of bony capsule of swim bladder with developed posterior process, longer head and shallower body. It is also diagnosed from its nearest species (O. bergianus and O. longipinnis) by two fixed, diagnostic nucleotide substitutions in the mtDNA COI barcode region, and a K2P nearest-neighbour distance of 1.4% to O. longipinnis. Maximum Likelihood and Bayesian phylogeny reconstructed based on COI barcode region place the sequenced nemacheilid fish into a monophyletic clade which show between 1.4 % (O. parvinae vs. O. longipinnis) and 16.3 % (O. longipinnis vs. O. merga) K2P sequence divergence.