Taxonomy & naming
Homatula longidorsalis was described in 1994 by Yang, Chen and Kottelat, placing it in the stone-loach family Nemacheilidae, order Cypriniformes. Nemacheilidae is the largest of the loach families and has been repeatedly reshuffled as ichthyologists split the old catch-all genera Nemacheilus and Noemacheilus; Homatula is one of the resulting Chinese and Southeast Asian genera that absorbed a share of those species. The Catalog of Fishes (Eschmeyer, CAS) is the authority for the valid combination, and it remains listed as Homatula longidorsalis.
The species epithet longidorsalis is descriptive Latin — 'long-dorsal' — for the elongated dorsal-fin base that distinguishes it from close congeners. FishBase separates it from Homatula berezowskii and Homatula variegata by a combination of head length, caudal-peduncle depth, the length of the dorsal adipose crest, the extent of body squamation, and details of intestinal coiling — the kind of fine anatomical work typical of Nemacheilidae taxonomy, where many species are told apart only by such measurements rather than obvious colour differences.
Morphology
Homatula longidorsalis is a small, elongate stone loach reaching about 3.5 in in standard length. Its defining feature, as the name promises, is a long-based dorsal fin — reported at more than 20% of standard length — carried on a slender body with a low, elongated dorsal profile. FishBase records eight dorsal rays. Like other Nemacheilidae it is functionally scaleless to the eye, the flanks bearing only tiny, deeply embedded scales, leaving the skin exposed in the way typical of the family.
As in related stone loaches, an erectile suborbital spine sits in a groove beneath each eye — a defensive structure the fish can flick out, and one worth handling with care when netting or moving the fish. Between the near-naked skin and this spine, Homatula longidorsalis shares the two anatomical hallmarks that run through the whole stone-and-brook-loach group.
Habitat
This species is known only from the Yangtze River drainage in China, where FishBase records it as a freshwater, demersal fish. The Yangtze's upland tributaries are cool, fast-flowing and well-oxygenated, fed by mountain drainage rather than lowland swamp, and Nemacheilidae in these systems are typically found over clean gravel, sand and stone substrate in riffle habitat with moderate to strong current.
No specific temperature or pH readings for this species have been published, but its Yangtze-tributary range points to the same clear, cool, oxygen-rich running water that the wider stone-loach family depends on — not the warm, still, blackwater conditions associated with lowland tropical fish. Given the sparse published record, its exact stream and elevation within the drainage are not documented, and it should be treated as a narrow-range habitat specialist rather than a generalist.
Feeding
FishBase places Homatula longidorsalis at a trophic level of about 2.7, consistent with a benthic micro-predator that forages low on the food web — the pattern typical of Nemacheilidae, which pick small aquatic invertebrates, insect larvae and tiny crustaceans off gravel and stone in fast water rather than grazing algae or taking large prey.
No aquarium feeding record exists for this species, but going by its family it would be expected to take small live and frozen foods such as bloodworm and daphnia readily, sift sinking foods from the substrate, and largely ignore food left floating at the surface — a fish that feeds down in the current, not up in the water column.
Mating
No courtship or spawning behaviour has been documented for Homatula longidorsalis specifically. External sexual dimorphism has not been described for this species either; the original description is a taxonomic account rather than a behavioural one, and nothing further appears to have been published since.
Based on the wider Nemacheilidae family, to which the closely related European stone loach (Barbatula barbatula) also belongs, mating in this group centres on spawning migrations into shallow, fast-flowing riffle habitat, where ripe fish release eggs directly into the current rather than pairing off or defending territory.
Breeding
Data on breeding is sparse for this species and no husbandry records or aquarium spawnings appear to be documented. Going by its family, Homatula longidorsalis would be expected to be an egg-scatterer: Nemacheilidae typically spawn over gravel, sand and vegetation in fast-flowing riffles, producing large numbers of small sticky eggs that adhere to the substrate, with no parental care afterward.
As with the great majority of stone and brook loaches, there is no record of this species being bred in the home aquarium. It should be assumed unbred in captivity, and any keeper attempting it would be working from family-level inference rather than a known protocol.
In the aquarium
Homatula longidorsalis has essentially no footprint in the aquarium hobby — it is a narrow-range Chinese endemic with no significant trade presence, and this profile is built from its scientific description rather than from keeper experience. Any specimen encountered in the hobby should be treated as a genuine stone-loach specialist: cool-to-moderate, clear, well-oxygenated, flowing water over a gravel or sand substrate, with strong filtration to replicate current.
Like other Nemacheilidae it is likely near-scaleless and correspondingly sensitive to copper-based medications and full-strength treatments generally; any medicating should start conservative. At around 3.5 in it is a modest-sized fish, but with no aquarium record to draw on, tank size, social needs and compatibility should be approached cautiously rather than assumed from more commonly kept relatives.
Conservation
Homatula longidorsalis has not been formally assessed on the IUCN Red List and is recorded here as Not Evaluated. No population trend, threat assessment or abundance data appear to exist in the published literature for this species.
As a narrow-range endemic confined to the Yangtze River drainage, it sits in a system under well-documented pressure from damming, water extraction and habitat modification across Chinese river basins generally — but without a species-specific assessment, no conservation status or trend can be honestly claimed beyond that general context. This is a data-sparse species in every sense, known essentially from its original description.