Taxonomy & naming
Odontostilbe dialeptura was described by William L. Fink and Stanley H. Weitzman in 1974 in their monographic revision of the genus Odontostilbe. The species is currently placed in the tribe Stevardiinae of the family Characidae, though Odontostilbe has at times been assigned to Cheirodontinae; the exact tribal boundaries in this part of the family tree have been reworked repeatedly and the placement should be understood as current rather than settled. Eschmeyer's Catalog of Fishes lists the valid name as Odontostilbe dialeptura (Fink & Weitzman, 1974), with the parenthetical authority indicating that the species was originally described in a combination that differs from its current genus assignment.
The genus Odontostilbe — from the Greek for 'toothed' and 'shining' — is a diverse New World characid group ranging from Central America south through much of tropical South America. O. dialeptura sits near the northern edge of that range, with a distribution largely restricted to the Pacific versant of Panama and Costa Rica. The type locality lies within the coastal plain drainages of Coclé Province, Panama.
Morphology
O. dialeptura is a small, elongate, and laterally compressed characid with a vertebral count of 32–34, typical for the genus. Maximum recorded standard length is 1.5 in. The body is pale brown with a bronzy-green shading on the dorsal and lateral surfaces, and the scales along the back carry dark margins that produce a faint reticulated pattern visible under good lighting.
The lateral line is complete or nearly so, and the overall build is slender enough to distinguish the species from deeper-bodied small characids sharing the same streams. The jaws bear the comb-like teeth characteristic of Odontostilbe — small, multicuspid, and arranged in a single outer row — from which the genus takes its name. There is no distinctive humeral spot or caudal spot, and the species relies more on overall proportions and meristics for identification than on obvious pigment marks.
Habitat
The species is distributed across Pacific-versant drainages from Coclé Province in central Panama northward to Puntarenas Province in Costa Rica, at elevations of roughly 66–295 ft above sea level. It favours lowland environments: stagnant roadside puddles, agricultural drainage ditches, slow-flowing creek channels, and similar warm-water habitats at the coastal plain margin. These are markedly different from the clear, fast hill streams preferred by many co-occurring small characids.
Water conditions are warm, with temperatures of 72–95 °F recorded across the species' range — a range that reflects both naturally warm lowland conditions and the additional heating typical of shallow, exposed, sun-struck ditches. The preference for marginal, disturbed-looking microhabitats has likely helped the species persist in an intensively farmed landscape, though it also makes those populations sensitive to drainage schemes and pesticide runoff that can eliminate standing-water habitats entirely.
Feeding
FishBase records O. dialeptura as herbivorous, with the diet consisting primarily of aufwuchs, diatoms, filamentous algae, and small seeds. This aligns with the broader cheirodontine feeding guild, where grazing on fine attached algae and organic detritus is common among small, shallow-water species.
In captivity the species can be expected to accept most fine-grained foods including good-quality flake, micro-pellets, and frozen or live small invertebrates. Including algae-based foods in the diet, such as spirulina-enriched flake or blanched vegetables, will better replicate the natural herbivorous tendency and support long-term health.
Mating
No detailed field or laboratory observations of mating behaviour have been published specifically for O. dialeptura. Based on the reproductive biology documented for related Odontostilbe and Cheirodontinae species, it can be reasonably inferred that the species is a free-spawning egg-scatterer with no parental care. Males likely chase and pursue females among fine-leaved aquatic vegetation, with spawning occurring in brief bursts.
The genus Odontostilbe shows no documented secondary sexual dimorphism analogous to the glandular caudal organ seen in some stevardiines, and spawning is not thought to involve internal fertilisation. Ripe females may be visibly fuller-bodied than males when in breeding condition.
Breeding
Specific breeding accounts for O. dialeptura in captivity are absent from the available literature. By analogy with closely related small cheirodontine characids, breeding is likely to follow the standard open-spawning pattern: adhesive eggs scattered among fine-leaved aquatic plants or over a soft substrate, with adults offering no parental care and readily consuming their own eggs if given the opportunity.
A spawning setup with clumps of Java moss or synthetic spawning mops, warm water at the upper end of the temperature range, and slightly reduced lighting would offer conditions suitable for a first breeding attempt. Eggs should be separated from adults immediately after spawning. Fry will likely require very small first foods — infusoria or commercial liquid fry food — given the tiny adult size, graduating to newly hatched brine shrimp nauplii as they grow.
In the aquarium
O. dialeptura is rarely encountered in the hobby and is not commercially traded to any significant degree. Its small size — under 1.5 in — and tolerance of warm temperatures make it technically straightforward to maintain in a well-filtered nano or small species tank. The preferred temperature range of 72–95 °F means even an unheated tropical room aquarium may suffice in warmer climates.
A species-only setup or a tank with other small, non-predatory fish of similar size would be appropriate. Dense planting with fine-leaved plants such as hornwort or java moss would replicate the vegetation-rich shallow habitats the species uses in the wild and provide visual security. As with most small characids, a group of at least six individuals is advisable to prevent stress and to observe natural social behaviour. Water quality must be kept high despite the species' tolerance of warm, marginal habitats — clean water with adequate filtration remains non-negotiable.
Conservation
O. dialeptura is assessed as Near Threatened (NT) on the IUCN Red List (assessment date 11 April 2019, criteria B1ab(iii)). The listing recognises that the species occupies a restricted range on the Pacific coastal plain of lower Central America, where agricultural expansion — particularly intensive banana and pineapple cultivation — has dramatically altered the lowland drainage network through channelisation, irrigation withdrawal, and pesticide contamination. The very microhabitats the species favours, shallow roadside ditches and small temporary pools, are among the most vulnerable to drainage improvement schemes.
The NT status reflects genuine concern about ongoing habitat loss rather than a current population crash, with no evidence that the species has undergone the severe declines that would justify a threatened listing. Continued monitoring of Pacific-slope lowland fish communities in Panama and Costa Rica would be needed to detect any deterioration in status. No captive conservation programme is known to exist for this species.