Taxonomy & naming
Rasbora tuberculata was described by Maurice Kottelat in 1995 in the Raffles Bulletin of Zoology 43(1):51–64, the same paper that established or redefined several small Bornean and Southeast Asian cyprinids. The species epithet tuberculata refers to small tubercles or nodular features observed in the type material — a descriptive Latin adjective from tuberculum, a small swelling or knob. The holotype is deposited at the Museum Zoologicum Bogoriense (MZB 5902), Jakarta.
The genus Rasbora is a large, historically heterogeneous assemblage that has seen significant revision since the 1990s. Kottelat and Witte (1999) carved out Trigonostigma, Boraras, Trigonopoma and other genera; Brevibora, Kottelatia and Rasboroides have followed as additional segregates. Rasbora tuberculata has not been proposed for transfer and the Catalog of Fishes retains it in Rasbora. No synonyms are recorded and there is no subspecific division.
Morphology
R. tuberculata is a very small fish, with a maximum recorded standard length of 1 in according to FishBase. Like most members of the genus it is laterally compressed and fusiform, built for life in a water column that alternates between still pool and moderate riffle. The species was described on the basis of specific meristic and morphometric characters — counts of scale rows, fin-ray formulae and proportional measurements — that distinguish it from the many other small Bornean Rasbora that inhabit the same drainage.
Detailed colouration in live individuals is not well documented in the literature, partly because the species has rarely been collected in any quantity since the original description. Preserved material shows the pale, slightly translucent body typical of many small, hill-stream rasboras of Sundaland, with patterning that may be visible only in fresh or live specimens under good lighting. Data on external sexual dimorphism are sparse.
Habitat
The IUCN assessment for R. tuberculata, completed in January 2019, describes the species as inhabiting clear, slow to swift water in small creeks in hilly areas, with habitat including both riffles and deeper pools. The type locality, Sungai Pala at Pala Hulu, lies at approximately 0°21'42"N, 111°55'47"E in the Kapuas basin of Kalimantan Barat — a watershed that drains a large portion of the interior of Borneo through a complex of tributaries before reaching the South China Sea.
The hill-creek character of its habitat sets it apart from the blackwater peat-swamp species of the Sundaland lowlands. The water is described as clear rather than tannin-stained, suggesting mineral substrates in hilly terrain rather than the humic, acidic conditions of the lowland peat swamps. General data for hill-stream Rasbora of Borneo suggest soft to moderately soft, slightly acidic to neutral water with temperatures in the tropical range, though species-specific measurements for R. tuberculata are not published.
Feeding
No species-specific dietary data have been published for Rasbora tuberculata. By analogy with other small, insectivorous Rasbora of Bornean hill streams, it almost certainly takes small invertebrates — aquatic insect larvae, microcrustaceans and similarly scaled prey — from the water column and substrate surface, supplemented opportunistically with fine organic material.
In the aquarium, small rasboras of this type typically accept fine-grade commercial foods but thrive best on a mixed diet weighted toward live and frozen items such as micro-worms, newly hatched brine shrimp and daphnia, which match the invertebrate prey of their natural environment.
Mating
No published observations of reproductive behaviour exist for R. tuberculata specifically. As a member of the genus Rasbora, it is expected to follow the egg-scattering pattern characteristic of the group: a driving male pursues a gravid female through fine-leaved vegetation or over a gravel or sandy substrate, and eggs and milt are released together in brief pressing contacts. There is no pair bond, no nest construction and no parental care of any kind.
Spawning is likely triggered by seasonal cues — shifts in water level, temperature or photoperiod associated with the onset of the wet season in Borneo — although the precise triggers have not been studied in this species.
Breeding
Rasbora tuberculata has not been bred in captivity under documented conditions. Should it become available to hobbyists, standard small-rasbora practice would apply: a planted spawning vessel with fine-leaved plants or a Java moss mat over an open base, soft slightly acidic water in the tropical range, and well-conditioned adults introduced in small groups. Eggs would be expected to be adhesive to weakly adhesive and scattered among vegetation or allowed to fall to the substrate, where adults would consume them if not removed.
Given its hill-creek origin, slightly cooler and well-oxygenated conditions may prove beneficial relative to the warmer blackwater conditions suited to lowland peat-swamp rasboras. Fry would be expected to be small and initially require infusoria or commercial micro-fry foods before graduating to newly hatched brine shrimp.
In the aquarium
Rasbora tuberculata is not a species currently established in the aquarium trade and is essentially unknown in the hobby. It appears in no standard hobbyist catalogues or trade lists, and has not been imported as a commercial item as far as the published record shows. This is unsurprising given that it is known from a single brief collecting event at its type locality and has not been the subject of further ichthyological fieldwork.
For aquarists who might encounter it through specialist importers or scientific collections, its small size, clear-water hill-creek origin and expected delicacy would place it firmly in the category of a specialist fish — best suited to a quiet, species or near-species tank with soft, slightly acidic, well-oxygenated water, fine substrate, live foods and no boisterous tankmates. Its tiny size at under 1 in SL demands attention to water quality and appropriate companions.
Conservation
The IUCN Red List assesses Rasbora tuberculata as Data Deficient (DD), with the assessment published on 7 January 2019. The designation reflects a genuine lack of survey data rather than a finding of security: the species is known from a single type locality in the Kapuas basin and has not been systematically re-surveyed since its 1995 description, leaving its true population size, distribution extent and trend unknown.
The Kapuas basin of Kalimantan Barat is subject to ongoing and accelerating pressures — deforestation for palm oil and timber, agricultural runoff, artisanal and industrial gold mining (a significant source of mercury contamination in Kalimantan streams), and the sedimentation of clear hill-creek systems. Small, narrow-range species in such habitats are inherently vulnerable even before a formal decline is documented. More field survey work is needed to determine whether R. tuberculata persists at its type locality and whether it occurs elsewhere in the Kapuas system.