Taxonomy & naming
Apistogramma pleurotaenia was described by the British ichthyologist Charles Tate Regan in 1909, originally in the genus Heterogramma — a name Regan used for several small South American cichlids that were later folded into Apistogramma. The description rests on a single specimen, the holotype, now held in the Natural History Museum, London, under the register number BMNH 1909.2.25.61. No paratypes and no subsequently confirmed material extend the type series; the species is, in the standard phrasing of FishBase and the reference databases, "known only from the holotype."
The type locality is the crux of the problem. Regan's specimen was an aquarium import labelled "Río de La Plata, South America," which would place it in the Paraná–La Plata system shared by Argentina, Uruguay, Paraguay and southern Brazil. But Eschmeyer's Catalog of Fishes records this label as erroneous — an aquarium-import locality — and as of its 2026 update no longer hedges: it now carries the species' current-status distribution outright as "South America: Rio Guamá drainage, Belém, Brazil," northern Pará, reasoning from what was actually being exported through the ornamental trade at the time rather than from any field record. FishBase, following Kullander's 2003 checklist treatment, still lags this revision and carries the distribution simply as "Argentina (known only from the holotype)," taking the original label more or less at face value and even classifying the fish's climate as subtropical. The two leading authorities therefore place the fish in opposite halves of the continent, and neither can resolve it, because there is no second specimen to check — though the taxonomic catalog's revised reading now tips the balance toward Belém.
The net result is a name in taxonomic limbo. Apistogramma pleurotaenia is treated as a valid species by the Catalog of Fishes and FishBase — the catalog lists it as valid, citing Kullander (2003), Staeck (2003, 2017), Römer et al. (2013), Mirande & Koerber (2015) and Morgenstern (2024) — but it is also widely regarded as poorly known and possibly dubious, the kind of single-specimen, vague-locality cichlid that cannot be confidently matched to any living population and may eventually prove to be a synonym of, or simply unidentifiable against, a better-known apisto. No common name is genuinely established for it in the hobby or trade; aggregator databases attach the label "Chequered Dwarf Cichlid," but the fish is not a trade animal and that name has no real currency, so this profile lists none.
Morphology
What is known of the morphology comes entirely from the single holotype and Regan's original account, so the description is narrow and not backed by any series showing natural variation. The fish is small even by the standards of a genus of dwarfs: FishBase gives a maximum of about 1 in standard length for the (male/unsexed) type, with a figure of around 2 in cited for females — though with only the one specimen in hand, the female figure should be read as a genus-typical estimate rather than a measured value.
The epithet records the single most conspicuous feature Regan saw: pleurotaenia, from Greek pleura ("side, flank") and taenia ("band, stripe"), means "side-striped," referring to a dark lateral band running from the eye to the base of the caudal fin. That midlateral stripe is the diagnostic mark the name memorializes. Beyond it, the body is the compressed, moderately elongate shape typical of Apistogramma. Because the species is known from a faded, preserved holotype rather than living fish, almost nothing reliable can be said about coloration, iridescence or breeding dress, and sexual dimorphism has never been observed in life — it can only be inferred from the near-universal pattern in the genus, in which males grow larger and longer-finned and females turn yellow with black markings when brooding.
Habitat
No wild ecological data exist for Apistogramma pleurotaenia. The species has never been studied in the field, because no one can say with confidence where it lives. The only locality information is the disputed "Río de La Plata" label on the holotype — which the Catalog of Fishes treats as an erroneous aquarium-import label and, in its 2026 update, now refers outright to the Rio Guamá drainage at Belém in northern Brazil, while FishBase still reports it at face value as Argentina. Any coordinates attached to this profile are therefore a deliberately rough placeholder, not a real collection point: they should be read as a flag for "disputed historic locality (catalog: Belém, Pará; FishBase: 'Argentina'/La Plata)" rather than as a documented occurrence.
Everything else is inferred from the genus. Apistogramma are fishes of warm, soft, often acidic Neotropical lowland waters — small forest creeks, stream margins, flooded litter and backwaters — where they live close to the bottom among leaf litter, submerged wood and root tangles. If Apistogramma pleurotaenia is a real Paraná–La Plata animal it would be one of very few apistos that far south, in cooler subtropical water; if (as the Catalog of Fishes suspects) it actually came from the Belém area, it would belong to the warm, blackwater-influenced lowland Amazon fauna instead. The honest position is that its biotope is unknown. FishBase records no measured depth, temperature or pH for the species. The water figures shown on this profile are therefore not data but deliberately flagged basin-typical placeholders, pegged to the locality the Catalog of Fishes now treats as most-supported — its 2026 update gives the distribution as the Rio Guamá drainage at Belém, the warm soft acidic eastern-Amazon lowland (roughly 75–84 °F, pH about 5.0–6.5) where the genus is at home. Were FishBase's lagging 'Argentina'/Paraná reading correct instead, the envelope would shift cooler (around 64–79 °F, pH 5.5–7.2, like the far-south Apistogramma borellii). No depth is recorded or inferable. Read every one of these numbers as a hedge, not a measurement.
Feeding
There are no diet data for Apistogramma pleurotaenia — no stomach-content study, no field observation, nothing beyond the dead holotype. What can be said is what holds for the genus as a whole: Apistogramma are benthic micropredators, small bottom-oriented hunters that take mouthfuls of substrate and leaf litter and pick out aquatic insect larvae (especially midge and other dipteran larvae), micro-crustaceans, worms and other tiny invertebrates, sitting at a trophic level around 3 as carnivores of small prey. In its litter community such a fish would be both predator and forage, eaten by larger cichlids and characins — the ecological pressure that, across the genus, favours small size, cryptic patterning and intensive brood care. All of this is inference from the genus, not a record for this species.
Mating
The pre-spawning behaviour of Apistogramma pleurotaenia has never been observed; the species has not been kept or bred, so its social structure and courtship are entirely unknown. By analogy with the genus, one would expect a polygamous or casually harem-based system in which a male holds and patrols a larger territory overlapping the smaller spawning territories of one or more females, with the female committing to a cave and leading a chosen male to it to spawn — but this is a genus-level expectation projected onto the species, not anything documented for pleurotaenia itself.
Breeding
Breeding has never been documented for Apistogramma pleurotaenia in the wild or in captivity. The only reproductive note in the databases is a genus-typical generalization, carried by FishBase: like other Apistogramma it is presumed to be a cave-spawning substrate brooder in which eggs are attached to the ceiling of a cavity and the female cares for the eggs and larvae while the male holds the surrounding territory. That statement should be read strictly as an inference from the genus, flagged as such. There are no observed clutch sizes for pleurotaenia: the fact box's ~40–80 eggs is a genus-typical estimate (small cave-spawning Apistogramma commonly lay clutches in roughly the 40–200 range, with the smallest dwarfs at the low end), pinned to this fish's very small ~1 in size and FishBase's low-fecundity resilience note, not a measured value. Likewise there are no fry-development data and no spawning triggers for this particular species, and given that it is known from one specimen of uncertain origin, there may never be.
In the aquarium
Apistogramma pleurotaenia is not a kept species. It has never appeared in the aquarium trade under its own name, and because the holotype — the only specimen ever assigned to this name with any confidence — is a century-old preserved fish of disputed origin, there is no captive population to draw husbandry notes from. Any keeper who claims to have maintained Apistogramma pleurotaenia should be viewed with healthy skepticism; the fish cannot currently be identified from a living specimen. This profile can offer only what genus-typical Apistogramma husbandry suggests would apply, and it says so plainly throughout.
Should the species ever be properly collected and assigned to living fish, general regani-group Apistogramma practice would be the starting point. The water figures on this profile are inferred from the Belém/eastern-Amazon locality that Eschmeyer's Catalog of Fishes now treats as most-supported: warm (75–84 °F), soft and acidic (pH 5.0–6.5), with hardness kept low — ideally under 6–8 °dH. Reverse-osmosis water cut with a small fraction of tap, or naturally soft source water, fits the bill. Brown-stained tannin-rich water from dried Indian almond or oak leaves would further replicate the black-water aesthetic of such habitats and appears to reduce stress in regani-group Apistogramma generally. A heavily planted or leaf-littered tank with a fine sand substrate and a scattering of small coconut-cave spawning sites is the format these fish are adapted to. Dim lighting suits them; surface cover from floating plants reduces skittishness.
A 60-litre tank (roughly 60 × 30 × 12 in) is the practical minimum for a single pair; a slightly longer tank gives enough horizontal territory for a small harem of one male and two females. Apistogramma pleurotaenia would be a very small fish — the holotype male appears to run around 1 in standard length, making it among the smaller apistos — so volume requirements are modest, but sight-line breaks are important because males harass females outside of spawning periods. If kept as a harem, multiple cave options spaced well apart allow females to retreat to their own spawning territories. Tankmates should be small, peaceful and mid-to-upper water column — pencilfish, small tetras or dwarf corydoras are the standard dither-fish choices for this kind of setup; larger or boisterous fish stress cave-spawning dwarfs and risk eating fry. Other dwarf cichlid species should not be mixed in the same tank.
Sexing follows the near-universal Apistogramma pattern: males would grow substantially larger than females and carry extended unpaired fin filaments; females in breeding condition turn bright canary yellow with a black cheek patch and broken lateral stripe, colour that in this species would presumably be built around the dark midlateral band the epithet describes. Neither has been observed in life, so these are projections from the genus rather than records. The spawning sequence, where documented in the wider genus, involves the female leading the male to a cave, spawning on the cave ceiling, and then taking sole custody of eggs and larvae while the male defends the outer territory — a pattern that requires the keeper to offer multiple sheltered spawning caves and to accept that the female may turn combative toward the male once fry are free-swimming. Fry of small regani-group Apistogramma are typically large enough at first swim to take freshly hatched Artemia nauplii or microworms, with infusoria and green water as a supplement.
The common keeper mistake with any rarely available, poorly known Apistogramma is to assume that a fish sold as the species actually is the species. The regani group contains a number of similar, partly overlapping taxa and trade fish are often mislabelled or unidentified. Anyone genuinely interested in keeping near-relatives of Apistogramma pleurotaenia — fish from the eastern-Amazon Belém region — should prioritise confirmed locality data and acquire from specialist breeders who can document provenance, not from general retail. Until a second specimen is collected and the species is formally redescribed from living material, Apistogramma pleurotaenia belongs in the category of names to know rather than names to keep.
Conservation
Apistogramma pleurotaenia has not been evaluated by the IUCN Red List; its status is Not Evaluated (NE), as confirmed by FishBase and by the absence of any species page on the Red List. This is unsurprising for a taxon known from a single century-old specimen with no reliable locality: there is no population to assess, no range to map, and no trend to measure. It carries no CITES listing, and because it is effectively unknown in the aquarium trade, it faces none of the collection pressure that touches the popular apistos.
The honest conservation story is that there is no story — only a data gap. Whatever wild population Apistogramma pleurotaenia might correspond to, if any, would share the generic pressures on Neotropical lowland streams (deforestation, agriculture, sedimentation and water-quality decline), and if the fish really is a Paraná–La Plata endemic, those southern subtropical waters carry their own burden of damming, pollution and introduced species. But none of this can be pinned to pleurotaenia in particular. The single most useful thing that could happen for this name is not a conservation action but a taxonomic one: fresh collecting and a modern redescription that either rediscovers the fish, fixes its true locality, or formally retires the name.