Taxonomy & naming
Oreonectes macrolepis was described in 2009 by Huang, Du, Chen & Yang in the journal Zoological Research, based on specimens from an underground river at Dacai Town, Huanjiang County, in the Guangxi Zhuang Autonomous Region of southern China. It was placed in Oreonectes, a genus of stone loaches (family Nemacheilidae) built largely around cave-adapted and cave-associated species from the karst uplands of southern China.
In 2016, Zhang & Zhao revised the troglobitic members of this group and moved the species into a newly recognised genus, Troglonectes — a name that transparently means "cave swimmer" — reflecting the fully hypogean, obligate-cave lifestyle shared by this cluster of species. FishBase and a number of other reference sources still list the fish under its original combination, Oreonectes macrolepis, and that is the name used here; a keeper or researcher encountering it as Troglonectes macrolepis in more recent literature is looking at the same animal under its current valid combination.
Morphology
This is a small loach, reaching only about 3 in in standard length at maximum recorded size — modest even by the standards of the stone-loach family. The species epithet macrolepis, "large-scaled," refers to the comparatively large scales that distinguish it from close relatives, one of the characters used to separate it from other Oreonectes/Troglonectes species in the original description.
As a nemacheilid it shares the family's slender, cylindrical, bottom-hugging body plan and lacks the erectile suborbital spine found in the unrelated botiid loaches. Living cave loaches in this genus typically show the classic troglomorphic suite — reduced eyes and reduced pigmentation compared to surface-dwelling relatives — though the original description and available sources do not give a detailed account of pigmentation or eye reduction specific to this species, so those details are best treated as inferred from its close, better-studied relatives rather than confirmed for macrolepis itself. Like other true loaches it is essentially scaleless in effective terms, with tiny, deeply embedded scales, leaving it sensitive to handling and medication.
Habitat
Oreonectes macrolepis is known only from its type locality: an underground river at Dacai Town, Huanjiang County, Guangxi, China, part of the Pearl River (Xijiang tributary) drainage. It is troglobitic — an obligate cave-dweller restricted to subterranean, karst-influenced groundwater, not a surface stream species. The habitat is total darkness, limestone substrate, and the slow-to-moderate flow typical of underground river passages carved through karst.
Water chemistry and temperature at the type locality are not documented in the accessible literature. Karst groundwater in this part of southern China is generally cool and likely neutral to mildly alkaline given the limestone geology, but that is a reasonable inference rather than a measured fact, and no aquarium-relevant water parameters can honestly be given for this species.
Feeding
No diet study has been published for this species. By analogy with other small nemacheilid stone loaches — micro-predators that forage over stream and cave substrates for small invertebrates and insect larvae — it is reasonable to expect Oreonectes macrolepis feeds similarly on whatever small invertebrate life is available on the substrate of its cave system. Cave ecosystems generally have far less food input than surface streams, so its foraging ecology and metabolic demands in perpetual darkness are likely quite different from surface-dwelling relatives, but this remains unstudied and should be treated as data-sparse rather than assumed.
Mating
Nothing has been published on courtship or spawning behaviour in this species. The one reproductive detail on record is anatomical rather than behavioural: males possess enlarged genital papillae posterior to the anus, a feature noted in troglobitic relatives in this genus group and thought to relate to a specialised reproductive strategy in cave-dwelling loaches, though its precise function here is not established. Beyond that, courtship, timing, and any environmental spawning triggers are unrecorded.
Breeding
As with the great majority of stone and brook loaches, Oreonectes macrolepis is presumed to be an egg-scatterer with no parental care, the standard reproductive mode across Nemacheilidae. No spawning of this species — in the wild or in captivity — has been documented, and given its restriction to a single subterranean locality and complete absence from the aquarium trade, that is unsurprising. This is a species for which the honest statement is simply that its breeding biology is unknown.
In the aquarium
Oreonectes macrolepis is not a fish anyone is likely to encounter in the hobby. There is no record of it being kept, imported, or bred in aquaria, and as a true troglobite adapted to permanent darkness, stable cave-water chemistry, and an ecology built around a food-poor subterranean environment, it would be an extraordinarily difficult species to maintain even if specimens became available. Any general nemacheilid care principles — cool, clean, well-oxygenated water and a soft, sensitive, near-scaleless body that reacts badly to copper and to full-strength medication — would presumably apply, but none of this has actually been tested on the species itself. This is a fish that belongs in the scientific record rather than the aquarium trade.
Conservation
Oreonectes macrolepis has not been evaluated by the IUCN Red List and carries no formal conservation status. It is known only from a single underground river system in Huanjiang County, Guangxi — an extremely narrow range that, by its nature, would make the species highly vulnerable to any disturbance of that specific karst groundwater system, from pollution to changes in water table or land use above the cave. Southern China's karst cave faunas as a group face exactly these kinds of localised pressures. In the absence of a formal assessment, the responsible statement is that this is a narrow-range subterranean endemic with an unknown but presumably precarious conservation outlook, not a species with any recorded trade pressure — it is not known to be collected for the aquarium hobby.