Taxonomy & naming
Satanoperca setepele was described in 2021 by Renata Rúbia Ota, Gabriel de Carvalho Deprá, Sven O. Kullander, Weferson Júnio da Graça and Carla Simone Pavanelli in the journal Neotropical Ichthyology (volume 19, issue 4). The holotype — an adult of 6 in standard length, catalogued as NUP 13671 in the Nupélia collection at the Universidade Estadual de Maringá — was taken in 2011 from lago Japonês, a floodplain lake tributary to the Rio Araguaia near Nova Crixás in the state of Goiás. The genus Satanoperca Günther, 1862 holds nine species split into two groups: the daemon group (Satanoperca acuticeps, Satanoperca daemon, Satanoperca lilith), distinguished by bold round black blotches on the flank and high meristic counts, and the jurupari group, which lacks those blotches and runs to lower counts. Satanoperca setepele belongs squarely to the jurupari group. The authors diagnosed it from the superficially similar Satanoperca curupira (its nearest look-alike, from the Rio Madeira) by having only two oblique stripes on the lachrymal bone rather than three to seven, a clean cheek and operculum free of dark stripes, a conspicuous longitudinal body band that persists in preserved fish, and a higher gill-raker count (15–19, modally 18, on the first ceratobranchial versus 14–16). It is separated from Satanoperca leucosticta and Satanoperca mapiritensis by the absence of small light spots on the head, and from Satanoperca pappaterra by the way its dorsal melanophore patches blend seamlessly into the flank bars. The specific name is registered in ZooBank under act 128E9A30-4451-4AA5-B960-B92192C6EF4A.
Morphology
This is a medium-sized eartheater. The largest measured specimen, the holotype, reached 6 in standard length (about 6 in SL, or roughly 7–8 in in total length once the tail is counted), and the type series ran from small juveniles of around 3 in to adults near 5.5 in SL — so it is a smaller fish than the demon eartheater Satanoperca jurupari proper, which can approach 10 in. The body is the classic Satanoperca shape: moderately deep and laterally compressed, with the steeply sloping forehead and protrusible, sand-shovelling mouth shared across the eartheater radiation. In life the ground colour is greenish over a yellowish-white belly, the upper head and lip dark brown, and the cheek and gill cover washed greenish to pale beige; preserved fish fade to pale beige or yellowish-brown. The diagnostic head marks are two dark-brown oblique stripes crossing the lachrymal (the bone between eye and upper lip), one along its upper margin and one along its lower, with the cheek and operculum otherwise free of dark striping. Down the flank run six to seven dark bars that merge with a matching series of dorsal melanophore patches — the lower bars often Y-shaped where they branch — overlaid by a conspicuous dark-brown longitudinal band concentrated along the upper lateral-line scale row. The unpaired fins are pale with rows of small white spots on the soft dorsal and anal, and the caudal fin carries a black, usually ocellated blotch at its base. There is no obvious colour difference between the sexes. Body shape and fin filaments offer only a weak guide to sex: breeding males tend to be deeper-bodied with longer filamentous extensions to the dorsal and pelvic fins, but the describers cautioned that not every deep-bodied, long-finned fish proved to be male on dissection.
Habitat
Satanoperca setepele is native to the Rio Tocantins basin of central-eastern Brazil, including its largest tributary, the Rio Araguaia. Confirmed native localities span the basin from the Rio Cristalino and the Cocalinho region on the upper Araguaia, through the Serra da Mesa reservoir on the Rio Tocantins near Niquelândia, downstream to the mouth of the Rio Itacaiúnas near Marabá — a range crossing the states of Goiás, Mato Grosso, Tocantins and Pará. A second, introduced population is established far to the south in the upper Rio Paraná floodplain, where the fish is non-native; much of what is known about its ecology actually comes from long-term floodplain surveys there. Within both ranges it is a fish of slow and still waters: it is rare in the open river channel and most frequent in permanent and temporary floodplain lagoons and natural connecting canals, and tagging work in the upper Paraná found it to be sedentary, making only short local movements. The Tocantins-Araguaia is a clearwater system, and these eartheaters favour the soft, warm, sandy-bottomed shallows typical of lowland Neotropical floodplains. Precise in-situ chemistry was not published with the original description, but congeners of the jurupari group are recorded from soft, slightly acidic to neutral water (roughly pH 5.5–7.0) at tropical temperatures of about 77–84 °F, and Satanoperca setepele can be expected to occupy the same envelope. As a shallow-water floodplain and littoral fish it lives within the top metre or two of the water column rather than at depth.
Feeding
Like all eartheaters, Satanoperca setepele earns its keep at the bottom. It takes mouthfuls of sand and fine sediment, sieves them through the gill rakers — of which it has an unusually high count for the group — to strain out edible particles, and ejects the cleaned grains. Stomach analyses of the introduced upper-Paraná population (Hahn and colleagues, 1997 and 2004) found that detritus dominated the diet, making up roughly 30–60 percent of the gut contents by frequency, with aquatic and terrestrial insect larvae, mollusks and fragments of higher plants taken less often. That places the species low on the food web as a benthic detritivore and invertivore rather than a predator. Its constant winnowing of the substrate makes it, like its relatives, a minor sediment engineer in the soft-bottomed lagoons it inhabits, turning over the top layer of sand as it forages and recycling buried organic matter and small invertebrates back into the community.
Mating
Reproduction in Satanoperca setepele is biparental and built around external fertilization followed by mouthbrooding, but the courtship and pair-bonding behaviour was not directly observed in the original study and has to be inferred from the closely related jurupari-group eartheaters. In those fish, ripe adults form pairs and clear and defend a patch of open sand or a flat surface on which the eggs are laid before the parents take them up into the mouth. Reproductive data gathered from the upper-Paraná population show that Satanoperca setepele breeds in the warm-water months, from October through January, with the peak share of ripe fish in December and January, and that it spawns in both still lagoon habitats and flowing-water stretches (breeding activity was actually a little higher in the lotic, flowing sites). Females mature small: the median length at first maturity is about 3.5 in SL in females and 3 in in males, and essentially all fish are mature by about 4.5 in — so this is a fish that begins breeding well before reaching full size. An unusual wrinkle reported for the species is that it appears to be a non-functional protogynous hermaphrodite: some males carry undeveloped oocytes in the gonad, yet no actual sex change was ever observed, so the trait has no reproductive consequence.
Breeding
Satanoperca setepele is a larvophilous biparental mouthbrooder — the strategy that characterises the jurupari species group and sets these eartheaters apart from substrate-guarding cichlids. The eggs are fertilized externally on the substrate and guarded there in the open for the first day or two; once they hatch, the larvae are gathered into the mouth of one or both parents and carried until they are well developed, then released to forage and re-taken into the mouth at any sign of danger. In this species the free larvae enter the mouth at roughly 0.5 in standard length, the same early stage described for its sister species Satanoperca curupira. Specific clutch counts for Satanoperca setepele were not published in the description, but jurupari-group eartheaters are moderately fecund mouthbrooders, typically carrying broods on the order of one to two hundred larvae — fewer eggs than an open substrate-spawner of similar size, the trade-off for the heavy protection that buccal incubation provides. Spawning is keyed to the warm season (October to January in the wild), and as with related Satanoperca the parents share brood care, with both sexes capable of holding larvae.
In the aquarium
Satanoperca setepele is only thinly represented in the hobby. Described in 2021, it reached aquarists chiefly as wild imports labelled 'Tocantins jurupari' or simply mixed in with other jurupari-group eartheaters, and dedicated keeping accounts remain scarce — the Cichlid Room Companion profile, for instance, is built around a single male kept by Lee Newman in Canada. Husbandry therefore follows the well-trodden requirements of the jurupari group rather than a body of species-specific experience. These are sand-sifting fish, so a deep bed of fine, smooth silica sand is essential: it lets the fish express its natural feeding behaviour and protects the delicate gill rakers it sieves with, whereas gravel will be endlessly rearranged and can abrade the gills. Give a group a long tank — on the order of 59 in and around 90–105 US gal for a small group — with an open sandy foreground for grazing, some driftwood and leaf litter for cover, and gentle, well-oxygenated flow. As a smaller eartheater (under about 6 in SL) it is less demanding on space than the larger Satanoperca, but it is still best kept in a group of five or more, since these fish are loosely social and a single pair can become a target of bullying. Water should mirror the warm, soft, clearwater Tocantins-Araguaia floodplain: temperature around 79–84 °F, pH on the acidic to neutral side (roughly 5.5–7.0), and modest hardness, with the very clean water and steady maintenance that all eartheaters demand — they are notably sensitive to accumulated nitrogenous waste and prone to head-and-lateral-line erosion when neglected, so generous filtration and large regular water changes are the rule. Feeding is straightforward: a varied diet of small live and frozen invertebrates (bloodworm, daphnia, brine shrimp), good-quality sinking pellets and the occasional vegetable supplement keeps them in colour, ideally offered as sinking food they can hunt out of the sand. Tankmates should be peaceful, similarly warm-water South Americans that will not out-compete a deliberate bottom-feeder at mealtimes — other calm geophagines, larger characins and headstanders that swim higher in the column, and similarly sized non-aggressive cichlids. Aggression is mild outside of breeding; the main pitfalls are coarse substrate, dirty water, and keeping too few fish.
Conservation
Satanoperca setepele has not been formally assessed by the IUCN Red List and currently carries no Red List category (Not Evaluated). In the original description the authors offered their own informal judgement that, given the species' wide spread across the Rio Tocantins basin and the absence of any detected specific threat, its extinction risk appears low and it would qualify as Least Concern under IUCN criteria — but that is the describers' recommendation, not an official assessment, and the species has no CITES listing either. The wider context is the Tocantins-Araguaia basin itself, which is among the most heavily dammed river systems in the Amazon region: the Serra da Mesa, Lajeado, Estreito and other large hydroelectric reservoirs have fragmented the Tocantins, altered its natural flood pulse, and converted long stretches of flowing clearwater river into still impoundments. A floodplain, lagoon-dwelling, sedentary fish like Satanoperca setepele is exactly the kind of species whose habitat is reshaped by such changes, and the establishment of an introduced population in the distant upper Rio Paraná is itself a reminder of how readily the basin's fauna is now being moved around. None of these pressures is documented as a present danger to the species, but they are the backdrop against which any future assessment of it should be read.