Taxonomy & naming
Odontostilbe ecuadorensis was described by Luiz Malabarba and Carla Bührnheim in 2006 as part of their ongoing revision of the genus Odontostilbe, a project that substantially expanded and redefined the genus within the tribe Cheirodontini of the subfamily Stevardiinae (Characidae). The species is recorded in Eschmeyer's Catalog of Fishes under the authority Bührnheim & Malabarba, 2006. The type locality lies in Ecuador; the species has also been confirmed from adjacent Peru, placing its range within the western Amazon basin.
Odontostilbe belongs to the family Characidae as currently recognised and sits within a clade of small, schooling cheirodontine tetras that includes Serrapinnus and Compsura among others. The genus name combines the Greek odous (tooth) with stilbe (glitter or sheen), an allusion to the small but well-developed dentition characteristic of the group. At the species level, ecuadorensis is a straightforward geographical latinism meaning 'of Ecuador', reflecting the country in which the type series was collected.
Morphology
Odontostilbe ecuadorensis is a small tetra, typical of its genus in reaching only a few centimetres in standard length. The body is slender and fusiform — elongated and only moderately compressed laterally — with a relatively pointed snout, large eyes, and the forked tail characteristic of active schooling fish. The dorsal profile is gently arched, the ventral profile roughly parallel to it, giving the fish a neat, streamlined outline.
Coloration is modest: a silvery body with a faint lateral stripe or midlateral pigment band running from behind the opercle toward the caudal peduncle, typical of the genus. There is no bold pattern, no red or blue pigment, and no extended fin rays in either sex. The fins are transparent to faintly yellowish. Like other cheirodontines, it possesses small but distinct teeth with multiple cusps, which distinguish Odontostilbe from superficially similar genera. Sexual dimorphism, where documented in the genus, is subtle — females tend to be deeper-bodied when gravid, but differences are not pronounced outside of breeding condition.
Habitat
The species is recorded from Ecuador and Peru, placing it within the western Amazon basin. Small tetras of the genus Odontostilbe are typically inhabitants of lowland to submontane streams, minor tributaries, and flooded marginal habitats associated with the Amazon and its tributaries. They tend to occupy clear to slightly turbid, warm waters with moderate current, and are most often encountered in the mid-water column of smaller streams and tributaries where they form loose to dense schools.
Water conditions across the western Amazon lowlands where this species occurs are typically warm (around 73–82 °F), soft to moderately soft, and acidic to near-neutral (pH 5.5–7.0), reflecting the predominantly sandy and organic substrates of the region. Specific microhabitat data for O. ecuadorensis are sparse in the available literature; the habitat profile given here is inferred from the distribution and from published data for congeners and co-distributed small characids.
Feeding
Odontostilbe ecuadorensis is presumed to be a micropredator or omnivore, consistent with the feeding ecology documented for other members of the genus and the tribe Cheirodontini more broadly. Cheirodontine tetras typically feed on small invertebrates — microcrustaceans, insect larvae, and zooplankton — taken in the water column, supplemented with fine organic particulates, algae, and occasionally small insects at the surface.
In the aquarium, species of Odontostilbe readily accept fine-grade prepared foods including small flake and micro-pellets, and respond well to frozen and live foods such as Artemia nauplii, Daphnia, micro-worms, and Cyclops. Because of their small adult size, particle size matters: foods should be appropriately small so that all individuals feed efficiently. A varied diet helps maintain condition and, in a breeding group, improves reproductive readiness.
Mating
Odontostilbe ecuadorensis, like other members of the genus, is an egg-scattering open spawner. Males and females form loosely coordinated pairs or briefly associate during spawning, with no prolonged courtship ritual documented in the available literature. Spawning takes place among fine-leaved aquatic vegetation or over other submerged structure, where adhesive or semi-adhesive eggs are deposited and immediately abandoned by both parents.
No parental care of any kind is provided; the adults do not guard, fan, or attend the eggs after spawning, and will readily consume both eggs and any fry they encounter. In congeners and related cheirodontines, spawning activity is often triggered by a small temperature increase, a water change simulating rain-season conditions, or a shift to a slightly lower pH. Males in breeding condition may show faint intensification of coloration or increased chasing behaviour toward females.
Breeding
Captive breeding of Odontostilbe ecuadorensis has not been widely reported in the hobbyist literature, and detailed accounts are sparse. Based on the biology of the genus and closely related cheirodontine tetras, the species is expected to breed in a manner typical of small egg-scattering characids: a conditioned pair or small group is placed in a well-planted breeding tank with fine-leaved plants or a spawning mop, soft acidic water, and subdued lighting; spawning occurs near the substrate or among the vegetation, with small numbers of eggs deposited over the course of a spawning session.
Eggs should be removed or the adults transferred after spawning to prevent predation. At warm incubation temperatures (around 79–82 °F) hatching can be expected within 24–48 hours, and free-swimming fry appear a few days later. First foods for the very small fry need to be appropriately fine — infusoria, rotifers, or commercial liquid fry foods — before progressing to newly hatched brine shrimp nauplii. These inferences are based on congener biology; breeders working with this species should treat the details as a starting framework rather than confirmed data.
In the aquarium
Odontostilbe ecuadorensis is rarely encountered in the mainstream aquarium trade and is primarily of interest to specialists in small South American characids and to aquarists who seek out less common species from the western Amazon. When available, it is best kept as a school of eight or more individuals; like all cheirodontines it is a social fish that behaves poorly in isolation or very small groups, becoming timid and prone to stress-related problems.
A small to medium aquarium (23.5–31.5 in or longer) with a soft substrate, moderate planting, gentle filtration, and good water quality suits the species well. Water should be soft, slightly acidic, and warm (around 75–81 °F), matching the conditions of its native western Amazon streams. Tankmates should be similarly sized and peaceful; it is easily outcompeted by boisterous or larger fish. Avoid species that nip fins or that are large enough to view the tetras as prey. Given its small size and retiring nature, a species or community tank with other small Amazonian fishes — pencilfish, small corydoras, dwarf cichlids — shows it at its best.
Conservation
Odontostilbe ecuadorensis has not been assessed by the IUCN Red List; its status is Not Evaluated (NE). The western Amazon basin of Ecuador and Peru, where the species occurs, includes areas under varying degrees of pressure from deforestation, agricultural runoff, and artisanal gold mining, all of which degrade small stream habitats. However, in the absence of a formal assessment, the actual population status and degree of threat to this species are unknown.
The species' occurrence in both Ecuador and Peru suggests it is not restricted to a single locality, which is generally a positive indicator for resilience. As with many small, nondescript characids from species-rich lowland Amazonian systems, the greatest risk may be the pace of habitat change outstripping taxonomic knowledge — species can decline before they are well enough known for anyone to notice. An IUCN assessment and basic survey work on its distribution and abundance would provide the baseline needed to evaluate whether any conservation action is warranted.