Taxonomy & naming
Desmopuntius endecanalis was described by Tyson R. Roberts in 1989 in his comprehensive account of the freshwater fishes of western Borneo (Memoranda of the California Academy of Sciences, vol. 14). The original combination was Puntius endecanalis Roberts, 1989, placing the species in the broadly defined old genus Puntius that then housed the majority of Asian barbs.
Following the far-reaching revision of Pethiyagoda et al. (2012) and subsequent reorganisation by Kottelat (2013), Asian barb genera were substantially restructured. The species was reassigned to Desmopuntius Kottelat, 2013 — a genus name derived from the Greek desmotes (prisoner, a reference to the barred pattern shared by its members, likened to a convict's stripes) combined with the parent name Puntius. More recently, the Catalog of Fishes records the valid combination as Desmopuntius endecanalis (Roberts, 1989), with the parenthetical authority reflecting the move from its original genus. The FishBase synonymy confirms Puntius endecanalis as the basionym and lists Desmopuntius endecanalis as a junior synonym of the current combination.
The species epithet endecanalis is Latin for "of eleven" (from Latin endecim, eleven, plus -alis) and refers to the characteristic number of anal-fin rays — a taxonomically useful meristic in a genus where species can appear superficially alike. The type locality is a small forest stream flowing into the Sungai Mandai in Kalimantan Barat, Borneo.
This fish was long listed as Systomus endecanalis; Eschmeyer's Catalog of Fishes places the species in Desmopuntius, and the current combination Desmopuntius endecanalis is followed here.
Morphology
Desmopuntius endecanalis is a small, moderately compressed barb reaching approximately 1.9 in standard length (around 1.77–1.97 in SL in well-grown specimens). Like other members of its lineage it carries a barred pattern — vertical dark bars over a pale body — which is the group character that gave Desmopuntius its "prisoner" etymology and which helps distinguish these species from the more uniform-sided barbs.
The diagnostic meristic feature is the count of branched anal-fin rays, which provided the species name: eleven (or a characteristic high count) distinguishes it from similar Bornean congeners in which ray counts differ. Scalation, fin placement and body depth follow the typical plan of small Southeast Asian barbs — short-bodied, with a single dorsal fin, paired pelvics set well back, and a forked tail. No striking sexual dichromatism has been recorded, though males of closely related species are generally slimmer and may show more intense colour when in spawning condition.
Habitat
The Kapuas River system of Kalimantan Barat (West Borneo, Indonesia) is the only confirmed range of Desmopuntius endecanalis. Within that basin the species occupies flooded forest along lake shores, peat swamps and small blackwater streams — the slow, heavily vegetated, humic-rich habitats that are characteristic of Sundaland's lowland freshwater landscape.
Water chemistry in these environments is extreme by the standards of most tropical fish: the blackwater of Bornean peat swamps is soft (total hardness often below 2° dGH), strongly humic-stained, and acidic, with pH values that can fall to 4.0 in intact swamp forest and may reach near-neutral (7.0) only where some dilution with mineral water occurs. Temperatures in Borneo's lowland streams are warm but can be somewhat variable — the Seriously Fish account documents a range of 66–79 °F for this species and its close relatives in similar habitats. Dissolved mineral content is very low, and the water carries abundant humic and fulvic acids from decomposing plant matter.
Desmopuntius endecanalis is described as benthopelagic — moving through the midwater and lower water column rather than being a strict bottom-dweller — and the species appears to associate with flooded forest margins where submerged leaf litter, root tangles and overhanging vegetation provide both cover and feeding opportunities.
Feeding
Desmopuntius endecanalis is classified as a micropredator: in the wild it takes small invertebrates including aquatic insects, worms and zooplankton from the water column and among leaf litter and submerged vegetation. This feeding guild is consistent with the species' small adult size and the invertebrate-rich peat-swamp environment it inhabits.
In aquaria, closely related Desmopuntius/Systomus species in the same feeding guild accept a range of small live and frozen foods — Daphnia, brine shrimp (Artemia nauplii), small bloodworm, and micro-pellets — and this species would be expected to behave similarly. A diet varied across multiple food types maintains condition; the species is not a herbivore or detritivore by primary inclination.
Mating
Like other barbs, Desmopuntius endecanalis is an egg-scattering, non-guarding spawner. There is no nest, no pair bond, and no parental investment beyond the act of spawning itself. When a gravid female and a conditioned male are ready, the male drives the female through fine-leaved vegetation or over the substrate in repeated pursuit sequences, and eggs and milt are released together in brief contacts.
The adhesive eggs fall among plants or onto the bottom. Adults — including the parents — will eat any eggs they encounter, and no territory or clutch defence takes place. Colour and activity intensity in males typically peaks at spawning time, reflecting competition among males for access to ripe females in a schooling species.
Breeding
Desmopuntius endecanalis has not been widely documented in captive breeding. Based on its ecology and the reproductive biology shared across the barb family, breeding attempts would follow the egg-scatterer protocol: soft, warm, acidic water (pH 4.5–6.5, temperature around 75–79 °F) closely replicating the blackwater conditions of its native peat swamps, with fine-leaved plants or spawning mops to catch the adhesive eggs, and removal of adults immediately after spawning to prevent egg predation.
Fecundity in small barbs of this size is typically in the low to mid hundreds of eggs per spawning event. Eggs in soft warm water hatch within one to two days, and larvae become free-swimming a few days later. First foods for fry would be infusoria-sized items or commercial fry foods, transitioning to newly hatched brine shrimp as the fish grow. The rarity of the species in the trade means captive-breeding records are sparse, and specific husbandry refinements have not been widely published.
In the aquarium
Desmopuntius endecanalis is a rarely exported species; it is not a common aquarium fish, and most aquarists will encounter it only through specialist importers of Bornean blackwater fauna. When available, its care requirements centre on replicating the soft, acidic, humic-stained waters of its native peat swamps. Very soft water (near-zero hardness, pH 4.5–6.5), warm temperatures (72–79 °F), and dark-stained conditions with leaf litter, driftwood and subdued lighting suit the species well.
As a schooling micropredator reaching under 2 in, Desmopuntius endecanalis is best kept in groups of six or more with peaceful, similarly sized companions that share its water-chemistry preferences — other small Bornean blackwater species are ideal. It poses no threat to fish its own size but would readily consume very small fry. The species' small size and preference for pristine, soft acidic water make it unsuitable for hard-water or heavily stocked community set-ups. Water quality must be excellent, as peat-swamp species can be sensitive to dissolved waste, though filtration through peat or the use of Indian almond leaves helps approximate the humic chemistry of its natural environment.
Conservation
Desmopuntius endecanalis is assessed as Data Deficient (DD) on the IUCN Red List, evaluated on 30 March 2020. The Data Deficient rating reflects a genuine gap in the available information: the species is known from the Kapuas River basin of Kalimantan Barat, but distribution data within that basin are limited, and population size and trends have not been adequately assessed.
The peat-swamp and flooded-forest habitats that Desmopuntius endecanalis occupies are among the most threatened freshwater environments in Southeast Asia. Indonesian Borneo has experienced extensive peat-swamp drainage for palm oil and timber plantations, compounded by recurrent peat fires and conversion of floodplain forest. The small, soft-water streams and swamp margins that blackwater species depend on are particularly vulnerable to drainage, agricultural runoff and changes in hydrology. A species endemic to a single river basin in a region undergoing rapid land-use change warrants precautionary concern even in the absence of quantified population data, and future reassessment with targeted survey effort in the Kapuas basin is needed to determine its true status.