Oxynoemacheilus nasreddini

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 524-525

Oxynoemacheilus nasreddini

Common name. Eber loach.

Diagnosis. Distinguished from other species of Oxynoemacheilus in Central Anatolia and rivers flowing to Bay of Antalya by: ○ a prominent inner axial stripe along midlateral flank / ○ body usually with a series of vertically elongated blotches / ○ tip of pectoral usually reaching to or slightly beyond pelvic origin in male / ○ body depth decreasing between dorsal and caudal base / ○ belly with few, small, embedded scales / ○ caudal–peduncle depth 1.5–2.1 times in its length / ○ caudal emarginate, shortest middle caudal ray 76–91 % of longest ray of upper caudal lobe / ○ prepelvic length 48–55 % SL / ○ usually a series of short bars on caudal

peduncle / ○ 2–4 dark-brown bands on caudal / ○ suborbital groove present in male. Size up to 78 mm SL.

Distribution. Türkiye: Lakes Akşehir, Eber, Eğirdir and Ilgın basins.

Habitat. Slow-flowing streams with gravel or mud bottom.

Biology. No data.

Conservation status. VU; appears to be declining within its small range and has lost several habitats in recent years due to desiccation of streams and massive pollution.

Remarks. Populations from Lake Eğirdir basin share the mtDNA with O. mediterraneus , indicating a past introgressive hybridisation.

Further reading. Yoğurtçuoğlu et al. 2021a (description).

The use and misuse of DNA barcoding for taxonomy.

“…a classification founded on any single character, however important that may be, has always failed.”

—Charles Darwin (1859)

The advent of molecular techniques has provided new tools for species identification, revolutionising the taxonomic methodology within less than two decades. One of the most widely applied methods compares nucleotide sequence similarity among organisms and attributes it to species differences. For this, sequencing a short fragment of the mitochondrial gene, i.e., cytochrome c oxidase subunit 1 ( COI or DNA barcode), was hailed as a “magical

tool” or “the taxonomy of the twenty-first century.” Since its inception, DNA barcoding has become a widely accepted and standardised protocol for species identification worldwide. However, as with any single-character approach, it must be applied cautiously. Some believe that the barcoding gene was placed in all organisms by a higher entity to allow scientists to recognise species. This viewpoint is not as uncommon as one might suspect.

The arguments against the approach have been consistently presented. The primary criticism is based on the opposition to the assertion of the proponents of the barcoding approach, who have declared that if two organisms show a “considerable” nucleotide difference, they would be considered different species, or vice versa. The assertion is open to serious debate for three reasons. Firstly, the reduction of the complex evolutionary history of organisms to a single character: phylogenetic distance, is employed as a species concept. Secondly, no reasonable distance threshold is provided by which species can be demarcated. Thirdly, the confusion between diagnosis (assigning a fish to an already known species) and definition (deciding if a group of individuals is a species) is evident. In the real world, species are evolving entities, and phylogenetic (or COI) distance can be understood as a measure of proximity to the number of generations (time) that have passed since the last gene flow between populations.

The species concept that DNA barcoding represents ignores the existence of old and young species, where phylogenetic distance is of no consequence. This is because, while speciation does not always require a long period that leads to high phylogenetic distances, genetic divergence does not necessarily lead to speciation. Furthermore, there are several theoretical pitfalls in applying the barcoding approach, in which untrained practitioners (both taxonomists and molecular biologists) have always been prone to being trapped. For instance, at least in the case of fishes, mitochondrial capture through introgressive hybridisation is much more common than previously thought. Consequently, the sole use of COI DNA sequences to identify an individual with mitochondrial DNA introgressed by another species will result in an erroneous identification.

Oxynoemacheilus panthera ; Litani drainage, Lebanon; 60 mm SL.