Taxonomy & naming
The species was described by the Brazilian naturalist Alípio de Miranda Ribeiro in 1918 as Nannacara hoehnei, in the Cichlidae fascicle of the published reports of the Commissão de Linhas Telegraphicas Estrategicas de Matto-Grosso ao Amazonas — the great telegraph-line survey across the Brazilian interior led by Cândido Rondon. The type material came from the Rio Branco, a tributary of the Araguaia River in what was then Mato Grosso; the holotype is held in the Museu Nacional, Rio de Janeiro (MNRJ 1245), with two paratypes (MNRJ 1255). Miranda Ribeiro himself revisited the type series in his 1955 type catalogue.
The original placement in Nannacara — a genus of Guiana-shield dwarf cichlids — never sat comfortably. Over the following decades the species was shuffled through several genera: Fowler (1954) listed it as Aequidens hoehnei, and Kullander, in the 2003 'Checklist of the Freshwater Fishes of South and Central America', also treated it as a species of Aequidens (with the broad, polyphyletic 'Cichlasoma' likewise invoked for many such orphaned acaras). None of these assignments rested on a phylogenetic analysis; the fish simply did not match the diagnostic features of any well-defined genus.
The matter was settled by Felipe P. Ottoni and José Leonardo O. Mattos in 2015 (Vertebrate Zoology 65: 65–79), who re-described the species, ran a morphological phylogenetic analysis, and found it did not belong to any existing genus of the tribe Cichlasomatini. They erected the new monotypic genus Rondonacara to hold it, recovering it as the sister taxon of Laetacara. The genus is diagnosed by a striking unique feature — transversal streaks rising from the bases of the dorsal-fin spines and rays in live fish — together with a suite of characters: a horizontally oriented flank stripe ending toward the caudal-fin base, a conspicuous suborbital bar, a non-ocellated caudal spot on the mid-fin, a scaleless preopercle, two supraneurals, and uniserial predorsal squamation. The current valid combination, confirmed by Eschmeyer's Catalog of Fishes, is Rondonacara hoehnei (Miranda Ribeiro 1918), in the subfamily Cichlinae, tribe Cichlasomatini.
Morphology
Rondonacara hoehnei is a small cichlid. FishBase gives a maximum of 3 in standard length, while Kullander (2003) cited a largest known specimen of about 2 in total length; the fish is, in practice, a dwarf by cichlid standards and unlikely to exceed roughly 3 in even at its largest. The body is fusiform and moderately deep, the typical 'acara' build of the Cichlasomatini. Fin counts run to 13–14 dorsal spines and 9–11 dorsal soft rays, with 3 anal spines and 9–10 anal soft rays.
The diagnostic colour pattern is the genus's defining trait. In live fish, a series of transversal (vertical) streaks runs down from the insertion points of the dorsal-fin spines and rays onto the upper body — a feature found in no other member of the tribe; in preserved specimens only the proximal stubs of these streaks survive. A dark longitudinal stripe runs horizontally along the flank, directed toward the base of the tail, and a conspicuous suborbital (cheek) bar crosses the face below the eye. There is a single dark caudal-peduncle spot set on the midline of the fin base, and — unlike in many relatives — it is not ringed by a pale ocellus. At the skeletal level, the species differs from the dwarf cichlids it was historically confused with (Nannacara, Ivanacara, Cleithracara) by having two supraneural bones rather than one and by lacking scales on the preopercle, and from its sister genus Laetacara by a single (uniserial) rather than triple row of predorsal scales.
Sexual dimorphism in Rondonacara hoehnei is poorly documented — the species is known from so few specimens that no detailed account of male–female differences has been published. By analogy with related cichlasomatine dwarfs, males are expected to grow somewhat larger and to carry more produced, pointed dorsal and anal fins, while ripe females are deeper-bodied; but this should be treated as inference rather than established fact for this particular species.
Habitat
Rondonacara hoehnei is endemic to Brazil and to the upper Araguaia River basin, specifically the Rio das Mortes (a major left-bank Araguaia tributary) and the Araguaia itself, across the states of Mato Grosso and Tocantins. Although the Araguaia ultimately drains into the Amazon system via the Tocantins, the fish's actual range lies in the Cerrado — the vast tropical-savanna biome of central Brazil — rather than in lowland Amazonian rainforest. The IUCN assessment treats it as restricted to this drainage; the original 1918 type locality, a tributary of the Araguaia in Mato Grosso, was recorded imprecisely, and for many years the species was effectively known from a single re-collected locality on the das Mortes.
Field data are thin. The fish has been recorded from clear-water streams (Kullander, pers. obs.; Stawikowski & Werner 1998), and the IUCN classifies its habitat as permanent inland rivers, streams and creeks. FishBase summarises the chemical envelope as tropical fresh water of about 64–86 °F with hardness up to roughly 20 dH — figures consistent with the moderately mineralised, near-neutral clear waters typical of Cerrado headwaters rather than the soft, acidic blackwater of the Amazon lowlands. No precise in-situ pH, conductivity or depth measurements have been published for the species; as a small fish of clear streams and creeks it would be expected to occupy shallow water, on the order of the upper metre or two, but this is an inference from habitat type rather than a recorded figure.
Feeding
No direct study of the diet of Rondonacara hoehnei has been published — the species has never been the subject of gut-content or trophic field work. What can be said is general and inferential. FishBase estimates a trophic level near 3.2, placing it among the small omnivores rather than the strict herbivores or piscivores, and assigns it a generalised 'inhabits rivers' ecology. Small cichlasomatine cichlids of this build are typically opportunistic micro-predators and substrate foragers, taking aquatic insect larvae, small crustaceans, worms and other benthic invertebrates from the bottom and from leaf litter, supplemented with algae, detritus and the occasional fallen terrestrial item. In the absence of species-specific data, this guild-level picture — a small benthic omnivore working the substrate and lower water column of clear Cerrado streams — is the most that can be honestly stated.
Mating
The pre-spawning social behaviour of Rondonacara hoehnei has not been described from the wild, and the fish is too scarce in captivity for a documented account of its courtship. What is recorded is that adults exhibit biparental care (FishBase, citing the breeding literature), which in cichlasomatine dwarfs of this kind almost always implies the formation of a monogamous pair that jointly holds and defends a territory through the reproductive cycle. In its sister genus Laetacara and in the superficially similar Nannacara — the genera with which it has most often been compared — pairs form after a period of mutual display, the female typically selecting and preparing a spawning site while the male patrols a wider perimeter. It is reasonable to expect Rondonacara hoehnei to follow this broad cichlasomatine template of paired, site-attached, mutually defended breeding, but the specifics of its courtship, sexual signalling and territoriality remain genuinely unrecorded.
Breeding
Reproduction in Rondonacara hoehnei is documented only at the most basic level: both parents guard the eggs and young (FishBase, Ref. 40602). This biparental care marks it as a guarding cichlid rather than a mouthbrooder, and — given its small size, body form and close relationship to Laetacara — almost certainly an open- or cave-tending substrate spawner that lays an adhesive clutch on a cleaned surface and shepherds free-swimming fry as a pair, the pattern universal among small Cichlasomatini. No published figures exist for this species' clutch size, egg size, hatching time or fry development. Where a number must be stated, the genus-typical range for comparably sized cichlasomatine dwarfs (Laetacara, Nannacara) is on the order of a few dozen to a couple of hundred eggs per spawn; this is offered explicitly as a congener-derived estimate, not a measurement of Rondonacara hoehnei itself, which has — as far as the literature records — never been deliberately bred and reported. The fish's rarity in collections and near-absence from the hobby mean its reproductive biology is one of the larger blanks in its natural history.
In the aquarium
Rondonacara hoehnei is, for practical purposes, not an aquarium fish. It has occasionally reached specialist keepers — a pair photographed in the tank of the German cichlid authority Wolfgang Staeck is among the few hobby records, and the species appears in the German literature (Staeck 2017) — but it is not established in the trade, was never common, and the IUCN explicitly notes it is absent from the current ornamental-fish commerce. Anyone is far more likely to encounter a misidentified Laetacara or Nannacara sold under the name than the genuine article.
No dedicated husbandry account exists, so any guidance is extrapolated from its biology and from close relatives, and should be read in that spirit. As a clear-water stream dwarf of about 3 in, it would suit a well-planted tank of modest size — something in the range of 15–20 US gal for a pair — with fine sand or gravel, leaf litter, driftwood and rock to provide cover and spawning sites, and gentle, well-oxygenated flow. Water should track the recorded field envelope: roughly 75–82 °F, near-neutral pH, and soft to moderately hard water (FishBase tolerates hardness up to about 20 dH), kept clean by regular partial changes. A varied diet of small live and frozen foods — bloodworm, daphnia, brine shrimp, micro-crustaceans — with some prepared foods would match its likely omnivorous, invertebrate-leaning feeding.
Temperament is undocumented but, by the standard of small Cichlasomatini, the species is most safely treated as a peaceful dwarf that becomes territorial around a spawn. A single pair, given a territory and broken sightlines, with peaceful small characins or similar dither fish as the only company, is the sensible default. The honest bottom line is that this is a rarely available, poorly studied fish for the dedicated specialist — keeping it at all is more a matter of conservation-minded husbandry and observation than of established aquarium practice.
Conservation
The IUCN Red List assesses Rondonacara hoehnei as Least Concern (LC), under criteria version 3.1. The assessment was carried out by Brazil's Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio) as part of the national red-listing of Brazilian fauna, last assessed on 7 November 2018 and published in 2022, with P. Reis as reviewer. The justification notes that although the species is known from only about 35 museum specimens — apparently a reflection of how difficult it is to collect rather than of true scarcity — it is regarded as relatively abundant where it occurs, and no significant threats to its population were identified, hence the Least Concern category. The population trend is listed as unknown, it is not recorded from any protected area, and it is not present in the ornamental trade. It carries no CITES listing.
This formal verdict sits in pointed contrast to the view of the authors who re-described the fish. Ottoni and Mattos (2015), working from its then-known restriction to a single locality on the Rio das Mortes and the rapid, large-scale destruction of natural habitat in the region, argued that the species should be considered critically endangered. The tension is real and worth stating plainly: the das Mortes and upper Araguaia lie within the Cerrado, one of the world's most threatened savanna biomes, under intense and accelerating conversion to soy and cattle agriculture, with the attendant siltation, deforestation of gallery forest, and altered stream hydrology. A clear-water stream specialist with a small documented range is, on its face, exactly the kind of fish such pressures endanger. The Least Concern listing reflects the absence of documented population decline and the fish's apparent local abundance; the dissenting expert view reflects the precariousness of a narrow range in a fast-changing landscape. Both deserve to be held in mind when reading this species' status.