Taxonomy & naming
The species was described in 1971 by Mathur and Yazdani as Noemacheilus rajasthanica (some sources give 1970 for the original publication), placing it in the old, broadly-defined genus Noemacheilus that once held the great majority of Asian stone loaches. As with most of that assemblage, subsequent revision of the Cobitoidea split Noemacheilus into a set of narrower genera, and the species is now carried under Schistura rajasthanica — the combination used by the Catalog of Fishes, the standing authority for valid fish names.
It belongs to the family Nemacheilidae, the stone or brook loaches, by far the largest family in the loach superfamily Cobitoidea, and to the genus Schistura, an enormous genus of small benthic stream loaches distributed across South, Southeast and East Asia. The species epithet rajasthanica refers directly to Rajasthan, the Indian state where it was collected and described, marking it as a narrow-range regional endemic rather than a widespread member of the genus.
Morphology
Detailed morphological data for Schistura rajasthanica is not available from the sources consulted for this profile, and no aquarium or ichthyological photograph reference could be confirmed. What can be said with confidence follows from its placement in Schistura and Nemacheilidae: it is a small, elongate, laterally compact loach with a rounded, non-flattened cross-section typical of stone loaches (as opposed to the dorsoventrally flattened body of a true hillstream loach), a subterminal mouth suited to picking food from the substrate, and the near-scaleless, delicate skin shared across the family, which makes the group sensitive to poor water quality and to strong medications.
Like other Schistura it likely carries the small, erectile suborbital spine characteristic of the loach superfamily Cobitoidea, tucked in a groove below the eye and used defensively rather than offensively. Without a confirmed size record for this species, no maximum length figure is given here rather than guessed at; congeneric brook loaches in this size class are typically modest, in the range of a few centimetres.
Habitat
Schistura rajasthanica is endemic to a stream system in Rajasthan, in northwestern India — a distribution that places it at something of a geographic outlier for the genus, which is centred further east and south across the wetter hill and mountain drainages of the Indian subcontinent and Southeast Asia. As a narrow-range endemic known from a limited area, it fits the pattern common across small-stream Schistura: a species tied tightly to one drainage, with no confirmed presence elsewhere.
No site-specific habitat description for this species was found in the sources consulted, but its family and genus placement point strongly to a clear, flowing stream over gravel or rock, cool to moderately warm and well-oxygenated — the standard Schistura habitat template. Closely related Schistura species (S. nilgiriensis, S. mahnerti, S. denisonii, S. spilota) are documented in cool, fast-flowing, well-oxygenated clear streams with temperatures around 64–79 °F, and that range is used here as a reasonable, clearly-labelled inference rather than a confirmed reading for S. rajasthanica itself.
Feeding
No feeding data specific to Schistura rajasthanica was found. Based on its genus and family, it is almost certainly a benthic micro-predator, working the stream bottom for small invertebrates — insect larvae, small crustaceans and other invertebrate prey — in the manner typical of Nemacheilidae. This is an inference from the genus rather than a documented observation for this particular species.
In an aquarium setting a fish of this type would be expected to take small live and frozen foods such as bloodworm and daphnia readily, along with sinking pellets formulated for bottom-feeders, and to show little interest in flake left to drift at the surface — again following the well-documented pattern for small stream-dwelling Schistura rather than any record specific to this species.
Mating
Nothing specific to Schistura rajasthanica has been documented on courtship, sexing or spawning behaviour, and no aquarium reports exist to draw on. Stone and brook loaches in general are egg-scatterers with no pair bond and no nest — ripe adults release eggs over gravel or among stones in flowing water and take no further part — and there is no reason from its genus placement to expect this species to differ.
External sexual dimorphism has not been documented for this species; in Nemacheilidae generally it tends to be subtle at best, sometimes limited to a plumper body in gravid females, and cannot be assumed here without direct observation.
Breeding
Schistura rajasthanica has not been recorded breeding in captivity, and given how little is documented about the species even in the wild, this is unsurprising rather than notable. Its expected breeding mode, following the pattern for stone and brook loaches generally, is that of an egg-scatterer: eggs are released over gravel or among stones in fast-flowing water, fertilised externally, and left to develop with no parental care whatsoever.
This is the honest picture for the great majority of Nemacheilidae — most stone and brook loaches, including this one, are simply not bred in home aquaria, and there is no aquarium-trade or hobbyist record of Schistura rajasthanica being kept, let alone spawned. Any claim of a specific spawning trigger or fecundity for this species would be invented rather than sourced, so none is given.
In the aquarium
Schistura rajasthanica does not appear to be part of the aquarium trade — it was not found on FishBase's public species pages nor on Seriously Fish, and no hobbyist keeping reports were located. It should be treated as a fish essentially unknown to the hobby rather than a species with an established care template.
Were it ever encountered, general Nemacheilidae care principles would apply: cool-to-moderate, clean, fast-flowing, well-oxygenated water over a gravel or rocky substrate, since this is a stream specialist rather than a still-water fish; a scaleless skin sensitive to copper and to full-strength medication, calling for the gentler, reduced-dose treatment approach used across the loach family generally; and a diet of small sinking invertebrate foods rather than flake. These are inferences drawn from its genus and family, not documented husbandry for this species specifically, and are offered as a starting template only.
Conservation
Schistura rajasthanica has not been evaluated on the IUCN Red List and carries no formal conservation status. As a narrow-range endemic known only from a stream system in Rajasthan, it fits the pattern common to many small-stream Schistura across South Asia — species with restricted, poorly-surveyed distributions that have simply never been assessed, rather than species confirmed to be secure.
No specific threats to this species have been documented in the sources consulted. In general terms, narrow-range stream endemics in Rajasthan and similar semi-arid regions of India face pressure from water extraction, damming and habitat alteration of the limited perennial stream habitat available in drier parts of the subcontinent, but without a dedicated assessment for this species, that remains a general regional concern rather than a documented finding for Schistura rajasthanica itself.