Taxonomy & naming
Bujurquina eurhinus was described by the Swedish ichthyologist Sven O. Kullander in 1986, in his monograph Cichlid Fishes of the Amazon River Drainage of Peru — the same 394-page work in which he erected the genus Bujurquina itself (type species Bujurquina moriorum) to hold an assemblage of small, biparentally custodial "primitive" (delayed) mouthbrooding acaras that had previously been lumped into Aequidens. The holotype (ANSP 158173, Academy of Natural Sciences of Philadelphia) and a long series of paratypes came from the Río Hospital, in the Río Madre de Dios drainage of Cuzco Department, Peru, at roughly 12°53'S, 71°27'W. The Catalog of Fishes lists no synonyms; the name has stood unchallenged as Bujurquina eurhinus Kullander 1986 in every subsequent treatment, including Kullander's own checklist contribution in Reis et al. (2003) and recent phylogenetic and ecomorphological work by Říčan and colleagues. The genus has continued to grow — currently around eighteen valid species, most of them western-Amazonian — and Bujurquina eurhinus belongs to the southern, same-coloured-lipped lineage of the genus (its congeners in the northern group often have a bright azure lower lip). Paul Loiselle, who built an aquarist's identification key to the Peruvian species, grouped eurhinus with the thick-lipped Bujurquina tambopatae and Bujurquina labiosa, separating it from tambopatae by its prominent upper lip and its plain, streamer-less tail. (Family placement is in slight flux between sources: FishBase files the genus under Cichlasomatinae while the Catalog of Fishes uses Cichlinae — a labelling difference, not a dispute about the fish.)
Morphology
This is a small cichlid. The maximum recorded length is about 3.5 in in standard length (snout to tail base), so even a large adult is a palm-sized fish, deeper-bodied and more compact than the slender lowland members of the genus — a build Říčan et al. (2023) read as an adaptation to fast, upland water. Its defining feature is the one the name advertises: thick, well-developed lips and an unusually prominent, protruding upper lip that give the snout a bulbous, "well-nosed" profile (Greek eu, well or big, plus rhinos, snout). In Loiselle's key the species keys out by that prominent upper lip combined with light dorsal-fin lappets — pink to red in life — edged by a single narrow dark submarginal band, a caudal peduncle measuring 12.5–15.7% of standard length, and a caudal fin that is subtruncate to only slightly notched, lacking the long filamentous "streamers" that trail from the tail of its close relative Bujurquina tambopatae. Like other Bujurquina it carries the genus's signature markings: a midlateral blotch and a dark lateral band running back along the flank, a dark bar through the eye, and a faint suborbital stripe. No formal description of sexual dimorphism in eurhinus has been published, but the pattern is consistent and strong across the genus, so it almost certainly applies here: males grow somewhat larger, develop longer-extended soft dorsal and anal fins (and, in many species, trailing caudal filaments and a slight nuchal hump), while ripe females are smaller, plumper and plainer. Treat that as a genus-typical inference rather than a measured fact for this species.
Habitat
Bujurquina eurhinus is endemic to the upper Madeira system on the eastern slope of the Andes. FishBase and Kullander's monograph place it in the Madre de Dios drainage of Peru — the Pilcopata, upper Madre de Dios, Manú, Colorado and Marcapata rivers — and the IUCN assessment extends the range into the upper Yurúa basin in Peru and the Acre and Beni basins of Bolivia, making it a Peru–Bolivia species rather than a strict Peruvian endemic. It is a piedmont fish. Říčan et al. (2023) characterise the "highland" Bujurquina, eurhinus among them, as occupying Andean-foothill streams and rivers roughly between 400 and 1,656 ft elevation — clear, permanently running water over beds of stones and pebbles, seasonally turbid in the rains. The IUCN account, drawing on different field data, summarises its habitat more bluntly as "white-water streams and rivers," reflecting the sediment-laden runoff these Andean tributaries carry in flood; the two descriptions are best read together as a clear-to-turbid, flowing, gravel-bottomed piedmont stream rather than the still blackwater of the lowland Amazon. No detailed in-situ water chemistry has been published specifically for eurhinus. Given the geology of these foothill rivers and the parameters reported for the genus by keepers, the water is warm and near-neutral — roughly 75–82 °F and pH about 6.5–7.5 — and the species lives in the shallow, wadeable margins of small rivers (on the order of 0–7 ft deep); both the chemistry and the depth band are reasoned habitat/genus-typical estimates flagged as such, not measurements taken from this fish.
Feeding
No gut-content study has been published for Bujurquina eurhinus, so its diet is inferred from its anatomy, its genus and its habitat. FishBase estimates a trophic level of about 3.5, squarely in the range of a small carnivore-leaning omnivore. Bujurquina are benthopelagic foragers of small prey — aquatic insect larvae and other invertebrates, micro-crustaceans, plus algae, biofilm and organic detritus worked from the substrate and from leaf litter and submerged wood. In a fast, stony foothill stream that menu skews toward the drifting and clinging invertebrate fauna of running water — caddis, mayfly and midge larvae and the like — gleaned from gravel and crevices. The conspicuously thick lips that give the fish its name are a plausible foraging asset for picking prey from rocky surfaces, though that functional link has not been tested. In its community it is a small, mid-level insectivore-omnivore, not a specialist.
Mating
Reproductive behaviour has not been documented in the wild for Bujurquina eurhinus specifically, but Bujurquina are among the better-studied small Neotropical cichlids as a group, and the pattern is consistent and distinctive. They are monogamous, biparental and pair-bonding: a male and female form a stable pair and jointly hold and defend a territory through courtship and into spawning. Compared with the substrate-guarding eartheaters they resemble, Bujurquina are mild-tempered fish — keepers of the well-known Bujurquina vittata describe a nervous, fast-moving but non-aggressive cichlid that troubles tankmates little — with the partners' energy directed at defending the clutch rather than at conspecific warfare. Pair formation can take time and is not guaranteed from any random grouping; one published account of breeding the related Bujurquina vittata describes keeping several fish together until a male and a single female paired off and began driving the others away, at which point the spare fish had to be removed for their safety. That dynamic — let a group sort itself into a pair, then separate the rest — is the practical reality of getting these fish to spawn.
Breeding
The genus's calling card is its breeding mode, and it is genuinely unusual: Bujurquina are biparental delayed mouthbrooders. Rather than spawning on a fixed stone or in a cave, the pair lay their adhesive eggs on a movable object — a fallen leaf, a strip of bark, sometimes a loose piece of substrate — that they can physically pick up and relocate, towing the whole clutch to safety in response to a predator or a change in water level. After the eggs hatch (or shortly before), the parents take the wrigglers into their mouths and brood them orally for several days, releasing the free-swimming fry to forage under guard and gathering them back into the mouth at any threat or at nightfall. In the well-observed Bujurquina vittata the male typically takes up the brood first and carries it for about five days before sharing or ceding the duty to the female — what George Barlow termed the "cedocavus" (cede-mouth) mode — a male-first delayed mouthbrooding strategy unusual among cichlids. Clutch sizes for the genus are modest: Bujurquina vittata lays up to roughly 300–400 eggs on a leaf, and eurhinus, a smaller fish, very likely produces fewer; no clutch count has been published for eurhinus itself, so that figure is a genus-typical reference rather than a measured value. Captive spawnings of congeners come on a diet rich in live foods with stable, soft, near-neutral water; the parents are attentive but skittish, prone to abandoning or eating a first brood if disturbed, and keepers report screening the tank and minimising water changes while a pair is holding. Parental care is biparental throughout — both fish brood, both guard, and the fry are tended for a couple of weeks before independence — but the full leaf-carry-then-mouthbrood sequence has been documented in relatives, not yet formally in eurhinus, which has essentially never been kept.
In the aquarium
Bujurquina eurhinus is, for all practical purposes, unknown in the hobby. It has never appeared in the commercial trade and no dedicated keeper accounts exist for this species specifically; what follows is built from the well-documented requirements of its closest congeners — particularly Bujurquina vittata, Bujurquina tambopatae and the other Peruvian Bujurquina — flagged where they are genus-typical inferences rather than observations of eurhinus itself. The general approach for any Bujurquina applies here: treat it as an acara-grade cichlid that is smaller and more delicate than it looks, and give it stable water over showy water volume.
A pair can be housed comfortably in a 25–30 US gal tank (roughly 90 × 15.5 in footprint), though more space is always an asset when the fish are holding and the pair begins driving each other into corners. The bottom should be fine sand or a mix of fine sand and small rounded pebbles — a nod to the gravel-bedded piedmont streams these fish come from — with a thick layer of dried leaves (Indian almond, oak, beech) scattered across it. Leaf litter is not decorative here; it is a functional component of the tank. Bujurquina need a loose, movable leaf on which to deposit their eggs, and the pair will select and prepare one before spawning. Add several smooth, flat stones and one or two pieces of waterlogged wood or cork bark to provide visual breaks and bolt-holes, and keep the lighting subdued — this is a fish of shaded stream margins, and a brightly lit open tank produces nervous, washed-out fish. Moderate, gentle filtration (a sponge filter or a canister set to a soft, diffuse flow) suits a small piedmont stream better than strong directional current.
Water chemistry should mirror the soft-to-neutral conditions of the upper Madeira watershed: 75–82 °F, pH 6.5–7.5, and soft to moderately hard water (under about 12 °dH). These parameters are not difficult to hit in most regions with reasonable tap water; if your water is hard and alkaline, a proportion of reverse-osmosis water will bring it into range. Weekly water changes of 20–30% are important for any small cichlid, but do them gently and with temperature-matched water when the fish are actively brooding, since the disturbance of a water change is one of the main triggers for a nervous pair to swallow or abandon a first brood. Feed a varied diet: a quality small-pellet or flake staple, supplemented several times a week with frozen or live bloodworm, daphnia, cyclops and small brine shrimp — a diet that mimics the invertebrate drift of a running stream and keeps the pair in good breeding condition.
Bujurquina are peaceful cichlids outside of active breeding. They will not trouble small, non-cichlid tankmates: small tetras and pencilfish, Corydoras and dwarf Loricariids, and similarly sized characins from Amazonian blackwater or clearwater are all reasonable companions, with the caveat that any fish sharing the tank will be chased vigorously when the pair is tending eggs or mouthbrooding. A biotope approach — a small group of Hyphessobrycon or Moenkhausia tetras as dithers, a couple of Corydoras trilineatus or similar on the bottom, and a pair of Bujurquina as the centrepiece — replicates the community structure of a western-Amazon piedmont stream and produces visually coherent, behaviourally settled fish. Avoid combining with large or aggressive cichlids; Bujurquina are not fighters and will be bullied.
The most common keeper mistake with this genus is rushing breeding by disturbing the tank. Pairs are attentive parents but genuinely skittish: bright lights, heavy water changes, banging on the glass or persistent harassment from other fish during the brooding period will cause the pair to swallow or desert the brood. For a first attempt, strip the tank down to the pair plus a few small dither fish, screen the front glass lightly so you can observe without being seen, and do only the minimum maintenance until the fry are free-swimming. Because eurhinus is essentially unavailable commercially, any fish that do appear in the hobby should be considered captive-bred specimens sourced from serious Neotropical cichlid enthusiasts — the American Cichlid Association or European Cichlid Association networks are the realistic places to find them. Their rarity means patience with early brood losses is unavoidable; most Bujurquina get their technique wrong on the first one or two spawns, and a well-matched pair in a settled, undisturbed tank will usually sort itself out within a few breeding cycles.
Conservation
The IUCN Red List assesses Bujurquina eurhinus as Least Concern (assessed 25 April 2014 by J. Sarmiento and E. Correa, published 2016), on the grounds that it is widely distributed across several Peruvian and Bolivian foothill basins, appears to be common, has a stable population and occurs in protected areas — in Peru it is recorded from Manú National Park and the Amarakaeri Communal Reserve, and the assessors estimate that on the order of a fifth to a third of its range falls within protected land. It carries no CITES listing and has only "potential" rather than active ornamental-trade value; its remoteness from Iquitos, the centre of Peru's aquarium-fish export, keeps it out of commerce almost entirely. The one specific threat the assessment flags is gold mining: artisanal and commercial alluvial gold extraction is intense and expanding in the Madre de Dios region, and where it operates it tears up streambeds, loads rivers with sediment and contaminates them with mercury — directly degrading the clear, gravel-bottomed piedmont habitat this fish depends on. So while the species itself is not currently of conservation concern, its core range sits inside one of the Amazon's most active deforestation-and-mining frontiers, and a localized, gravel-stream specialist is exactly the kind of fish that loses ground first when those rivers silt up. The assessment is now more than a decade old and flagged by IUCN as needing updating, so its reassuring conclusion should be read with that caveat.