Taxonomy & naming
Phenacogaster ojitata was described by Carlos Alberto Santos de Lucena and Luiz Roberto Malabarba in 2010, in a revision of the genus Phenacogaster published in Neotropical Ichthyology. Eschmeyer's Catalog of Fishes records the valid name as Phenacogaster ojitata Lucena & Malabarba, 2010; the species has not been subjected to subsequent synonymisation and the original authority stands.
The genus Phenacogaster belongs to the family Characidae and encompasses a group of small, typically silvery South American tetras that are superficially similar across species. Genus-level revisions have repeatedly reorganised membership and relationships within the group, and the 2010 paper by Lucena and Malabarba represents the most recent comprehensive treatment. Because Phenacogaster ojitata was described within this revision, it reflects the diagnostic criteria and species concepts applied across that work.
Morphology
Members of Phenacogaster are small, elongate-to-moderately deep-bodied characids, typically reaching 1–2.5 in standard length, with a lateral line, a small adipose fin, and the general body plan characteristic of the family Characidae. Published data on the specific size of Phenacogaster ojitata are not accessible in this record; typical congeners fall within the range noted above.
The pigmentation pattern in Phenacogaster species commonly includes a dark lateral stripe or blotch on the caudal peduncle, a humeral blotch, and a generally silvery body with varying degrees of melanophore speckling. The precise diagnostic pigment characters of Phenacogaster ojitata — the traits that distinguish it from its congeners — are defined in the original description by Lucena and Malabarba (2010) and require examination of that publication for accurate detail. Data on this species are sparse in secondary sources.
Habitat
The genus Phenacogaster is broadly distributed across lowland river systems east of the Andes, including the Amazon, Orinoco, and Paraná–Paraguay basins and drainages of the Guiana Shield and Atlantic coastal rivers of Brazil. Species occur in a range of habitat types — open river channels, flooded forest margins, clear and blackwater streams — reflecting the ecological versatility of small characids.
The precise type locality and distribution of Phenacogaster ojitata are given in the original description by Lucena and Malabarba (2010); secondary literature accessible to this record does not confirm the specific drainage or country of origin. Habitat parameters such as temperature, pH, and depth for this species are not confirmed in available sources.
Feeding
Small characids in the genus Phenacogaster are generally opportunistic microinvertebrate feeders, targeting small crustaceans, insect larvae, and other zooplankton in the water column, with gut-content studies across the genus showing a broadly invertivore diet supplemented by plant particles and detritus.
No published feeding data specific to Phenacogaster ojitata are available in accessible sources. By analogy with congeners of similar size and habitat, the species likely consumes small aquatic invertebrates and microcrustaceans in the wild, and would accept fine-grade prepared foods and small live or frozen items in captivity.
Mating
No published observations of reproductive behaviour are available for Phenacogaster ojitata specifically. Characids of comparable size and morphology — including congeners in Phenacogaster — are typically open, egg-scattering spawners. Spawning in such species usually involves short, fast chases through the water column or into fine-leaved vegetation, with the pair releasing eggs and sperm simultaneously before separating; no courtship territory or lasting pair bond is established.
Adhesive or semi-adhesive eggs are scattered among submerged plant stems and roots or allowed to fall to the substrate, and both sexes ignore the eggs immediately after release. Spawning may occur across extended periods under favourable conditions rather than as a single seasonal event.
Breeding
No aquarium breeding accounts for Phenacogaster ojitata appear in the accessible literature. General breeding protocols for small Phenacogaster and closely related characids would apply as a working baseline: a separate, dim breeding tank with fine-leaved plants or spawning mops, slightly soft and warm water, and well-conditioned adults fed live or frozen invertebrates.
Egg adhesiveness varies among small characids; eggs are typically small, numerous, and at risk of predation by the parents. Removing adults after spawning or transferring the spawning medium preserves the clutch. Fry are minute at hatching and require infusoria or commercial liquid fry food before graduating to newly hatched brine shrimp nauplii. Growth in small Phenacogaster is generally rapid under good water quality.
In the aquarium
Phenacogaster ojitata is not established in the ornamental fish trade and is not available through normal hobby channels; the species is known only from scientific collections associated with its original description. Practical aquarium husbandry information does not exist in the accessible record.
As a small, schooling characid, it would in principle require the same conditions as other Phenacogaster: a well-planted aquarium, clean, well-oxygenated water, and a group of at least six to eight individuals to promote natural behaviour. Water parameters typical for lowland South American tetras — 75–82 °F, pH 6.0–7.5, low to moderate hardness — would serve as a reasonable starting point pending specific data. Any future hobbyist acquisition would most likely follow scientific collecting rather than commercial breeding.
Conservation
Phenacogaster ojitata has not been assessed by the IUCN Red List; no conservation status has been assigned. The species was described in 2010 and is known from a restricted number of scientific specimens, which is typical of newly described small characids from South American lowland drainages.
The conservation situation of the broader genus Phenacogaster varies by species and locality. Lowland Amazonian and Paraná-system drainages face ongoing pressures from deforestation, agricultural runoff, dam construction, and floodplain modification. Without a baseline population survey or range assessment for Phenacogaster ojitata, the species' susceptibility to these pressures cannot be evaluated. A formal IUCN assessment would require adequate locality data and population sampling to proceed.