Taxonomy & naming
Mazarunia pala was described in 2012 by Hernán López-Fernández, Donald C. Taphorn and Elford A. Liverpool, in the journal Neotropical Ichthyology (volume 10, number 3, pages 465–486), as one of two new species in a paper that expanded the genus Mazarunia from a single species to three. The genus had been erected by the Swedish ichthyologist Sven Kullander in 1990 for Mazarunia mazarunii, on the basis of just two specimens; the 2012 revision rested on a far larger series and combined a morphological redescription with a phylogenetic analysis. The holotype of Mazarunia pala (catalogued UG/CSBD 1688, formerly ROM 89675, with many paratypes at the Royal Ontario Museum) was collected from the main channel of the upper Mazaruni River near the mouth of the Kamarang River, in the Cuyuni-Mazaruni region of Guyana. The original combination has stood unchanged since.
Mazarunia sits in the eartheater assemblage of South American cichlids — the tribe Geophagini within subfamily Cichlinae — and the 2012 study formally confirmed its sister-group relationship to Guianacara, another Guiana-Shield genus. The genus is diagnosed by an extraordinary skeletal trait shared with no other cichlid: the complete loss of the sixth infraorbital bone, supported by further details of the epibranchial, palatine, hyomandibula and gill arches. Within the genus, Mazarunia pala is the most readily distinguished of the three species. Phylogenetically it is set apart by the loss of the parhypurapophysis, a small process on the caudal skeleton. Externally it is unmistakable: it is the only Mazarunia with a scaly pad of ctenoid scales at the base of the dorsal fin, it carries only a small suborbital stripe confined to the preopercle, it lacks the clearly discernible vertical flank bars seen in its congeners, and its overall pinkish coloration with a single mid-lateral spot — rather than the dark bars and blotches of Mazarunia mazarunii and Mazarunia charadrica — is itself diagnostic. The three species are partly sympatric within the basin but separable on these colour and osteological grounds.
Morphology
Mazarunia pala is a true dwarf cichlid, the largest of its genus but still a small fish. FishBase records a maximum of 3 in in standard length, and the holotype itself measured 2.5 in SL; this is a fish on the scale of a large Apistogramma rather than a robust eartheater. The body is moderately deep and laterally compressed, and like all Mazarunia it carries the short, low vertical fins that Kullander singled out as a generic hallmark. Fin counts run to about 15–17 dorsal spines followed by 7–8 soft rays, three anal spines and seven anal soft rays, with 26 vertebrae.
Where its congeners are barred and blotched, Mazarunia pala is defined by what it lacks. The base colour is a soft pinkish brown to beige, palest on the lower head, throat and chest. The snout, the region between the rear of the upper jaw and the eye, and the top of the head darken toward brown or grey, and in adults a supraorbital stripe expands with growth into a dark diagonal 'cap' running from the dorsal midline down across the eye toward the corner of the mouth. The gill cover bears a brown-black blotch, strongest dorsally. The body is counter-shaded, each scale outlined in grey to black with a pale centre, so that rows of light spots run along the flank and are most obvious on the caudal peduncle. Seven faint vertical bars are present but variably expressed — vivid in juveniles, often partly retained in adults including the holotype — yet the single consistent, sharply defined dark mark is a spot at mid-body. The fish takes its name from a further detail: a scatter of golden spots behind and below the eye. Sexual dimorphism follows the subtle dwarf-cichlid pattern, with males reaching the larger sizes and developing somewhat more produced fins and ripe females becoming deeper-bodied; the published description emphasises osteology and meristics over strong external sexual characters.
Habitat
Like every member of its genus, Mazarunia pala is bound to one place: the upper Mazaruni River, a headwater drainage of the Essequibo River basin in western Guyana, and it occurs nowhere else. More narrowly still, it is known from only four collection sites strung along the main channel of the upper Mazaruni between the mouths of the Kukui and Kamarang rivers. The upper Mazaruni sits on a highland plateau of the Pakaraima Mountains, ringed by rapids and falls and hydrogeographically isolated from the rest of the Essequibo for millions of years. Ichthyologists who have surveyed it describe a 'lost world' fauna with perhaps the highest proportion of endemic freshwater fishes of any river in the Neotropics, the great majority of its species living in no other river on the planet — and Mazarunia pala is one of those endemics.
The water is among the most extreme of any cichlid's home. All collection sites were blackwater, tea-stained and strikingly soft: the describers measured temperatures of roughly 71–76 °F, high dissolved oxygen of 5.2–9.3 mg/L, an acid pH of about 4.0–4.8 (4.4 at the pala sites), exceedingly low conductivity of 0–10 µS, and none-to-slow currents generally around 0–1 ft/s. Unlike its more bar-flanked congeners, Mazarunia pala occurs mostly in or near the main channel itself, over sandy or slightly muddy substrates structured by submerged or emergent grass, other riparian vegetation and some driftwood. It was frequently caught along artificial 'tailings' beaches deposited by gold-mining dredges, where transparency drops to a few tenths of a metre. By night, like the other species, it appears to move into shallow, flooded banks thick with terrestrial vegetation.
Feeding
No dedicated dietary study of Mazarunia pala has been published — it has been collected and described far more than it has been watched feeding — but its anatomy and relationships mark it out as a small benthic invertivore. FishBase models place it at a trophic level near 3.2, the value typical of a small carnivore that works the bottom for aquatic insect larvae, micro-crustaceans and other small invertebrates rather than rasping algae or sifting large mouthfuls of sediment in the manner of the big eartheaters. Its lower pharyngeal jaw carries enlarged, molariform posteromedial teeth, hinting at a capacity to crush harder prey items.
In a tea-coloured, nutrient-poor highland river the available menu is dominated by the larvae of midges, mayflies and other stream insects, the staple of most small Guiana-Shield fishes. Working the sandy main-channel margins and the submerged grass and driftwood among which it shelters, Mazarunia pala can be assumed to forage opportunistically over the substrate and structure of its blackwater home, picking small invertebrates from sand, leaf litter and submerged vegetation.
Mating
As a small substrate-spawning geophagine, Mazarunia pala almost certainly forms pair bonds around a defended site rather than holding a harem or schooling to spawn, but the fine detail of its courtship has not been documented — in the wild or in captivity. The species is so newly described and so rarely encountered that no behavioural study exists, and what can be said is extrapolated from its body plan, its close relatives and the general biparental template of the tribe Geophagini.
Mazarunia are not strongly aggressive cichlids, and at this dwarf size any territorial disputes are correspondingly small in scale, played out over a patch of streambed rather than a large arena. The vivid juvenile barring that fades in adults, the dark adult head 'cap', and the golden suborbital speckling are all plausibly signals used in social and reproductive interactions, but their role in courtship has not been described. Pair formation, colour signalling and the division of labour between the sexes remain, for this species, essentially unstudied.
Breeding
Breeding has not been documented for Mazarunia pala, either in the wild or in aquaria, and no account of its eggs, clutch size, incubation time or fry development has been published. On the strength of its relationships, it is expected to be a biparental substrate spawner like its congener Mazarunia mazarunii — depositing eggs on a sheltered surface or in a small cavity, with both parents guarding and fanning the clutch and then shepherding the free-swimming young among the structure of the streambed.
A precise clutch count is therefore not available. As a fish around 2.5–3 in long it would lay a small clutch in keeping with its size; genus-typical figures for these dwarf substrate spawners run on the order of a few dozen to perhaps a hundred or so eggs per spawn, rather than the hundreds or thousands of a large eartheater, and that is the most that can honestly be said. The blackwater main-channel habitat — soft, acidic, well-oxygenated and structured by grass and driftwood — supplies the kind of sheltered surfaces such a fish would use, but the actual reproduction of this remote endemic remains to be observed and described.
In the aquarium
Mazarunia pala is, for all practical purposes, not an aquarium fish. It was described only in 2012, has no established presence in the ornamental trade, and there is no body of hobbyist experience to draw on; any keeping advice is necessarily extrapolated from its biotope and from the handful of accounts of its better-known congener Mazarunia mazarunii. Should it ever reach a specialist's tanks, it would have to be treated as a small, soft-water blackwater dwarf and a conservation-minded project rather than a community fish.
The defining challenge would be the water. Few cichlists ever keep fish from water this extreme: the species lives at pH around 4.0–4.8 with conductivity of just 0–10 µS — barely-mineralised, blackwater so soft that ordinary tap water is wildly out of range. Replicating it would mean reverse-osmosis or rainwater acidified and stained with leaf litter, peat and botanicals, run warm (roughly the low-to-mid 20s °C, matching the documented 71–76 °F) and kept very clean, since such soft water has almost no buffering capacity and pH can crash without care. A modest footprint would suffice — adults top out near 3 in, so a tank in the region of 23.5–31.5 in (roughly 20–30 US gal) is ample for a pair — over fine sand, with submerged grass, driftwood and leaf litter recreating the structured main-channel margins it favours and the small cavities a substrate spawner would use.
Feeding would be straightforward in principle: small live and frozen foods (bloodworm, daphnia, micro-crustaceans, baby brine shrimp) suit a small benthic invertivore, supplemented with quality micro-pellets. Tankmates, if any, should be small, peaceful soft-water companions; this is emphatically not a fish for boisterous communities. The real obstacles are availability and water chemistry, not temperament — and given the species' Endangered status, wild-collected stock should be approached with particular caution.
Conservation
The IUCN Red List assesses Mazarunia pala as Endangered (EN), under criterion B1ab(iii), in an assessment dated 1 November 2023 and published in 2024 by D.C. Taphorn and D. Rodríguez-Olarte; the population trend is recorded as unknown. The listing is driven by the fish's minuscule, single-channel range: the assessors give an extent of occurrence of just 34 mi², restricted to four threat-defined locations in the uppermost Mazaruni drainage — an 'area of extreme endemism,' in the words of Alofs and colleagues — that currently has no formal protection.
The specific threat is gold. The upper Mazaruni is the scene of extensive, largely illegal open-pit and river-dredge gold mining, alongside deforestation for agriculture. Because Mazarunia pala lives in the main river channels themselves, it is directly exposed to the sediment those operations release: silt smothers the benthic communities that sustain this and every other river fish, and the describers in fact caught the species along the artificial tailings beaches the dredges leave behind. These pressures are judged to be causing a continuing decline in habitat quality, the basis for the Endangered listing. The human population of the region is small but steadily increasing. Researchers including López-Fernández and Taphorn have repeatedly urged formal protection for the upper Mazaruni — a reserve or national park, regulated mining, controls on deforestation and flow alteration — to safeguard a fauna in which the great majority of species, this little gold-spotted cichlid among them, exist nowhere else on Earth.