Taxonomy & naming
The red-breasted acara was described by the Austrian ichthyologist Johann Jakob Heckel in 1840, in the second volume of the Annalen des Wiener Museums der Naturgeschichte, as Acara dorsiger — one of the many cichlids Heckel named from material brought back to Vienna from Brazil. The type locality is Cáceres (formerly Villa María) on the Río Paraguay in Mato Grosso, Brazil, and the unique holotype (NMW 33669) is preserved in the Naturhistorisches Museum Wien. Over the following century the fish was shuffled through the catch-all genera of the day: Günther listed it as Acara dorsigera in 1862, and it later spent time in Aequidens and Astronotus before its modern placement was settled. In 1986 Sven O. Kullander erected the genus Laetacara to hold a cohesive group of small Cichlasomatinae — the "smiling acaras" — and dorsigera became its type-region congener of the southern basins. The species was given a thorough modern re-description by Felipe Ottoni and Wilson Costa in 2009 (Vertebrate Zoology 59), a paper that also fixed the diagnostic characters separating it from the look-alike Laetacara curviceps and the then newly described Laetacara araguaiae. Kullander's 2003 checklist of South American freshwater cichlids remains the standard nomenclatural authority. Laetacara today contains roughly seven valid species, all confined to South America, and dorsigera is the species that pushes furthest south into the temperate La Plata drainage.
Morphology
This is a genuinely small cichlid. FishBase gives a maximum of 2.5 in standard length, and the Ottoni & Costa re-description measured the largest examined specimen at about 1.5 in SL; an older figure of 3 in total length circulates in the hobby and represents an unusually large, well-fed individual rather than the norm. The body is short, deep and laterally compressed, with the steeply rising forehead and gently rounded snout typical of the genus. Out of breeding dress the fish is a warm brassy-tan to olive, marked with a broken horizontal band running back from the eye, a series of darker vertical bars on the flank, and — diagnostically — a distinct dark blotch set in the middle of the soft dorsal fin, above the fourth and fifth trunk bars. Ottoni & Costa separate dorsigera from its closest relatives by a suite of counts and proportions: 21–22 scales in the longitudinal series, a relatively deep head (head depth 90.2–96.3 % of head length, deeper than in Laetacara curviceps or Laetacara araguaiae), 9–10 dorsal soft rays, 8–9 anal soft rays, 24 vertebrae, cycloid (not ctenoid) scales on the sides of the head, and a wide ectopterygoid bone. The trait that names the fish appears only in spawning condition, when ripe adults of both sexes develop conspicuously red cheeks, opercula and belly — a feature that distinguishes dorsigera at a glance from the otherwise similar Laetacara curviceps, which never reddens. Sexual dimorphism is otherwise subtle: mature males average slightly larger and may carry marginally more pointed, extended dorsal and anal fins, but the sexes are notoriously hard to tell apart outside of breeding.
Habitat
Laetacara dorsigera occupies two distinct chunks of South America. To the north it lives in the upper Madeira system, principally the Río Guaporé (the Río Iténez of Bolivia) along the Bolivia–Brazil border; to the south it is widespread through the Paraná–Paraguay basin of the La Plata system, from the Río Paraguay down the middle Paraná into Argentina, with records also from the upper Río Uruguay in Rio Grande do Sul, Brazil. Eschmeyer's Catalog of Fishes summarises the range as the Paraguay, Paraná and upper Madeira basins across Argentina, Bolivia, Brazil and Paraguay. This is a fish of quiet, marginal, vegetation-choked water rather than open river — slow backwaters, floodplain lagoons, weedy stream margins and the densely planted shallows that fringe larger channels, where it shelters among submerged roots, leaf litter and dense aquatic plants. FishBase records it from rivers and notes an unusual escape behaviour: when pressed it will leap clear of the water to land on floating vegetation, evading aquatic predators at the cost of exposure to birds. Because much of the range lies in the subtropical La Plata system, the species tolerates a wider and cooler thermal band than most Amazonian dwarf cichlids — water temperatures spanning roughly 68–82 °F across the year, with FishBase citing a tropical preference around 68–73 °F. The water it lives in is typically soft to moderately hard and acidic to near-neutral: FishBase lists a pH range of 4.0–7.5 and a hardness range of 1–20 °dH, while Seriously Fish gives 5.0–7.5 and 36–268 ppm. These are shallow-water fish of the marginal zone, usually found within the top metre or two.
Feeding
The red-breasted acara is a small, opportunistic micropredator and forager. FishBase places it at a trophic level around 3.2, and the most reliable accounts describe wild fish as generalists taking algae and organic detritus along with small invertebrates — aquatic insect larvae, worms, micro-crustaceans and other zooplankton — gleaned from the substrate and from among submerged plants and leaf litter. Like its relatives it works the bottom in part by taking small mouthfuls of sediment and sorting edible particles from sand and debris, though it is far less of a dedicated sand-sifter than the larger eartheaters. In its weedy marginal habitat it functions as one of the small benthic invertebrate-feeders that link the leaf-litter and periphyton layers to slightly larger predators above. In captivity this translates into an undemanding, readily fed fish that accepts the full range of small live, frozen and prepared foods.
Mating
Laetacara dorsigera forms monogamous pairs and is, for a cichlid, strikingly peaceable. Outside of breeding a group lives together without much friction, and the species is well known for a rapidly shifting repertoire of colours and patterns that pairs and rivals use to communicate mood second by second. Pair formation is a comparatively gentle affair of mutual display rather than the punishing trials of strength seen in larger cichlids; a compatible pair will stake out and defend a modest territory around a chosen spawning site. The onset of breeding is the moment the fish earns its name — both partners intensify, the cheeks, gill covers and belly flushing deep red — and a normally tolerant pair becomes territorial, driving other fish away from the immediate area of the nest. The aggression is real but proportionate to the fish's small size; it is directed at clearing a defensible spawning patch rather than at dominating the whole tank, and it subsides once the brood is independent.
Breeding
The red-breasted acara is a biparental, open substrate spawner, and it is one of the more reliable New World dwarf cichlids to breed in captivity. A pair cleans a flat surface — a smooth stone, a piece of bogwood or a broad leaf, sometimes the inside of a cave or flowerpot — and the female deposits a single layer of adhesive eggs on it, with reported clutches generally in the range of about 200 to 300 amber-coloured eggs. The division of labour is the classic cichlid pattern: the female tends and fans the eggs directly while the male patrols and defends the surrounding territory, though both parents participate in guarding once the fry are mobile. The eggs hatch quickly, typically within roughly 48 hours to three days depending on temperature, after which the wrigglers are moved to one or more pre-dug pits; they become free-swimming a few days later and are then led about and defended by both parents as a tight school. Newly free-swimming fry are large enough to take newly hatched brine shrimp (Artemia nauplii) and grow steadily onto larger foods. The fish mature young — sexual maturity is reached at only around four months — which, combined with the modest clutch and diligent parental care, makes self-sustaining captive populations easy to establish. Spawning is encouraged by soft, slightly acidic water, a well-planted territory with flat spawning surfaces, and a varied diet of live and frozen foods to bring the pair into condition.
In the aquarium
Laetacara dorsigera is widely regarded as one of the best of the New World dwarf cichlids for a community-minded keeper, and is genuinely beginner-friendly by cichlid standards. A pair can be housed in a tank of around 15–20 US gal, though a larger, well-planted aquarium makes for a more relaxed fish and gives a breeding pair the room to hold a territory without monopolising the whole space. The species is most at home in a mature, stable aquarium furnished to mimic its weedy marginal habitat: a fine, dark sand substrate, plenty of shade and broken sightlines from driftwood, roots, caves and dense planting, and a few flat stones or broad leaves that double as spawning sites. Floating plants to diffuse bright lighting are appreciated.
Water chemistry is forgiving. Soft to moderately hard, slightly acidic to neutral water suits it best — a pH somewhere in the 5.5–7.5 band and modest hardness are ideal, with the softer, more acidic end of the range favouring breeding. Because so much of its native range is subtropical, it tolerates and arguably benefits from a cooler regime than most tropical dwarf cichlids: temperatures in the low-to-mid 20s °C are fine for general maintenance (sources cite ranges as broad as 64–82 °F), and a seasonal cool period can help condition the fish. Filtration should be efficient but the current gentle — these are fish of still and slow water, not of flow — and regular partial water changes to keep nitrate low go a long way, as the species shares the dwarf-cichlid sensitivity to deteriorating water quality.
Feeding presents no difficulty: a rotation of small live and frozen foods (bloodworm, white mosquito larvae, Daphnia, Artemia, Mysis) alongside good-quality flake and small sinking granules, ideally including some plant or Spirulina content, keeps the fish in condition and brings out the red breeding colours. For tankmates, choose peaceful species small enough not to bully the acara yet too large to be eaten — Corydoras and other small catfishes, hatchetfish, pencilfish and medium-sized tetras are classic companions, and the acara will coexist calmly with them outside of breeding. The one caveat is the spawning period: a pair guarding eggs or fry will become territorial and may need the community thinned around them, or the other fish moved, for everyone's comfort. Avoid boisterous, fin-nipping or much larger cichlid tankmates that would intimidate so small a fish.
Conservation
The IUCN Red List assessed Laetacara dorsigera as Least Concern on 20 November 2020 (assessor R.G. Frederico), citing occurrence across Argentina, Bolivia, Brazil and Paraguay; the population trend is recorded as unknown and the assessment lists no major threats specific to the species. As a small, widely distributed and adaptable fish of marginal floodplain and stream habitats, it is not considered to be at risk, and it carries no CITES listing. It is harvested for the ornamental aquarium trade — FishBase notes it as commercially relevant for the aquarium hobby but of no food-fishery interest — at levels that have not raised population concerns. The broader backdrop is the general pressure on the Paraná–Paraguay and upper Madeira systems from agriculture, wetland drainage, dam construction and pollution across the heavily developed La Plata basin; none of these is documented as a present danger to this particular cichlid, but they are the context against which the long-term health of its floodplain habitats should be read.