Taxonomy & naming
Paracanthocobitis marmorata was formally described by Singer, Pfeiffer and Page in 2017 as part of a taxonomic revision of the Paracanthocobitis zonalternans species complex. That paper used both morphological characters and molecular (DNA) data to show that what had been treated as one widespread, variable species was in fact several, and it split out three new species — P. nigrolineata, P. marmorata and P. triangula — while also resurrecting P. phuketensis from synonymy. The holotype, a 1 in SL female, is deposited under the catalog number ZMA 119.972.
The genus Paracanthocobitis sits in the family Nemacheilidae, the stone and brook loaches, by far the largest loach family and one that has been extensively reshuffled in recent decades as older, broad genera such as Nemacheilus and Noemacheilus were split apart using modern taxonomic methods. Given how recently this species was named and how narrow its known range is, it remains poorly known outside the taxonomic literature, and no separate Catalog of Fishes correction or synonymy has altered the combination since its description.
Morphology
This is a small loach even by stone-loach standards: FishBase lists a maximum size of just 1.5 in standard length in females, making it one of the smallest fish covered in this atlas. It has the elongated, cylindrical body typical of Nemacheilidae, with the incomplete lateral line and largely scaleless or fine-scaled skin that characterizes the family.
The describing revision separates P. marmorata from its close relatives by a combination of fin-ray counts — 9½–10½ branched dorsal-fin rays and 8 branched upper caudal-fin rays — and the absence of an axillary pelvic lobe. Its common-name-worthy feature is pattern rather than size: a marbled arrangement of dark lines and blotches between the dorsal saddles, dark blotches running along the flank, and a distinctive teardrop-shaped black spot at the upper margin of the caudal-fin base, rather than the continuous black lateral stripe seen in some relatives. Like other nemacheilids it likely carries the small, erectile suborbital spine typical of the family, though this has not been specifically highlighted in the available descriptions.
Habitat
Paracanthocobitis marmorata is known from the Barak drainage in Assam, in India's northeastern hill country, with a type locality recorded at approximately 24.799°N, 93.782°E. The Barak is a fast-flowing river system draining the hills toward the Bay of Bengal via Bangladesh, and stone loaches of this genus are typically found in clear, well-oxygenated streams over rocky, pebbly or sandy bottoms with little aquatic vegetation.
As a Nemacheilidae species from a hill-country drainage, it fits the profile of the family's classic habitat: cool-to-moderate, fast, clear running water rather than warm, still, or blackwater conditions. Detailed environmental data specific to this species has not been published beyond the type-locality record, so its full seasonal and microhabitat range in the Barak system is not well documented.
Feeding
No feeding studies have been published specifically for Paracanthocobitis marmorata. Based on its close relatives in the genus — including the more widely known Paracanthocobitis botia, the mottled loach — stone loaches of this group are micro-predators that work the streambed for small invertebrates: insect larvae, small crustaceans and other tiny prey picked out of gravel and sediment in fast water.
In the aquarium, related Paracanthocobitis species take small live and frozen foods readily and may largely ignore dry flake, reflecting their natural preference for animal prey foraged off the bottom. Given the lack of species-specific data, the same expectation is the reasonable working assumption for P. marmorata, but this should be treated as inferred rather than confirmed.
Mating
Nothing specific has been published on courtship or spawning behaviour in Paracanthocobitis marmorata. The species was described from preserved museum material collected for taxonomic study, not from aquarium or field behavioural observation, and its recent description (2017) means it has had little time to accumulate hobbyist or research attention.
Across Nemacheilidae generally, stone and brook loaches are egg-scatterers rather than pair-spawners or cave-guarders, with no evidence of the elaborate courtship or parental behaviours seen in some other fish groups. In the absence of direct data for this species, that general family pattern is the best available guide, but no observations of P. marmorata itself in spawning condition have been documented.
Breeding
Paracanthocobitis marmorata has not been bred in the aquarium as far as published or hobbyist sources record. Stone and brook loaches of this genus are, where known, egg-scatterers that release eggs over gravel or among stones in fast-flowing water with no parental care — the pattern seen across Nemacheilidae generally — but confirmed home spawnings of this genus are rare even for its better-known relatives, and none have been documented for this species specifically.
Given its very recent description, tiny known range, and minimal presence in the aquarium trade, P. marmorata should be treated as effectively unbred in captivity. Any keeper who obtained this species would be working from first principles, informed mainly by what is known of its close relatives, rather than any established protocol.
In the aquarium
This species has essentially no aquarium track record — it is not a fixture of the loach trade, and specific husbandry accounts do not exist in the sources available. What can be said comes from its genus and family: as a small Nemacheilidae stone loach from a fast, clear hill stream, it would be expected to want cool-to-moderate, well-oxygenated, flowing water over a rocky or sandy substrate, similar to the conditions described for its relative Paracanthocobitis botia, which is generally kept around 61–79 °F in clear, current-rich setups with minimal planting.
As with virtually all Nemacheilidae, the near-scaleless skin typical of the family means caution is warranted with copper-based and full-strength medications if this species is ever kept and needs treatment. Because there is no confirmed supply chain, size reference beyond the 1.5 in maximum, or feeding/compatibility data specific to this fish, anyone encountering it in the trade should treat it as a data-sparse, specialist proposition rather than a mainstream community loach.
Conservation
Paracanthocobitis marmorata has not been evaluated by the IUCN Red List, so it carries no conservation category here — it is recorded as Not Evaluated rather than assigned a guessed status. Its very recent description (2017) and narrow known range in the Barak drainage of Assam mean that no population trend or threat assessment has been carried out.
Stream-restricted Nemacheilidae species like this one are, as a family, vulnerable in principle to the same pressures affecting South Asian hill streams generally — water diversion, siltation, and habitat degradation — but no species-specific data on threats, population size, or trend has been published for P. marmorata. It does not appear to be a species drawn into the aquarium trade in any meaningful volume, so aquarium collection is not documented as a pressure on it.