Taxonomy & naming
Louis Lortet described this species in 1883 as Nemachilus leontinae, based on material from Lake Tiberias (the Sea of Galilee) in what is now Israel; the lectotype, a fish of 2.5 in standard length, is held at the Musée des Confluences in Lyon (MHNL 3665). For much of the twentieth century the name languished as a presumed synonym of Orthrias panthera, another Levantine stone loach, and the population was not treated as a distinct, valid species in most regional accounts.
Freyhof & Kottelat's 2012 revision of the Middle Eastern nemacheilids revalidated Nemachilus leontinae as a good species and placed it in Oxynoemacheilus, the genus now recognized by the Catalog of Fishes (Eschmeyer, CAS) — the standing authority for valid names — for most of the region's stone loaches formerly lumped in the old catch-all genera Nemacheilus and Noemacheilus. The species therefore stands today as Oxynoemacheilus leontinae (Lortet, 1883), family Nemacheilidae, the largest and most species-rich family of true loaches.
Morphology
Oxynoemacheilus leontinae is a small, slender, cylindrical loach typical of its genus: an elongated body, a rounded snout, and barbels around the mouth used to feel out food on the substrate. As in other nemacheilids it lacks the erectile suborbital spine that defines the botiid loaches (clown, yoyo, zebra loaches and kin) — that structure is absent from this family entirely, one of the clearest anatomical lines separating stone-and-brook loaches from the spined-loach lineages.
The skin is essentially scaleless or bears only minute, deeply embedded scales, a trait shared across the true loaches and one with direct consequences for how the species should be handled and medicated. Detailed morphometric data beyond the original description and its lectotype measurement (2.5 in SL) are sparse in the available literature, so precise adult proportions and colour pattern are not well documented here; this is a genuinely under-studied, single-region endemic rather than a widely characterized aquarium species.
Habitat
The species is native to the Jordan River and Litani River systems, spanning Israel, Lebanon and Syria, with its type locality at Lake Tiberias (the Sea of Galilee) itself. The Jordan basin runs from spring-fed, fast, cool tributary streams down into slower, warmer sections near the lake, and the fact that the type specimen came from the lake margin suggests this species tolerates a range of conditions from flowing tributary water to calmer main-basin habitat, though like most of its relatives it is most at home in clear, running freshwater over rocky or gravel substrate.
This is a coolish to moderate freshwater habitat, not a warm, still blackwater system — a point worth stressing because it is easy to default to "tropical loach" assumptions that do not fit a Levantine, largely stream-and-lake-margin fish.
Feeding
Like other Nemacheilidae, Oxynoemacheilus leontinae is a benthic micro-predator, working the streambed for small aquatic invertebrates — insect larvae (including dipterans), small crustaceans, and other invertebrate prey — supplemented with some organic detritus picked up incidentally while foraging. Its barbel-lined mouth and constant nose-down grubbing over gravel are the visible signs of this feeding style.
No aquarium-specific feeding data are documented for this exact species, but based on the family's well-established habits it would be expected to take small sinking live and frozen foods (bloodworm, brine shrimp, small worms) readily, with limited interest in flake or floating foods that never reach the bottom.
Mating
Specific courtship and pairing behaviour has not been documented for this species. Across Nemacheilidae generally, spawning is a seasonal event tied to spring and summer conditions (roughly March to July in comparable species), triggered by rising water temperatures and increased flow rather than by any elaborate pair-bonding display. There is no reported sexual dimorphism data for O. leontinae in the sources available, and none is asserted here.
Breeding
As in other stone and brook loaches, breeding in this species is expected to follow the family pattern: an egg-scatterer, releasing eggs among stones and gravel in fast-flowing shallow water at a temperature in the general range of 61–77 °F typical for the family, with no parental care of eggs or fry afterward. There is no record of this species being deliberately bred in captivity, and data on its reproduction even in the wild are limited to inference from better-studied relatives — a fair statement given how narrow and specialized the published literature on this particular species is.
Honest framing matters here: Oxynoemacheilus leontinae is not a fish with a documented aquarium breeding history. Anyone encountering it in the hobby should expect a wild-collected or research specimen rather than a captive-bred one.
In the aquarium
Oxynoemacheilus leontinae is essentially unknown in the ornamental trade and is not a species with an established aquarium track record; almost everything a keeper would need is inferred from its family and native habitat rather than from hobbyist experience. Housing should reflect a small, active, scaleless bottom-dweller from moderate-flow, well-oxygenated freshwater: a fine sand or smooth gravel substrate it can forage over without abrasion, decent current and oxygenation, and rockwork or gravel it can nose through for invertebrate prey.
As with all near-scaleless true loaches, medication sensitivity is a serious practical concern — copper-based treatments and full-strength doses of many standard medications can be poorly tolerated, so any treatment should start conservative and be watched closely. Given how sparse the documentation is for this exact species, a cautious, research-minded keeper rather than a casual buyer is the appropriate audience, and any specimen in the trade should be treated as wild-collected.
Conservation
The IUCN Red List assesses Oxynoemacheilus leontinae as Least Concern, indicating a population considered stable within its native Jordan and Litani river range. That range, however, spans a geopolitically fragmented and heavily water-stressed part of the Middle East — the Jordan River basin is one of the most intensively dammed, diverted and abstracted river systems in the world, shared and contested across Israel, Lebanon, Syria and Jordan — so a favourable Red List category should not be read as freedom from pressure; it reflects the assessment available rather than a guarantee of long-term security.
There is no evidence in available sources of a trade-driven threat to this species; it is not a commercially collected ornamental fish. Any conservation concern would run instead through habitat-scale pressures on the Jordan and Litani systems themselves — water extraction, damming and pollution — rather than aquarium demand.