Taxonomy & naming
Henrique R. Varella and Ricardo Britzke described Apistogramma eleutheria in 2016, in Ichthyological Exploration of Freshwaters (27(1): 81–95) — a paper that named a second new dwarf cichlid, Apistogramma flavipedunculata, from the same upland river system. The holotype, MZUSP 115293, is a 1.5 in SL brooding male held at the Museu de Zoologia da Universidade de São Paulo, collected in the upper rio Treze de Maio, a tributary of the middle rio Curuá on the Serra do Cachimbo, Pará, Brazil. The act is registered in ZooBank (65196ACB-8A1C-4D68-A82E-DE116F9214AD), and Eschmeyer's Catalog of Fishes, FishBase, GBIF and the Cichlid Room Companion all treat the species as valid with no synonyms.
Specialists knew the fish before it had a name. It was collected during the All Catfish Species Inventory's PIPE Expedition to the Serra do Cachimbo in October 2007 — the same campaign that produced the celebrated 'titan among dwarfs,' Apistogramma kullanderi — and it first appeared in print as the placeholder 'Apistogramma sp. Treze de Maio' in Varella and Sabaj Pérez's 2014 description of that larger species. Varella and Britzke placed Apistogramma eleutheria in the broad Apistogramma regani species group but found its most telling resemblance to be with Apistogramma kullanderi: brooding females of both develop a very dark, blackish patch over the median gular (throat) region. In Apistogramma eleutheria the pigment stays on the throat and the lower edge of the opercular series and branchiostegal membranes, whereas in Apistogramma kullanderi it spreads much further, across the underside of the head and back onto the belly and along the anal-fin base. The species also shares with Apistogramma kullanderi and a few other regani-group fishes an unusual count of four anal-fin spines, where most Apistogramma have three.
The specialist author Mike Wise, writing on apistogramma.com, sets the fish closest to Apistogramma kullanderi and to the undescribed 'Apistogramma sp. Peixoto' of the upper Tapajós, within an Apistogramma kullanderi-complex of the regani group — a lineage he considers among the most plesiomorphic, or ancestral-looking, in the whole genus. He notes that Apistogramma eleutheria is smaller and far less colourful than Apistogramma kullanderi, closer in that respect to 'Apistogramma sp. Peixoto.' How a small-bodied fish sits inside a complex otherwise made up of large, robust species is an open question, and no molecular phylogeny has yet resolved it in print.
Morphology
This is a small Apistogramma even among a genus of dwarfs. The type series tops out at about 1.5 in (1.5 in) standard length — the maximum FishBase carries — and the holotype male measured 1.5 in SL. Build and proportions follow the regani-group template, a moderately elongate, laterally compressed body with a continuous dorsal fin of even spines, but the species is defined less by shape than by its dark pigment, the trait behind the FishBase descriptor 'Dark dwarf cichlid' (a database label, not a hobby name).
The diagnostic feature is the coloration of brooding females. Ripe females develop a very dark, blackish patch on the median area of the gular (throat) region, along the ventral edge of the opercular bones and across the branchiostegal membranes beneath the head. Only Apistogramma kullanderi shares this dark-throat livery, in a more sweeping form; in every other regani-group congener the throat lacks such heavy black. As in most dwarf cichlids the sexes differ — males grow somewhat larger and develop more produced fins than females — but the published description emphasizes the brooding-female pattern rather than a detailed account of male nuptial colour, and reliable in-life photographs of wild fish remain scarce. No morphometric or meristic data have been published beyond the type series, so any claim about the full size range, fin counts or male breeding dress should be treated as provisional.
Habitat
On current knowledge Apistogramma eleutheria is a narrow endemic of the upper rio Treze de Maio, a tributary of the middle rio Curuá on the Serra do Cachimbo — an isolated plateau of the Brazilian (Guaporé) Shield rising to roughly 1640 ft above sea level in southern Pará, Brazil. The Curuá drains north off the plateau into the rio Iriri, a major tributary of the lower rio Xingu, which places this fish in the clearwater Xingu basin of the Amazon rather than in the Madeira system. The Treze de Maio's headwaters rise on the same highland and, like the upper Curuá, are cut off from their lower courses by large waterfalls; Apistogramma eleutheria lives above one such fall and is, the describers note, isolated from the lower river by it.
No water chemistry or temperature has been published for this population, so the picture is drawn by analogy with the immediately adjacent, intensively sampled habitat of Apistogramma kullanderi on the same plateau. There, tributaries of the upper Curuá were described as 'clear to mild blackwaters,' and the cichlids were taken from shallow, sluggish backwaters shaded by overhanging bank vegetation. Upland Shield Apistogramma generally live in soft, acidic, warm water, and that is the reasonable expectation here — but it is inference, not measurement, and is flagged as such. The waterfall isolation is the heart of this fauna's interest: above the falls the dwarf cichlids sit beyond the reach of most large predatory fishes, and the plateau's streams hold a clutch of small-range endemics, several of them characins found nowhere else.
Feeding
No diet study exists for Apistogramma eleutheria, and FishBase carries only a modelled trophic level of about 3.3, inferred from the size and ecology of close relatives rather than from gut contents. What can responsibly be said is generic to the genus: Apistogramma are micropredators of the leaf litter and shallow margins, sifting fine substrate and picking through detritus, biofilm and submerged litter for small invertebrates — chironomid and other insect larvae, microcrustaceans and aquatic worms — taken at and just above the bottom. In the clear-to-blackwater, vegetation-shaded backwaters its neighbours occupy on the Serra do Cachimbo, a small benthic invertivore of this kind would forage over leaf litter and root tangle in the slack water along the banks. That role is plausible and consistent with everything known of the genus, but for this particular species it is an expectation, not a documented fact.
Mating
The mating behaviour of Apistogramma eleutheria has not been described — there are no published spawning observations, in the aquarium or the wild. The original description does record a strong clue to its reproductive style: the holotype is an adult male in brooding condition, and the species' single diagnostic trait is the dark gular livery of brooding females, which implies females in maternal nuptial dress exactly as expected of the genus. Across Apistogramma the near-universal pattern is a polygynous, harem-forming cave spawner, in which a male holds a loose territory overlapping the smaller home ranges of several females, each defending her own spawning cavity. By close analogy with its relatives, Apistogramma eleutheria is almost certainly a female-tending cave spawner with a similar social structure — the female taking charge of the nest and brood while the male patrols the wider territory. Stated plainly, that is inference from the genus and from the brooding-condition type specimens, not a behavioural account of this species, which remains unstudied.
Breeding
Nothing has been published on the breeding of Apistogramma eleutheria — no clutch size, no egg or fry development, no account of parental care specific to it. As far as the literature shows the species has never been bred in aquaria and is essentially unknown in the hobby, having reached print straight from a remote scientific expedition rather than through the ornamental trade.
What can be said is bounded by the genus and by the type material. Apistogramma are overwhelmingly female-tended cave (or cavity) spawners: the female deposits a modest clutch of adhesive eggs on the underside of a cave roof, root or leaf, guards and fans them, leads the wrigglers and then the free-swimming fry, and shifts into a high-contrast maternal coloration during the brood — the very dark-throated 'brooding female' livery on which Apistogramma eleutheria was diagnosed. That diagnosis is itself the strongest direct evidence of its breeding mode, since females in brooding colour and a male in brooding condition were collected together. Fecundity is unrecorded: small Apistogramma typically lay modest clutches on the order of forty to eighty adhesive eggs, but that is a genus-wide figure offered by analogy, not a count from this fish. Everything beyond the brooding-condition types — true fecundity, timing, spawning triggers, the duration of care — is undocumented for this species and should not be stated as if it were.
In the aquarium
Apistogramma eleutheria is, as of writing, essentially unknown in the aquarium hobby: described from a remote expedition, it has no documented trade history and no published keeper account. Everything below is extrapolated from the genus, from close relatives such as Apistogramma kullanderi, and from the soft, acidic, clear-to-mild-blackwater chemistry of its native Serra do Cachimbo headwaters. Anyone keeping it would be working at the frontier of what is known, and should treat genus-typical Apistogramma husbandry as the default while watching for signs that a pinpoint endemic proves more demanding.
Tank: with an adult male around 1.5 in standard length, a 15–20 US gal aquarium (a 23.5–27.5 in footprint) is the sensible minimum for a pair or small harem, and more floor area is always better. Furnish it dim, with deep fine sand, a covering layer of dried leaf litter, driftwood roots, and several small caves or half-coconut shells as spawning sites.
Water: this is the non-negotiable. The facts file carries pH 5.0–6.5 and 75–82 °F as basin-typical estimates; provide soft, acidic water in that band, kept very clean and stable. Hard or alkaline tap water will not serve, and the fish should not go into a tank whose chemistry has not been verified.
Tankmates: keep it as a single-species tank, or with small, peaceful midwater dithers from soft-water Amazonian systems — neon or cardinal tetras, ember tetras, pencilfish. Avoid anything large enough to eat it, other substrate-contesting small cichlids, and bottom-roaming loaches or corydoras that disturb cave sites; small Caridina shrimp should be expected to be eaten or displaced.
Social: expect a polygynous structure — one male over the ranges of two or three cave-holding females — which spreads his aggression and usually settles better than a forced pair, though a lone female may turn on the male once she has eggs. Sexing is easy in adults: males are larger, with more elongate fins, and lack the dark gular patch that erupts on brooding females.
Common mistakes: the usual error with soft-water dwarfs is assuming an acidic tank tolerates higher nitrate. It does not — these oligotrophic-stream fish need near-pristine water, and even modest nitrate accumulation will suppress breeding and invite lateral-line disease, so change water regularly with matched-chemistry water. Anyone who obtains the fish through specialist breeders or scientific fish-room networks would do the hobby a real service by documenting the experience and publishing it through the specialist Apistogramma community.
Conservation
Apistogramma eleutheria has not been evaluated by the IUCN Red List; its status is formally Not Evaluated. FishBase (Red List version 2025-2) records it as Not Evaluated, the Cichlid Room Companion states explicitly that it has not been assessed, and GBIF's backbone record (taxon key 9840274) carries no threat status — there is, in short, no IUCN species page for it to resolve to. It has no CITES listing and is not known in the aquarium trade.
The absence of an assessment is not the absence of risk, and here the risk is structural. Apistogramma eleutheria appears to be a single-river endemic of one stream above one waterfall on the Serra do Cachimbo — the kind of pinpoint range that leaves a species acutely exposed to any local disturbance. The threat is not hypothetical: the companion paper on Apistogramma kullanderi maps the small hydropower works already built on this fauna's streams, including a 33 ft falls on the upper Curuá converted to a weir and reservoir for the PCH Salto Buriti plant, with water temporarily re-routed during construction. Dams, impoundment, the clearing of the shading bank vegetation these fish shelter under, and the steady advance of mining and agriculture across southern Pará all bear on a narrow-range highland endemic with nowhere else to go. The honest summary is that Apistogramma eleutheria is too poorly known to assign a Red List category, yet its tiny documented range and the visible infrastructure pressure on its watershed are exactly the conditions under which a microendemic can decline unnoticed. A formal assessment, and basic survey work to learn whether it occurs anywhere beyond the Treze de Maio, are overdue.