Taxonomy & naming
The species was described in 1948 by the Swedish ichthyologist Hjalmar Rendahl in his monograph on the freshwater fishes of Burma, "Die Süßwasserfische Birmas," not as a full species in its own right but as a subspecies of a relative, Nemacheilus rubidipinnis mandalayensis — a trinomial that ties the population directly to Mandalay, in the heart of the Irrawaddy drainage where it was first collected. Rendahl placed it in the family he treated broadly as Cobitidae, the classification in use at the time.
Maurice Kottelat elevated the Mandalay population to full species status in 2012, as Acanthocobitis mandalayensis, recognizing it as distinct from Acanthocobitis rubidipinnis. The name Acanthocobitis mandalayensis has therefore also been used for this fish; a subsequent revision of the zipper loaches by Singer & Page, published in Copeia in 2015 and describing five new species in the process, moved the whole rubidipinnis group — mandalayensis included — into a further-split genus, Paracanthocobitis, and the Catalog of Fishes now lists Acanthocobitis mandalayensis as a synonym of the currently valid Paracanthocobitis mandalayensis. This kind of repeated reshuffling is typical of the family: the old catch-all genera Nemacheilus and Noemacheilus have been split repeatedly over the last two decades into narrower genera such as Schistura, Triplophysa, Barbatula and Acanthocobitis/Paracanthocobitis, and older literature or hobby material may still list this fish under any of the three names — Nemacheilus, Acanthocobitis or Paracanthocobitis.
The species is placed in the family Nemacheilidae — the largest of the loach families and the one that holds most of the small, scaleless, fast-water "brook" loaches of Eurasia.
Morphology
This is a small, slender, cylindrical loach, reported to reach about 3.5 in in standard length. It shows the classic nemacheilid toolkit: a complete lateral line running the length of the body, a lower lip formed as a papillated pad with a median notch, and an axillary pelvic lobe. The dorsal fin carries roughly ten and a half branched rays, and the caudal fin is marked with four to eight dark bands — a useful field character within the genus.
A dark ocellus (eye-spot) sits near the base of the tail, a common feature in stone loaches thought to help deflect predator strikes away from the head. Males can be told from females by a suborbital groove, a trait shared across many Paracanthocobitis and Acanthocobitis species tied to the small erectile spine seated below the eye — the defensive spine common to nemacheilid and botiid loaches alike, though smaller and less conspicuous here than in the larger botiids. Like other members of the family it is essentially scaleless to the touch, with tiny embedded scales that leave the skin exposed and sensitive.
Habitat
Paracanthocobitis mandalayensis is native to river systems in Myanmar and northwestern Thailand: it is recorded from the Irrawaddy drainage in northeastern Myanmar, the Sittang basin in the south of the country, and the Wang and Ping rivers of the Chao Phraya basin in northwest Thailand. These are the flowing, well-oxygenated freshwater channels typical of nemacheilid habitat across mainland Southeast Asia — clear to moderately turbid streams and rivers with gravel, sand and rock substrates.
As a demersal (bottom-dwelling) freshwater species, it spends its life close to the substrate in current, in the company of the many other small loaches, barbs and hillstream fishes that share these Irrawaddy- and Chao Phraya-basin waters. Specific data on water chemistry and seasonal conditions at its collection sites is not available; it should be treated as a fast, clear, well-oxygenated stream fish rather than a still-water species.
Feeding
Detailed dietary data for this species has not been published, but its build and habitat point clearly to the same strategy seen across the stone-loach genus: a benthic micro-predator picking small invertebrates, insect larvae and other tiny prey from gravel and sediment in flowing water, in the manner documented for its close relative Acanthocobitis botia.
In the aquarium, related Paracanthocobitis and Acanthocobitis species take small live and frozen foods readily — Daphnia, Artemia and bloodworm — alongside sinking dried foods, and this is a reasonable template to follow here. Food should reach the bottom, since this is not a fish that competes well for food in the water column.
Mating
No published account of courtship or spawning behaviour in Paracanthocobitis mandalayensis specifically is available. External sexual dimorphism in the genus is limited to the suborbital groove noted in males of related species, which is not a reliable field character for casual sexing; body girth in gravid females is the more practical cue, as it is across most small nemacheilids.
Across the wider family, spawning is understood to happen in the water column over gravel in flowing water, without courtship displays or pair bonds of the kind seen in cichlids — a simple broadcast-spawning strategy rather than anything more elaborate. There is no reason to expect this species differs from that pattern, but it has not been documented directly.
Breeding
Nemacheilidae as a family are egg-scatterers: males and females spawn together in the water column, and the fertilized eggs drift with the current into gravel crevices, where they are left with no parental care. Fry that hatch graze on microscopic life in the gravel for their first weeks. This matches the general pattern for stone and brook loaches worldwide, and it is the best available guide to how Paracanthocobitis mandalayensis is likely to reproduce.
There is no record of this species being bred in the home aquarium, and data on it is sparse generally. As with the great majority of small nemacheilid loaches, it should be assumed effectively unbred in captivity; any specimens in the trade are almost certainly wild-collected rather than farm- or hobbyist-produced.
In the aquarium
Hard data specific to this species is limited, so care should draw on its close relatives and its known habitat. Related Paracanthocobitis and Acanthocobitis species are kept at 70–79 °F over sand or fine gravel, with rockwork and caves for cover and reasonably strong water movement and oxygenation reflecting their fast-flowing native streams — this is not a fish for a warm, still, heavily planted tank. A sinking diet of small live, frozen and prepared foods suits its bottom-feeding, invertebrate-hunting habits.
As with virtually all nemacheilid and botiid loaches, the near-scaleless skin makes this species sensitive to copper-based medications and full-strength treatments generally; half-doses and gentle products are the safer route if disease treatment is ever needed. Given how little is documented about this particular species' social behaviour, keeping it in a small group rather than alone is the cautious choice, in keeping with general stone-loach husbandry. Adult size stays under 3.5 in, so a modestly sized species or community tank is adequate, provided flow and oxygenation are kept high.
Conservation
Paracanthocobitis mandalayensis has not been evaluated by the IUCN Red List, so it carries no conservation category — recorded here as Not Evaluated rather than assumed safe. Given how many small Southeast Asian stream loaches remain data-deficient or unassessed, this is a common status for the group rather than a sign of unusual rarity or safety.
Its range spans river systems in Myanmar and northwestern Thailand that face the general pressures common to the region's freshwater habitats — damming, agricultural runoff, sedimentation and development — but no species-specific assessment of population trend or trade impact is available. The species does not appear to be a significant part of the aquarium trade, and there is no evidence of any dedicated collection pressure on it.