Taxonomy & naming
Odontostilbe splendida was described by Lucia Bührnheim and Luiz R. Malabarba in a 2007 paper published in Neotropical Ichthyology (volume 5, number 1, pages 1–20), the same work that simultaneously redescribed Odontostilbe pulchra (Gill, 1858) and introduced O. pao as a second new species from the Orinoco basin. The holotype is specimen ANSP 181040, a male of 1.5 in standard length, collected from the Río Negrito at the bridge at La Balsa, Meta drainage, Meta department, Colombia. The valid name as recorded in Eschmeyer's Catalog of Fishes is Odontostilbe splendida Bührnheim & Malabarba, 2007.
The species is placed in the subfamily Cheirodontinae, a lineage of small characids united by a specialised, pointed dentition — the name derives from the Greek cheirodon, meaning 'hand tooth.' Odontostilbe is one of the more speciose cheirodontine genera, spanning the Orinoco and several adjacent South American river systems; it has been subject to ongoing taxonomic revision as more type material and comparative morphological data have accumulated. O. splendida is distinguished from the closely related O. pulchra and O. pao primarily by the position of the adipose fin, which in splendida begins at a vertical passing through the last two to three anal-fin rays — a character combination that separates it clearly from both congeners.
Morphology
Odontostilbe splendida is a small fish, with females reaching approximately 1.5 in standard length and males slightly smaller at around 1.5 in SL — a reversal of the pattern seen in many tetras, where females are the larger sex. The body is fusiform and laterally compressed in the manner typical of cheirodontines, with large eyes relative to head size and a terminal mouth. The semi-transparent musculature of small mid-water schoolers is characteristic of the genus.
Sexual dimorphism in mature individuals is pronounced. Males develop hooks on the rays of the anal and pelvic fins — a feature widespread among cheirodontine males — as well as slight elongation of the dorsal- and pelvic-fin rays. A gill gland, visible as a thickened, glandular patch on the gill cover, develops in reproductively active males and is believed to play a role in chemical communication during courtship. Females lack all of these features. The diagnostic adipose-fin position, set anteriorly over the rear portion of the anal fin, provides a reliable meristic character for field identification relative to the most similar sympatric congeners.
Habitat
Odontostilbe splendida is a freshwater species of the Río Orinoco basin, with the type locality situated in the Meta drainage of Meta department, Colombia. The Meta River is one of the principal Orinoco tributaries draining the eastern Colombian llanos, a vast tropical savanna landscape subject to strong seasonal flooding. Type material was collected at elevations of approximately 197 to 350 metres above sea level.
FishBase records the species as benthopelagic, with collections taken in association with muddy and sandy substrates at depths of around one metre. Published water-chemistry data from the type-locality region document a wide range of conditions: temperature 73–83 °F, pH 6.4–8.2, conductivity 30–302 µS/cm, and dissolved oxygen 1.6–7.6 mg/L. This range of values reflects the hydrological heterogeneity of the llanos, where water chemistry shifts substantially between the high-water and low-water seasons and among channel, floodplain, and pool habitats.
Feeding
No dedicated feeding study has been published for Odontostilbe splendida. Based on subfamily biology, the diet is expected to be omnivorous, centred on small aquatic invertebrates — microcrustaceans, zooplankton, and insect larvae — supplemented by algae, diatoms, and fine organic matter. Cheirodontines are typically abundant mid-water schoolers in Neotropical streams and serve as important links in the food web, consuming microinvertebrates while themselves providing forage for larger predatory fish.
In the aquarium, related Odontostilbe species accept standard small-particle prepared foods without difficulty and respond well to live and frozen microfoods such as Artemia nauplii, Daphnia, and micro-worm. Given the small body size of O. splendida, any live food offered must be appropriately fine-grained. Feeding small amounts several times daily rather than a single large ration suits the active metabolism of a fish this size.
Mating
No direct behavioural observations of mating in Odontostilbe splendida have been published. The sexual dimorphism documented at description — fin hooks, fin-ray elongation, and a gill gland in mature males — strongly suggests that males engage in active courtship display. In other cheirodontines the gill gland is associated with the release of chemical signals that influence female receptivity, and fin posturing and lateral display are the typical courtship repertoire of small male characids.
The species is assumed to follow the standard cheirodontine reproductive pattern of open-water egg-scattering with no parental investment. Males likely establish temporary social hierarchies during breeding periods, with the elongated dorsal and pelvic rays serving as visual signals to competing males and to females assessing mate quality. Spawning would be expected to occur over fine vegetation or among submerged plant debris.
Breeding
Odontostilbe splendida has not been bred in captivity in any documented account and no established husbandry protocol exists. Extrapolating from cheirodontine subfamily biology, the species is expected to be an egg-scattering open spawner that deposits small adhesive eggs among fine-leaved plants or spawning mops, with no parental care from either sex. Adults should be removed from the spawning vessel after egg deposition to prevent egg predation.
The reversal of the typical size dimorphism — females larger than males — may reflect the energetic demands of egg production in a small body, and conditioning females on high-quality live and frozen microfoods before any breeding attempt would be standard practice. Fry are likely to be very small at hatching, requiring infusoria or rotifers as first foods before graduating to Artemia nauplii. Water temperature in the mid-20s Celsius, consistent with the species' natural range, would be an appropriate starting point for any captive breeding trial.
In the aquarium
Odontostilbe splendida is not an established aquarium fish and does not appear in regular hobby trade. Its small size, Orinoco-basin origin, and limited documentation place it firmly among species known primarily from scientific collections rather than the ornamental trade.
For any serious attempt at keeping the species, conditions modelled on the Meta-drainage llanos would apply: water temperature approximately 73–82 °F, a broad pH range of 6.5–8.0 (the natural range is wide), gentle filtration producing minimal current, and soft to moderately hard water. A spacious, well-planted nano or small community tank with open water for schooling would suit the gregarious nature typical of cheirodontines. Tankmates should be similarly sized and non-predatory. Any future availability would most likely arise through specialist fishkeepers working directly with ichthyological research institutions or through targeted collection in the Meta drainage by licensed exporters.
Conservation
Odontostilbe splendida is assessed as Least Concern (LC) on the IUCN Red List, with the assessment dated December 2020. The LC designation reflects that no major range-wide threats sufficient to qualify the species for a threatened category had been identified at the time of assessment.
The Meta drainage of the Colombian llanos — the species' known type-locality region — faces ongoing pressures from agricultural expansion, cattle ranching, hydrocarbon extraction, and seasonal water management for irrigation. These activities can alter the hydrology, sedimentation regime, and water chemistry of lowland streams. As a small, benthopelagic species likely dependent on intact shallow-water habitats, O. splendida could be locally sensitive to changes in substrate quality and water clarity, even if its broader Orinoco-basin range provides some buffering. Targeted surveys to establish the full extent of its distribution and population structure within the Orinoco system would improve the basis for future assessments.