Taxonomy & naming
Paracanthocobitis canicula was described by Singer & Page in 2015 in Copeia 103(2): 378–401, as part of a revision of stone loaches from the Mekong basin. It belongs to Nemacheilidae, the largest family of loaches, a group of small, mostly benthic "stone" or "brook" loaches spread across Eurasia. The genus Paracanthocobitis itself is relatively young in the literature, carved in recent decades out of the old broad wastebasket genera Nemacheilus and Noemacheilus as those groups were split apart using better anatomical and molecular characters — a pattern repeated across Cobitoidea, where names such as Schistura, Triplophysa and Barbatula now carry species once lumped together.
The species epithet canicula is Latin for "little dog." The original description explains this as a reference to the jagged, canine-tooth-like shape of the dark saddles that cross the fish's back — a distinctive marking used, along with its complete lateral line, an axillary pelvic lobe, and a male suborbital groove, to separate it from its closest relatives in the Mekong drainage.
Morphology
This is a small, slender nemacheilid loach, reaching only around 2.5 in in standard length. As in other stone loaches, the body is elongate and subcylindrical, built for holding position on the bottom in current rather than for open-water swimming. The original description notes a complete lateral line running the length of the body, an axillary pelvic lobe, and — in males — a groove beneath the eye associated with the small, erectile suborbital spine typical of the loach superfamily Cobitoidea.
Patterning is the fish's most diagnostic feature: jagged, tooth-shaped dark saddles run along the back, large squarish blotches sit below the lateral line, a round black spot marks the base of the tail, and the caudal fin carries five to seven dark bands. The pelvic fins have eight rays. As with most nemacheilids, the skin carries only fine, deeply embedded scales, leaving it functionally near-scaleless — a trait that matters for how the fish should be medicated in captivity.
Habitat
Paracanthocobitis canicula is known from the lower Mekong basin in Cambodia. Its type locality is O Kap, at a ford on Highway 197 about 4 mi south of the Sasane River, itself a tributary of the Mekong, near 13.87°N, 107.30°E — a small, flowing tributary stream rather than the main river channel. Like most nemacheilids it is a demersal, freshwater fish, holding to the bottom of clear, running water over stone, gravel and sand.
Beyond the type locality, published habitat detail for this species is limited; it is one of many small Mekong-basin stream endemics that are known from few collection records. As a tropical Southeast Asian stream loach it inhabits warmer water than temperate stone loaches such as the European Barbatula or high-altitude Triplophysa, but it still depends on the well-oxygenated, flowing conditions typical of the family.
Feeding
No dedicated dietary study has been published for Paracanthocobitis canicula, and the original description does not detail its natural diet. Based on the ecology of Paracanthocobitis and other Mekong-basin stone loaches, it is reasonable to expect it forages over the streambed for small invertebrates — insect larvae, worms and tiny crustaceans — in the manner typical of the genus, but this should be treated as an inference from its relatives rather than a confirmed fact for this species specifically.
In the aquarium, stone loaches of this type generally do well on small sinking foods: fine sinking pellets or wafers alongside frozen bloodworm, daphnia or brine shrimp, offered where a bottom-dwelling micro-predator can reach them ahead of faster fish. Flake that sits on the surface is of little use to a fish that feeds on the bottom.
Mating
The original description notes a male suborbital groove, which implies some external sexual dimorphism is present in this species, but no broader account of courtship or spawning behaviour has been published. Nothing is documented about seasonal timing, pairing, or spawning triggers in the wild for Paracanthocobitis canicula specifically.
Across Nemacheilidae generally, stone and brook loaches are egg-scatterers that spawn over gravel or among stones in flowing water with no parental care, often cued by seasonal rises in flow. It is reasonable to assume P. canicula follows this general family pattern, but this has not been confirmed for the species itself, and the point should be read as an inference rather than an observed fact.
Breeding
There is no published breeding record for Paracanthocobitis canicula, in the aquarium or in the wild. Consistent with its family, the expected mode is that of a typical nemacheilid: an egg-scatterer that releases eggs over gravel or among stones in fast-flowing water, with no parental care afterward. Set breeding.mode accordingly: egg-scatterer over gravel, no parental care, rarely bred.
As with the great majority of stone and brook loaches, this species is not known to have been bred in captivity. It is a poorly documented stream endemic rather than an established aquarium fish, and keepers should not expect to replicate a spawning event without first replicating the cool, fast, well-oxygenated flowing water its wild population depends on.
In the aquarium
Paracanthocobitis canicula is not an established part of the aquarium trade, and specific husbandry data is essentially absent from the literature. What can be said follows from its family and its native Mekong tributary habitat: this is a small (around 2.5 in), active, bottom-dwelling stream fish that would need strong water flow, high dissolved oxygen, and a substrate of stone, gravel and sand rather than a still, decorative setup.
Like other nemacheilids it is functionally near-scaleless, which makes it sensitive to copper-based medications and full-strength treatments generally — a half-dose, cautious approach is the safer default for any stone loach, this species included. Given how little is documented, anyone attempting to keep it should treat available information on its close relatives as a starting point rather than a confirmed care sheet, and should expect this to remain a specialist's fish rather than a mainstream one.
Conservation
Paracanthocobitis canicula has not been evaluated by the IUCN Red List. This is unsurprising for a small, recently described stream loach known from a limited number of localities in the Mekong basin — many such Southeast Asian stream endemics have never been formally assessed.
No population trend or specific threat data has been published for this species. In general terms, small Mekong tributary fishes of this kind face pressure from damming, sedimentation, deforestation and water extraction across the basin, but without a species-specific assessment it would be guesswork to attach a conservation status or a particular threat to Paracanthocobitis canicula. It is best treated as a data-deficient stream endemic pending further survey work.