Taxonomy & naming
Oxynoemacheilus nasreddini was formally described in 2021 by Yusuf Yoğurtçuoğlu, Cüneyt Kaya and Jörg Freyhof in Zootaxa 4974(1), part of the ongoing revision of Anatolia's stone loaches — a group that spent decades lumped under broad, catch-all names like Noemacheilus or Nemacheilus before molecular and morphological work split it into the modern genera Oxynoemacheilus, Schistura, Paracobitis, Barbatula and others. The species belongs to family Nemacheilidae, the stone or brook loaches, the largest family in the loach superfamily Cobitoidea.
Molecular data placed it as a close relative of Oxynoemacheilus mediterraneus, separated by roughly 1.2% mitochondrial COI divergence — a small but, combined with consistent morphological differences, diagnostic distance in this genus's fine-grained taxonomy. Karyotype work found 30 biarmed and 20 monoarmed chromosomes. The genus name Oxynoemacheilus is itself a refinement of the older Noemacheilus, and as with many of its congeners this species has never carried another combination — it was named directly into its current genus, so there is no synonym trail to untangle here.
Morphology
The original description characterizes Oxynoemacheilus nasreddini by a slender body marked with irregularly shaped blotches along the flank, and a caudal fin crossed by two to four dark-brown bands, the fin itself emarginate (shallowly notched) rather than rounded or deeply forked. This pattern — irregular flank blotching plus a banded tail — is a useful field mark distinguishing it from closely related basin endemics.
As in other Oxynoemacheilus, expect the typical stone-loach build: an elongated, subcylindrical body, a flattened belly suited to gripping the substrate in current, and small paired fins used to brace against the flow. Size has not been recorded in the available literature; congeners in the genus typically run in the range of about 1.5–3 in standard length, and that is offered here only as a genus-level guide, not a measured figure for this species specifically.
Habitat
This species is endemic to a set of closed (endorheic) drainage basins in Central Anatolia, Turkey — the Akşehir, Eber, Eğirdir and Ilgın basins — a region of lakes and spring-fed streams sitting on limestone geology. Genus-typical habitat for Oxynoemacheilus is clear, cool-to-cold, fast-flowing, well-oxygenated water over gravel and stone, often fed by springs, and the species almost certainly occupies streams of this kind within its home basins, though exact temperature and pH have not been documented for it specifically.
Because each of these Anatolian basins is hydrologically closed, a species confined to one or a few of them is entirely dependent on that basin's water levels and quality — there is no possibility of natural recolonization from outside if a local population is lost. Nothing here suggests a species outside temperate Eurasia; this is unambiguously a cool-water Anatolian stream fish, not a warm tropical one.
Feeding
No feeding study has been published for Oxynoemacheilus nasreddini. By family and genus habit it is presumed to be a benthic micro-predator, picking small aquatic invertebrates — insect larvae, worms and tiny crustaceans — off gravel and stones in flowing water, the standard diet pattern documented across Nemacheilidae generally.
In the complete absence of aquarium records, nothing can be said about feeding response in captivity; this is noted here as data-sparse rather than guessed at.
Mating
No courtship, spawning trigger, or sexual dimorphism has been documented for this species in the literature consulted. Stone loaches in this genus are not known to show strong external sexual dimorphism outside of general body proportion differences seen across the family, and nothing specific can be reported for O. nasreddini.
Breeding
Breeding biology has not been studied or recorded for Oxynoemacheilus nasreddini specifically. Based on the pattern seen across Nemacheilidae, the species is presumed to be an egg-scatterer, releasing eggs over gravel and among stones in flowing water with no parental care afterward — but this is an inference from the family, not a direct observation of this species. There is no record of it being bred, or even kept, in captivity; as a fish described only in 2021 from remote Anatolian drainages, it has essentially no aquarium history. The honest summary is that breeding data for this species is sparse to nonexistent.
In the aquarium
Oxynoemacheilus nasreddini is not established in the aquarium hobby. It does not appear to have entered the ornamental trade, has no dedicated care literature, and — as a species-level endemic of a handful of closed Central Anatolian basins described only in 2021 — is unlikely to be available to hobbyists in the foreseeable future. Anyone encountering material labelled with this name should treat identification with caution given how easily Anatolian Oxynoemacheilus species are confused with one another.
Were it ever kept, general Oxynoemacheilus husbandry would apply: cool, clean, fast-moving, well-oxygenated water over a gravel or stone substrate, since these are cool-water stream fish rather than warm still-water species. As with other nemacheilids, a scaleless or near-scaleless skin would be expected to make it sensitive to copper-based medications and full-strength treatments, though this has not been tested for this species.
Conservation
Oxynoemacheilus nasreddini has not yet been assessed on the IUCN Red List and is recorded here as Not Evaluated rather than assigned a guessed status. As a narrow-range endemic restricted to a small number of closed Central Anatolian drainage basins, it shares the structural vulnerability common to many recently described Anatolian stream fishes: any single population is dependent on that basin's water levels, agricultural and municipal water extraction, and water quality, with no possibility of natural rescue from outside populations given the closed hydrology.
No population trend, threat assessment or trade pressure has been documented for this species. Given how recently it was described (2021) and how restricted its known range is, a formal IUCN assessment specific to this species would be valuable but does not yet exist.