Taxonomy & naming
Paraschistura delvarii was described in 2015 by Hamid Reza Mousavi-Sabet and Soheil Eagderi, two Iranian ichthyologists who have described a number of the country's endemic stream loaches. It belongs to the family Nemacheilidae, the stone or brook loaches — by species count the largest loach family, made up mostly of small, slender fishes confined to single river drainages across Eurasia. The genus Paraschistura is one of several segregate genera carved out of the old, unwieldy "Nemacheilus"/"Noemacheilus" catch-all as the family was progressively revised through molecular and morphological work; related genera from the same region include Schistura, Oxynoemacheilus and Paracobitis.
The species epithet honours the type locality area, and the Catalog of Fishes — the standard authority for valid fish names — lists it as Paraschistura delvarii within Nemacheilidae. No synonyms or subsequent taxonomic changes are documented in the sources consulted here; it appears to be a stable, recently described, narrowly endemic species.
Morphology
This is a small fish even by stone-loach standards. Type and voucher specimens measured in the original description and subsequent osteological work run around 1.5 in standard length, and FishBase gives a maximum size of about 1.5 in SL — this is a fish that could sit comfortably on a fingertip. Like other Nemacheilidae it has an elongate, slightly compressed body, a small subterminal mouth suited to picking food off the streambed, and paired barbels around the mouth for feeling out prey in the substrate.
As in other true loaches, the skin carries only tiny, deeply embedded scales, leaving it functionally near-scaleless — a point that matters for its sensitivity to medication and disease, discussed further under In the aquarium. Where the family's diagnostic erectile suborbital spine has been documented in related Paraschistura and Schistura species it is present as a small defensive spine beneath the eye; detailed colour-pattern and fin-ray counts for this species are not covered in the sources available here, so we do not attempt to describe them from memory.
Habitat
Paraschistura delvarii is known only from the upstream tributaries of the Gharaghaj River, part of the Mond River drainage in Fars province, southern Iran — a Persian Gulf basin system. FishBase classifies it as a subtropical, freshwater, benthopelagic species, consistent with the small, clear, flowing headwater streams typical of Nemacheilidae habitat across the Iranian plateau and Zagros foothills: cool-to-warm running water over stone, gravel and sand, with the current keeping the water well oxygenated.
No other locality has been reported for the species, which is consistent with the classic Nemacheilidae pattern of single-drainage endemism seen across Iran, Anatolia and Central Asia. Precise seasonal or depth data are not available in the sources reviewed, so this should be read as a general habitat picture rather than a site-specific one.
Feeding
FishBase records a trophic level of about 2.9 for this species, which places it as feeding low on the food web, primarily on algae, detritus and fine organic material picked from the stream bed and rock surfaces, likely supplemented with small invertebrates as in most of its relatives. This fits the general Nemacheilidae pattern of grazing and micro-predation on the substrate of fast, clear streams rather than active mid-water hunting.
No specific dietary studies or aquarium feeding reports exist for this species in the sources consulted. A keeper attempting to house it — should material ever become available — should assume it needs a mix of algae/biofilm grazing opportunity plus small sinking live, frozen or micro-pellet foods, in line with its relatives, rather than flake fed at the surface.
Mating
No courtship or spawning behaviour has been documented for Paraschistura delvarii in the sources reviewed here. Nothing is published on sexual dimorphism, pairing behaviour or spawning triggers for this species specifically. In the absence of direct data, the family pattern for Nemacheilidae is the best guide: stone and brook loaches typically show little obvious external dimorphism, and spawning is generally associated with rising flow and cooler, oxygen-rich water rather than any elaborate courtship.
Breeding
There is no record of Paraschistura delvarii being bred in captivity, and it does not appear to have entered the aquarium trade at all — it is known purely from scientific collections in its home drainage. Based on the well-documented pattern across Nemacheilidae, the honest expectation is an egg-scatterer that releases eggs over gravel or among stones in fast-flowing water, with no parental care; stone and brook loaches as a family are rarely if ever bred in home aquaria, and most, like this one, are simply too poorly known and too narrowly distributed for any breeding data to exist.
Given the complete absence of trade or hobby history, this section should be read as informed inference from the family's biology rather than as observed fact for the species itself.
In the aquarium
Paraschistura delvarii is not known to be present in the aquarium hobby; there is no trade history, no care reports, and no evidence it has ever left its native drainage alive for the ornamental market. This profile exists to document the species, not to recommend it as a fishkeeping subject.
Were it ever to appear, the sensible starting point would follow the general rules for small Nemacheilidae stone loaches: cool-to-moderate, clean, well-oxygenated, flowing water over a fine gravel or sand substrate, since this is a fast-stream endemic rather than a still-water fish. Like other true loaches it is likely near-scaleless and therefore sensitive to copper-based medications and full-strength treatments, so any future keeper should treat it — and any tankmates showing disease — with particular caution and reduced dosing.
Conservation
Paraschistura delvarii has not been evaluated by the IUCN Red List, so it carries no conservation category here — we record it as Not Evaluated rather than assign a status without an assessment. As a species known from a single river drainage in the Mond River system of Fars province, Iran, it fits the broader pattern of narrow-range stream endemics across the Iranian plateau, a region where water extraction, damming and drought pressure on freshwater systems are ongoing concerns for many similarly localized fishes.
There is no evidence in the sources reviewed of any aquarium-trade collection pressure on this species — it does not appear to be traded — so any conservation concern would stem from habitat and water-use pressures on its home drainage rather than from ornamental collecting.