Taxonomy & naming
Paracanthocobitis abutwebi was described by Rupert Collins Singer and Lawrence Page in 2015, in a revision of the zipper loach genera Acanthocobitis and Paracanthocobitis published in the journal Copeia (103(2): 378–401). The genus Paracanthocobitis itself is a relatively recent split from the older, broader Nemacheilus/Noemacheilus and Acanthocobitis groupings — a reshuffling typical of this family, where the Catalog of Fishes governs which combination is currently valid and species have moved between genera more than once as the group has been revised.
The species belongs to Nemacheilidae, the stone or brook loaches, by far the largest family of true loaches and one still being actively worked through by taxonomists. The specific epithet abutwebi honours Professor Abu Tweb Abu Ahmed. No older combination is in wide use for this species — it was named directly into Paracanthocobitis and has not been shuffled since.
Morphology
This is a small, slender stone loach, reported to reach only about 2 in in standard length — a genuinely tiny fish even by nemacheilid standards. It has a complete lateral line and lacks an axillary pelvic lobe. Its most distinctive feature is the pattern that gives the zipper loaches their name: a row of alternating large and small dark spots running along the lateral line, paired with dark specks scattered on the upper flank between a series of small dorsal saddles. The caudal fin carries four to five dark bands, and the fin-ray counts are typical for the genus — usually 11 dorsal-fin rays and 13 pectoral-fin rays.
Like other nemacheilids it has an erectile suborbital spine and skin that is functionally naked, the scales being tiny and deeply embedded rather than forming an obvious armour. Beyond the original description, detailed morphological data — growth curves, exact scale counts across populations, colour variation — has not been compiled; this is a data-sparse species outside its taxonomic paper.
Habitat
Paracanthocobitis abutwebi is endemic to Bangladesh, known from the Karnaphuli, Meghna, lower Brahmaputra and Ganges river drainages. Its type locality is a small creek — Rangapani Khal — in the Meghna basin near Sylhet, in the northeast of the country. As a stone loach it is presumed to occupy the clear, flowing, well-oxygenated headwater and tributary streams typical of the family, over sand, gravel or rocky substrate, though a detailed habitat account has not been published for this particular species.
Available sources describe it as a small stream specialist with sparse ecological data. Given its family and its Bangladesh drainage context, cool-to-moderate, well-aerated flowing water is the reasonable expectation rather than warm, still, blackwater conditions — but specific temperature and chemistry readings from its native streams have not been recorded in the literature consulted here.
Feeding
No dedicated dietary study of Paracanthocobitis abutwebi has been located. As with other stone loaches in Nemacheilidae, it is reasonable to expect it forages as a micro-predator over the streambed, picking small invertebrates — insect larvae and tiny crustaceans — from among sand, gravel and stones in fast-flowing water, but this is inferred from family-level biology rather than confirmed for the species itself.
In a hypothetical aquarium setting, a nemacheilid of this size and habitat would be expected to take small live and frozen foods such as bloodworm and daphnia readily, and sinking foods generally, with less interest in flake left at the surface. No hobby feeding reports for this species exist to confirm the point.
Mating
Nothing specific has been published on courtship, sexual dimorphism or spawning behaviour in Paracanthocobitis abutwebi. This is unsurprising for a species known essentially from its original taxonomic description and a handful of database records — the reproductive biology of most Nemacheilidae species, especially recently described, range-restricted ones, remains undocumented.
By analogy with better-studied stone and brook loaches, egg-scattering in fast-flowing water with no courtship display or pair bonding beyond the spawning act itself would be the expected pattern, but this has not been observed or recorded for this species specifically.
Breeding
There is no record of Paracanthocobitis abutwebi being bred in captivity. Stone and brook loaches as a group are egg-scatterers, releasing eggs over gravel or among stones in fast-flowing water with no parental care, and they are rarely bred in home aquaria even where the species is well established in the hobby — most nemacheilids are simply not aquarium staples in the way corydoras or many characins are.
Given that this species is barely present in the trade or hobby literature at all, breeding.mode is best described plainly: presumed egg-scatterer over gravel with no parental care, following the pattern for its family, but with no confirmed spawning reports of any kind. Data here is sparse to the point of nonexistence beyond the taxonomic description.
In the aquarium
Paracanthocobitis abutwebi is not established in the ornamental trade and has no meaningful aquarium-keeping literature. Anyone encountering it would need to treat it with the general caution due any small nemacheilid stone loach: cool-to-moderate, clean, well-oxygenated, flowing water over a soft sand or fine gravel substrate, since these are stream fish rather than still-water fish, and a tank scaled to its very small adult size of roughly 2 in.
As with virtually all true loaches, its skin is functionally scaleless, which makes it sensitive to copper-based and full-strength medications generally — half-doses and gentle treatment are the safe default for the family. Given how little is documented about this specific species, anyone keeping it would be working from family-level inference rather than species-specific guidance, and should treat any specimens as a conservation-sensitive, poorly known stream endemic rather than a routine community fish.
Conservation
Paracanthocobitis abutwebi has not been assessed on the IUCN Red List and is recorded here as Not Evaluated rather than assigned a guessed status. As a range-restricted endemic known only from a handful of drainages in Bangladesh, and a species whose ecological requirements are described as sparsely documented even by the regional biodiversity literature, it fits the broader pattern of small-range nemacheilid stream loaches that have simply never been formally reviewed for conservation status.
No information on population trend, habitat pressure or trade collection has been located for this species. Its native streams in the Karnaphuli, Meghna, Brahmaputra and Ganges drainages of Bangladesh are part of a densely populated and heavily used river system, so habitat degradation is a plausible general risk for small stream specialists in the region, but no documented assessment exists to confirm or quantify it for this species.