Taxonomy & naming
Yunnanilus macrolepis was described by Li, Tao and Mao in 2000, in a paper covering two new species of Yunnanilus from eastern Yunnan, China, published in Acta Zootaxonomica Sinica (volume 25, issue 3, pages 349–353) under the title "Two new species of Yunnanilus from eastern Yunnan, China (Cypriniformes: Cobitidae)." At the time the family Nemacheilidae was still commonly treated as a subfamily within Cobitidae; modern taxonomy, following the Catalog of Fishes, recognizes Nemacheilidae as its own family, and Yunnanilus macrolepis sits within it as originally combined — no genus change has been applied to this species.
The genus Yunnanilus is named for Yunnan province, China, where the great majority of its species are endemic, and is one of many small stone-loach genera carved out of the old, overly broad Nemacheilus/Noemacheilus complex as regional faunas were revised through the twentieth and twenty-first centuries. The species epithet macrolepis reflects a distinguishing scale character noted in the original description, separating it from congeners collected in the same eastern Yunnan survey.
Morphology
As a member of Nemacheilidae, Yunnanilus macrolepis has the elongated, cylindrical body typical of stone and brook loaches, with FishBase recording 10–11 dorsal soft rays and 7 anal soft rays for the species. Like other nemacheilids it is a small, bottom-hugging fish built for holding station in current rather than for open swimming, and like its relatives it likely carries a small erectile suborbital spine and the near-scaleless, thin skin typical of the family, though no published description specifically confirms these details for this species.
No maximum length, weight, or detailed body-proportion data have been published for Yunnanilus macrolepis. Species in this genus are uniformly small — most Yunnanilus top out at only a few centimetres — but without a documented figure for this species specifically, any number would be a guess. The honest position is that its size is currently undocumented in the literature available to this profile.
Habitat
Yunnanilus macrolepis is a demersal freshwater species endemic to China, with its type locality in Luoping County, in eastern Yunnan province, within the Pearl River (Zhu Jiang) drainage basin in southeastern China. Like the great majority of Yunnanilus species, it is presumed to live in small, clear, flowing streams — the typical habitat of the genus across the Yunnan plateau — though no detailed habitat survey specific to this species has been published.
No water chemistry, temperature, or flow data have been recorded for the type locality or any other site where the species has been collected. Given its placement within Yunnanilus and the broader Nemacheilidae, a cool-to-moderate, well-oxygenated, flowing stream environment is the reasonable inference, but this profile does not assign specific temperature or pH figures that have not actually been measured and published for the species.
Feeding
No dietary study has been published for Yunnanilus macrolepis. Stone and brook loaches as a group are bottom-foraging micro-predators, working the substrate of fast, clear streams for small invertebrates such as insect larvae and tiny crustaceans, and this is the general pattern expected of any undocumented Nemacheilidae species including this one.
In the complete absence of species-specific feeding data, keepers considering any close relative in the genus should plan around that general stream-forager profile — small sinking live, frozen, or prepared foods offered at the bottom — rather than any documented specifics for Yunnanilus macrolepis itself, which simply do not yet exist in the literature.
Mating
Nothing has been published on courtship, spawning behaviour, or sexual dimorphism in Yunnanilus macrolepis. No original description details or subsequent aquarium reports address how the sexes differ or how the species pairs and spawns.
For context, related Yunnanilus species that have been kept and observed in aquaria — such as Y. brevis and Y. cruciatus — are reported as gregarious free spawners with no elaborate courtship ritual, scattering eggs rather than forming pairs or nests. Whether that pattern extends to Y. macrolepis is unconfirmed; it is offered here only as the general expectation for the genus, not as a documented fact about this species.
Breeding
Yunnanilus macrolepis has, as far as the available literature shows, never been bred in the aquarium, and no breeding observations exist even from the wild beyond its basic classification as an egg-laying cypriniform. Based on the general pattern for stone and brook loaches — and on what has been reported for other Yunnanilus species kept in aquaria — the expected mode is an egg-scatterer that releases eggs over gravel or among stones in flowing water, with no parental care afterward.
That expectation should be read as an inference from the genus and family, not a confirmed fact about this species. Data on this species is sparse to the point of being effectively absent, and any keeper hoping to breed it should treat the endeavour as genuinely experimental rather than something with an established protocol to follow.
In the aquarium
Yunnanilus macrolepis does not appear to be established in the aquarium trade, and no dedicated care profile exists on the major hobbyist reference sites. It is not listed with English trade names, and searches of loach-specialist resources return no species-specific husbandry notes — only general information about the genus as a whole.
A keeper who did encounter this species should default to general Nemacheilidae practice until better information exists: cool-to-moderate, clean, well-oxygenated, flowing water; a fine sand or gravel substrate the fish can forage over; and caution with medications, since scaleless and near-scaleless loaches as a group tend to be sensitive to copper and full-strength treatments. Given how little is documented, sourcing would almost certainly mean wild-collected fish from its narrow Yunnan range rather than any commercially farmed stock, which is itself a conservation consideration worth weighing before acquiring it.
Conservation
Yunnanilus macrolepis has not been evaluated by the IUCN Red List, so it carries no formal conservation category; this profile records that honestly as Not Evaluated rather than assigning a status that has not been assessed. Its known range is narrow — apparently restricted to streams in the Pearl River basin of eastern Yunnan, centred on the Luoping County type locality — which is the kind of small-range endemism that, across the genus Yunnanilus generally, has previously translated into real conservation concern once species are formally reviewed.
No population trend, threat assessment, or protection status has been published for this species specifically. Stream-endemic Nemacheilidae in southern China face pressures typical of the region — damming, water diversion, pollution, and habitat alteration — but without a formal assessment for Yunnanilus macrolepis, this profile cannot responsibly go beyond noting that it is a small-range, data-poor species in a region under general freshwater habitat pressure.