Taxonomy & naming
Astyanax integer was described by the American ichthyologist George S. Myers in 1930. The type specimen is held at the California Academy of Sciences (CAS Ichthyology collection), and the valid name is confirmed by Eschmeyer's Catalog of Fishes as Astyanax integer Myers, 1930. Because the species was described within Astyanax, where it remains, no parenthetical authority is used.
A 2018 revision of the Astyanax orthodus species-group by Ruiz-C and colleagues, published in the European Journal of Taxonomy, examined specimens including A. integer and refined its distributional and morphological limits. The orthodus group is a cluster of closely related Orinoco-basin Astyanax sharing overlapping meristic characters; the revision drew on museum series from Colombia and Venezuela to clarify species boundaries. A. integer belongs to the enormous family Characidae and the hyperdiverse genus Astyanax, which ranges across much of Central and South America and represents one of the most species-rich characid lineages on the continent.
Morphology
Specimens examined in the Ruiz-C et al. (2018) revision measured 2–4.5 in standard length, making A. integer a small to medium-sized Astyanax. The species is benthopelagic in habit and built accordingly: a moderately compressed, oval-bodied fish with the typical characid profile — large eyes, a terminal mouth, and a well-forked tail.
Like most members of the genus, A. integer is predominantly silver with a lateral stripe or body markings that may vary with specimen age and preservation state. The adipose fin, characteristic of characids, is present. FishBase records a trophic level of 2.9, consistent with omnivorous feeding on small invertebrates and plant material. Detailed meristic counts and colour-pattern descriptions for live specimens are sparse in the available literature; published accounts focus primarily on preserved museum material from the revision.
Habitat
Astyanax integer is distributed across the upper Meta River drainage in Colombia — with records from Tauramena and Tauramena Casanare, the Urichare Creek near Granada (Meta department), and the Cravo Sur River near Yopal — and extends into Venezuelan Orinoco tributaries, including a creek near Guatiré and streams draining to the Apure, among them Rabipelado Creek.
The Meta basin spans a steep habitat gradient from Andean piedmont streams to open-water llanos channels and gallery-forest rivers. Astyanax are among the most widespread and adaptable characids in South American freshwaters, and A. integer is associated with the benthopelagic zone of these warm, lowland to sub-Andean waters. The IUCN notes a stable population trend with no evidence of major decline across this range, which spans two countries in the western Orinoco system.
Feeding
Astyanax integer is an omnivore with a trophic level of approximately 2.9, placing it at the lower end of the food chain and consistent with a diet of small invertebrates, insect larvae, plant material, detritus, and algae. This generalist feeding strategy is characteristic of the genus and contributes to its wide ecological success across diverse Neotropical freshwater habitats.
In the aquarium, members of the Astyanax genus are undemanding feeders that readily accept high-quality flake and pellet foods, supplemented with frozen or live items such as Daphnia, brine shrimp, and bloodworm. Vegetable-based foods round out a balanced diet. Varied feeding improves condition and colour in most small characids.
Mating
Astyanax integer, in common with its close relatives, is presumed to be an egg-scattering open spawner with no parental care — the standard reproductive mode across the genus. Males likely engage in brief pursuit and courtship of females, with spawning stimulated by environmental cues such as temperature change or rainfall, mimicking the seasonal flooding cycles of the llanos.
Broadly across Astyanax, males and females school together outside breeding condition, and courtship is vigorous and communal rather than pair-bonded. Specific courtship behaviour for A. integer has not been documented in the available literature; observations from related Meta-basin congeners suggest energetic chasing and rapid, scattered egg release over vegetation or open substrate.
Breeding
No dedicated captive-breeding accounts for Astyanax integer appear in the reviewed literature. Based on the biology of closely related Astyanax, breeding in captivity would follow the egg-scattering pattern typical of the genus: conditioned adults spawn over fine-leaved plants or a bare substrate, releasing small adhesive or semi-buoyant eggs that the adults will readily consume if left in the breeding tank.
Best practice for genus-typical Astyanax breeding involves conditioning adults on live and frozen foods, then placing them in a separate spawning tank with spawning mops or Java moss, removing the parents after spawning is complete. Eggs generally hatch within 24 to 48 hours at tropical temperatures, and the tiny fry require infusoria or commercial liquid fry food initially before graduating to newly hatched brine shrimp. Specific data on clutch size and incubation time for A. integer await documentation.
In the aquarium
Astyanax integer is not a commonly traded species in the ornamental fish hobby, and most aquarists are unlikely to encounter it by name. However, as a medium-sized, schooling Orinoco-basin characid it should suit a standard community aquarium designed for South American riverine species: a well-filtered tank of at least 31.5 in in length, water temperatures in the mid-to-upper 20s Celsius, and near-neutral to slightly acidic pH consistent with the soft to moderately hard waters of the Meta drainage.
If kept, a school of six or more would allow natural schooling behaviour and reduce stress. Tankmates should be similarly sized and peaceful — other small to medium Neotropical characids, peaceful dwarf cichlids, and corydoras catfish would all be compatible. A planted tank with some open swimming space and dim to moderate lighting mimics the gallery-forest streams of its home range.
Data on the availability of this species in the trade are sparse; most aquarists interested in Orinoco tetras will encounter the genus through more widely kept congeners.
Conservation
Astyanax integer is assessed as Least Concern (LC) on the IUCN Red List, with a stable population trend. Its range across the Meta River basin in Colombia and Venezuela, and into Apure-system tributaries, is broad enough relative to the pressures currently documented against it that no range-wide decline threshold has been met.
The Meta basin does face ongoing pressures from agricultural expansion, cattle ranching on the llanos, and hydropower development, all of which can affect freshwater fish communities through habitat alteration, sedimentation, and flow modification. These are landscape-scale threats that affect many co-occurring species rather than A. integer specifically. No targeted conservation measures are documented for this species, and its common-name obscurity means it draws little dedicated hobbyist or research attention. The stable IUCN assessment reflects the current best evidence, but baseline population data for this and many congeners in the Orinoco system remain limited.