Taxonomy & naming
Rasbora arundinata was formally described by Lumbantobing in 2014 as one of four new species of the Sumatrana group, a clade of slender Sumatran rasboras united by a black midlateral band running from the snout to the caudal-fin base. The Catalog of Fishes (Eschmeyer, CAS — the authority for valid names) records the species under Rasbora Bleeker, 1859, where it remains; no subsequent revisionary transfer has been proposed.
The Sumatrana group is distinguished from other Rasbora assemblages by the extent and form of the dark lateral stripe and by various meristic characters. Lumbantobing's 2014 revision placed R. arundinata as allopatric to its congeners, occupying the northwestern coastal drainages of Sumatra (Aceh Province) rather than the central or southern Sumatran rivers used by the other Sumatrana group members.
The genus Rasbora itself remains large and almost certainly polyphyletic — multiple authors have carved out Boraras, Trigonopoma, Brevibora, Kottelatia and Rasboroides from what was once a catch-all assemblage. R. arundinata has not been reassigned to any of these segregate genera, and no molecular phylogenetic placement beyond the Sumatrana group has been published.
Morphology
R. arundinata is a small, elongate rasbora. FishBase records males at 1.5–5 in standard length (SL) and females at 2–5.5 in SL, though most adults in field samples fall below 3 in SL; the figure of 5.5 in likely captures exceptional individuals. The body is slender and fusiform, typical of the Sumatrana group.
The most distinctive feature is the black midlateral stripe, which runs continuously from the snout tip to the tip of the caudal fin and broadens and tapers in a way that resembles the profile of a reed leaf — the character that inspired the specific epithet. This stripe is more sharply defined and more prominent than in some congeners, aiding field identification within the Sumatrana group. Fin coloration and body depth details are documented in Lumbantobing's original description. Sexual dimorphism in body depth is likely present (females deeper-bodied when gravid) as in related species.
Habitat
The species is documented from three river systems in the northwestern coastal zone of Sumatra: the Tripa Jaya, Kluet and Alas rivers, all within Aceh Province, Indonesia. These are geographically restricted allopatric populations; the species has not been recorded from the major central or southern Sumatran drainages occupied by other Sumatrana group members.
FishBase records habitat as gravel-bottomed mountain streams, moderate-flowing turbid rivers and muddy backwater pools — a range that spans both fast, clear highland reaches and lower, more turbid sections as the rivers descend toward the coast. The 2024 reproductive study documented the species in the Krueng Lanca River, a smaller tributary in Nagan Raya District, Aceh, confirming its occurrence in mid-gradient streams with moderate current.
Water chemistry specific to R. arundinata's habitat has not been published in detail, but Sumatran coastal rivers in Aceh tend toward soft, mildly acidic conditions, with conductivity and pH rising in lowland reaches. General values for Sumatran rasbora habitats (pH 6.0–7.0, soft water) serve as a reasonable approximation until site-specific data become available.
Feeding
No dedicated dietary study of R. arundinata has been published. As a member of the genus Rasbora, it is expected to be an opportunistic omnivore in the wild, taking small invertebrates — aquatic insect larvae, microcrustaceans and similar items — from the water column, supplemented by terrestrial insects and organic detritus washed into the stream. The elongate body and mid-water swimming posture are consistent with an active pursuit feeder in the stream column.
In the aquarium, Rasbora species of this size accept standard small-particle foods: quality flakes, micro-pellets and live or frozen Daphnia, bloodworm and brine shrimp. Feeding a variety of foods supports condition and natural coloration.
Mating
R. arundinata has not been bred under aquarium conditions with a published account, but as a member of Rasbora it is an egg-scattering, non-guarding spawner. Courtship follows the typical Rasbora pattern: a ripe male pursues a gravid female through the vegetation or open water of a stream margin, pressing alongside her briefly as eggs and milt are released together.
There is no pair bond, no nest and no territory. Spawning is cued by seasonal conditions in the wild — likely tied to rainfall and stream-flow changes in the monsoonal Aceh rivers — and adults pay no attention to the eggs once they have been shed. The small, adhesive eggs sink or catch on substrate and vegetation.
Breeding
No captive breeding account specific to R. arundinata has been published; the following is based on the standard Rasbora egg-scatterer model. A separate, densely planted spawning vessel with fine-leaved plants or a clump of Java moss provides cover for spawning and places for eggs to lodge out of the adults' reach. Conditioning the pair or small group on live and frozen foods for several days prior typically prompts spawning.
Eggs are adhesive and scattered over plants and substrate. Because adults will consume eggs readily, removing spawning fish promptly after observation of spawning is advisable. Eggs hatch in approximately two to three days at tropical temperatures; larvae become free-swimming within a few more days and can be started on infusoria or commercial fry foods, transitioning to newly hatched brine shrimp as they grow. Parental care is absent at all stages.
In the aquarium
R. arundinata is rarely encountered in the aquarium trade; it is a recently described species with a narrow range and no established captive-breeding program. Any specimens that do reach hobbyists will be wild-caught from Sumatran rivers, which places both a welfare responsibility on the keeper and a conservation consideration given the species' restricted distribution.
For those who obtain it, care should follow the model for other medium-sized Sumatrana group rasboras: a longer aquarium with moderate flow, well-planted with room to swim, soft to moderately soft water at a mildly acidic to neutral pH (approximately 6.0–7.0), and water temperature in the tropical range consistent with Sumatran rivers. As a schooling fish it should be kept in groups. A varied diet of quality dry foods supplemented with live or frozen invertebrates supports condition.
Conservation
R. arundinata has not been assessed by the IUCN Red List. Described only in 2014, it falls into a large cohort of recently named Southeast Asian freshwater fishes that have not yet been formally evaluated. On current evidence the species is Not Evaluated (NE).
The conservation outlook warrants attention nonetheless. R. arundinata is known only from three river drainages in Aceh Province, a restricted distribution that makes any localized threat potentially significant at the species level. The 2024 reproductive study in the Krueng Lanca River confirms current presence in Nagan Raya District but also highlights the species as highly localized. Sumatran freshwater habitats face ongoing pressures from agricultural expansion (including oil-palm plantations), sedimentation, water extraction for irrigation and localized pollution from smallholder and industrial activity. Formal IUCN assessment of R. arundinata would be a useful first step toward understanding its status.