Taxonomy & naming
Odontostilbe dierythrura was described by Henry Weed Fowler in 1940 from material collected in the Amazon drainage of Bolivia. The valid name stands as Odontostilbe dierythrura Fowler, 1940 in Eschmeyer's Catalog of Fishes, the governing authority for characid nomenclature. Fowler was a prolific Philadelphia ichthyologist who described hundreds of South American species during the mid-twentieth century, though his descriptions were sometimes based on limited material.
The genus Odontostilbe belongs to the subfamily Stevardiinae (tribe Stevardiini) within the family Characidae. It comprises a group of small, slender characids distributed across northern and central South America, and several species formerly placed in Odontostilbe have been reassigned following molecular phylogenetic work. The specific epithet dierythrura is Greek in origin, from di- (two) and erythros (red) plus oura (tail), most likely referring to a reddish coloration on or near the caudal fin that presumably distinguished the type material.
Morphology
Odontostilbe dierythrura is a very small characid, with FishBase recording a maximum standard length of 1 in. Like other members of the genus it is slender and laterally compressed, with the streamlined, fusiform body plan typical of small schooling tetras. The head is small and the mouth terminal.
Specific details of fin-ray counts, scale counts, and coloration pattern in life are not well documented in the accessible literature. The specific name dierythrura suggests that reddish pigmentation on or adjacent to the caudal fin was a noted feature of the type specimens; this is consistent with the pattern seen in other small Odontostilbe species, many of which show orange or red tints in the caudal and other fins. As with most members of the genus, sexual dimorphism is likely subtle, with females fuller-bodied when ripe.
Habitat
FishBase records Odontostilbe dierythrura as a freshwater benthopelagic species occurring in tropical South America within the Amazon drainage of Bolivia. Its habitat is the lowland stream and river systems of the Bolivian Amazon basin, which encompass clear- and white-water tributaries flowing through forest and savanna landscapes at low to moderate elevations.
Small Odontostilbe species typically inhabit the middle and upper water column of slower-moving reaches, backwaters, and flooded margins, often in association with aquatic vegetation or submerged roots where they school in the open but have ready cover. Water conditions in Bolivian Amazon tributaries are generally soft and slightly acidic to neutral, with low conductivity, warm temperatures, and seasonal fluctuation tied to the wet-dry cycle. Specific collection data for this species beyond the country-level record are not available in the accessible literature.
Feeding
Odontostilbe dierythrura, like other members of the genus, is presumed to be a micro-predator and opportunistic omnivore in the wild, feeding on small invertebrates, zooplankton, insect larvae, and organic particles in the water column. At 1 in standard length it is among the smallest characids in the Amazon basin, and its diet would be scaled accordingly — fine particulate matter, tiny crustaceans such as copepods and Daphnia, microalgae, and the smallest instars of aquatic insects.
In captivity, species of this size class accept fine-grade prepared foods including micro-pellets and crushed flake, supplemented with small live or frozen foods such as newly hatched brine shrimp, micro-worms, and Cyclops. A diet rich in small live and frozen items helps maintain condition and colour. Feeding multiple small portions daily suits the metabolism and mouth size of a 1 in fish.
Mating
Spawning behaviour in Odontostilbe dierythrura has not been specifically documented in the literature, but the genus follows the standard characid reproductive strategy: egg-scattering with no parental care. Males in breeding condition likely display to females with fin-flaring and parallel swimming, directing females toward fine-leaved vegetation or areas of fibrous substrate where eggs are scattered.
In related small Odontostilbe species, spawning is diffuse and may occur repeatedly in small batches rather than a single massed event. Adhesive or semi-adhesive eggs are deposited among fine-leaved plants or root mats and receive no further attention from the parents. At 1 in, mature fish are reproductively active when small, and in good conditions spawning may be nearly continuous rather than seasonal.
Breeding
No captive breeding records specific to Odontostilbe dierythrura are documented in the accessible hobby literature, and the species is essentially unknown in the ornamental trade. By analogy with other small Odontostilbe and with small characids generally, breeding would involve egg-scattering among fine-leaved plants or a synthetic spawning mop, with the adults removed immediately after spawning to prevent egg predation.
Eggs of small characids at this size class are tiny and adhesive, typically hatching within 24–48 hours at tropical temperatures. The larvae would require the finest available first foods — infusoria, rotifers, or commercial liquid fry food — for the first several days before accepting newly hatched brine shrimp nauplii. Water quality during rearing must be excellent, as small fry are sensitive to dissolved waste. Specific data on clutch size, incubation time, and fry development for this species are absent from the available literature.
In the aquarium
Odontostilbe dierythrura is essentially unknown in the ornamental fish trade and would be an extreme rarity in any collection. Should it become available — most likely as a byproduct of wild-collected Bolivian community fish — it would require a nano or species-specific aquarium given its 1 in maximum size, where it would be vulnerable to being outcompeted or preyed upon by anything more than a similarly small tankmate.
As with other micro-characids, a densely planted aquarium with a dark substrate and gentle filtration, soft and slightly acidic water, and small schooling companions of comparable size would be appropriate. Bolivian Amazon community fish — small pencilfish, other miniature characids, and dwarf corydoras — make natural and scale-appropriate companions. Water temperature in the mid-to-upper 20s Celsius, pH near neutral to mildly acidic, and fine-grade foods offered several times daily would form the basis of care. The species' obscurity means practical husbandry data remain limited.
Conservation
Odontostilbe dierythrura has not been assessed by the IUCN Red List as of this writing. It is known from the Amazon drainage of Bolivia, a region that encompasses extensive lowland forest systems that remain broadly intact but face growing pressure from agricultural expansion, deforestation, and associated changes to water quality and hydrology in the Bolivian Amazon lowlands.
As a very small, range-restricted species with limited documentation, it falls into a category of South American freshwater fish that receive little conservation attention because they are poorly known and not commercially significant. Catalog of Fishes recognises the species as valid, but biological data beyond the basic distributional record are sparse. Any future assessment would depend on updated field surveys to establish current range, population status, and habitat condition.