Taxonomy & naming
Teleocichla centrarchus was described by the Swedish ichthyologist Sven O. Kullander in 1988, in his Copeia monograph 'Teleocichla, a new genus of South American rheophilic cichlid fishes with six new species' (Copeia 1988(1): 196–230). It is the designated type species of the genus, and so the name-bearer for the whole rheophilic radiation Kullander erected in that paper. The original six species were Teleocichla centrarchus, Teleocichla gephyrogramma and T. monogramma from the Rio Xingu; Teleocichla proselytus and Teleocichla prionogenys from the Rio Tapajós near Itaituba; and Teleocichla cinderella from the Rio Tocantins near Tucuruí. The type series of Teleocichla centrarchus came from the Cachoeira von Martius (the von Martius rapids) on the upper Xingu, near the boundary between the Brazilian states of Mato Grosso and Pará — the same rapids where King Leopold III of Belgium and the ichthyologist Jean-Pierre Gosse had collected the first Teleocichla specimens in 1964, material that lay preserved in Brussels for nearly two decades until Kullander rediscovered it. Kullander coined the genus name to flag two relationships at once: 'Teleo-' nods to the African rheophilic genus Teleogramma, whose elongate, current-adapted body the South American fishes parallel through convergence, while 'cichla' signals the genuine phylogenetic affinity with the Neotropical pike cichlids of Crenicichla. The genus belongs to the New-World subfamily Cichlinae, within the crenicichline (pike-cichlid) lineage. Teleocichla centrarchus carries no synonyms; the genus has since grown well beyond its original six, with later additions including Teleocichla preta (Varella, Zuanon, Kullander & López-Fernández, 2016) and Teleocichla wajapi, bringing the described total to roughly a dozen.
Morphology
This is one of the smallest cichlids of the Amazon. FishBase gives a maximum of 2.5 in standard length (SL); the largest specimen in Kullander's type series measured 2.5 in SL, and a ripe, gravid female was recorded at just 2 in SL — under two inches and already breeding. The body is markedly elongate, slightly tapered and only moderately compressed from side to side, with a short, downturned snout and 34–37 vertebrae. The mouth is small and inferior — quite unlike the wide, predatory gape of a pike cichlid — and has been likened to the mouth of a marine dragonet (family Callionymidae), suited to picking small items off the substrate rather than seizing fish. The pelvic fins are a genus hallmark: long, relatively stiff, with the middle ray longest and a thickened outer margin, forming props the fish leans on while perched on rock. The single diagnostic feature that gives the species its name is its anal-fin spine count: Teleocichla centrarchus has four anal-fin spines, where the great majority of cichlids (and most of its congeners) have three — a trait it shares within the genus only with Teleocichla wajapi. Colour is muted and cryptic, in keeping with a life over open rock in clear water; preserved and field-photographed fish show a drab ground with faint markings. Sexual dimorphism follows the genus pattern: territorial adult males are the larger, more conspicuous fish, displaying with spread, more strongly coloured fins, while females and subordinate fish are plainer.
Habitat
Teleocichla centrarchus is a narrow endemic of the Rio Xingu drainage in the Amazon basin, recorded from the upper Xingu at the Cachoeira von Martius and through the river's rapids in the Brazilian states of Mato Grosso and Pará. This is a clearwater shield river: the Xingu drains the ancient, nutrient-poor Brazilian central highlands, and its water is transparent, very soft and slightly acidic rather than the silt-laden 'whitewater' of the Andean tributaries. Field chemistry measured at Altamira on the lower Xingu during the September low-water season ran to pH about 6.5, general hardness around 1 degree, carbonate hardness below 1 degree, iron under 0.05 mg/l, and conductivity near 120 microsiemens — strikingly dilute water. Temperatures there were warm, about 32 degrees Celsius in the main channel and reaching 35 degrees in shallow, sun-warmed margins at extreme low water. The fish live over rocky bottoms in the main river, typically in around a metre of water at low season, among and beneath the boulders and bedrock of the rapids; during the wet season the same habitat is deeper and the current far stronger. Teleocichla centrarchus is strictly rheophilic — a fish of running water, not still pools — and its reduced swim bladder, awkward hovering-then-sinking swimming style, and propping fins are all adaptations to clinging to the substrate in fast flow. Several Teleocichla species are syntopic in the Xingu, and observers have found multiple species sheltering beneath a single flat stone, so the genus partitions a crowded rocky habitat by behaviour and microsite rather than by river reach.
Feeding
Teleocichla centrarchus is a small benthic invertivore, estimated by FishBase at a trophic level near 3.1. The tiny, downturned, dragonet-like mouth is the key to its ecology: where the pike cichlids it resembles are ambush piscivores with cavernous gapes, Teleocichla cannot take large prey and instead picks small animals from the surfaces of rocks. Direct gut data for this species are scant, but observation of the genus in the Xingu suggests the fish glean small crustaceans and other invertebrates from the aufwuchs — the film of algae, detritus and micro-fauna coating the rocks — and may also snap at invertebrates drifting past on the current while peering from a crevice. Kullander interpreted the modest, picking-adapted mouth as the very trait that let Teleocichla colonise the rapids successfully: rheophily alone was not enough, since rheophilic Crenicichla exist too, but the 'callionymid mouth' opened a feeding niche that the predatory pikes could not exploit. In the rapids community it functions as one of several small rock-grazing and invertebrate-picking specialists rather than a predator.
Mating
Social structure in Teleocichla is built around male-held rock territories. Adult males defend small stones, pits or holes in the rock and retreat under flat slabs when threatened; in the genus, displaying territorial males spread and flush their fins to advertise ownership and court. The species vary in how social or aggressive they are, and Teleocichla centrarchus, with its very small adult size, is one of the more diminutive members. Field observers have found territories where a larger, brightly coloured fish (a male) shared its rock with several smaller, plainer individuals — apparently females and juveniles — hinting at a flexible, sometimes haremic arrangement rather than strict lifelong pairing. Aquarium experience with the genus bears this out: Teleocichla can be monogamous or polygamous depending on the species and circumstances, and pair or harem formation centres on a defended cavity. Because several species spawn cryptically in the same rapids, reproductive isolation among them is thought to rest on behaviour — courtship signals, coloration and timing — rather than on occupying separate habitats, since they readily share the same rocks.
Breeding
Like the rest of the genus, Teleocichla centrarchus is a cave or crevice substrate spawner: rather than excavating sand or laying eggs in the open, it deposits its clutch on the concealed surfaces of a hole or rock cranny within the male's territory and guards it there. Wild spawning has not been documented in detail for this species, but the pattern is consistent across Teleocichla and is supported by the recorded gravid female of under 2 in SL, which shows that mature fish are tiny and that breeding occurs at very small size. As a small cave-spawning cichlid, the species is genus-typically expected to produce only a modest clutch — on the order of a few dozen to perhaps a hundred eggs — with biparental or female-led brood care of the eggs and fry inside the breeding cavity. German aquarists were the first to coax Teleocichla into spawning in captivity (reported by Schliewen and Stawikowski in DATZ in 1989), confirming a cave-spawning mode under aquarium conditions, though the fish remained difficult to obtain and rear and viable fry were slow to enter the hobby. Specific egg counts, fry-development times and parental-care details for Teleocichla centrarchus itself remain essentially undocumented in the literature and are inferred here from the well-established breeding biology of the genus.
In the aquarium
Teleocichla are uncommon and demanding aquarium fish, and Teleocichla centrarchus is no exception. They have long had a reputation as hard to obtain, hard to ship and hard to keep alive: collectors find them difficult to catch among the rocks, and the fish ship poorly and tolerate a non-rheophilic environment badly — one ACA member's hard-won import of a congener arrived with most specimens already dead, and the survivors did not last. Anyone keeping the genus is therefore working with a delicate, current-loving rock specialist that has little margin for error.
The right setup is a long, low tank with a large floor area rather than a tall one, since these fish live almost entirely on the bottom. Fine sand should be strewn with stones and driftwood to create the perches, caves and sightline breaks the fish use to set up territories, and current is essential: experienced keepers run a powerhead or strong return aimed across a rock so the fish can prop themselves into the flow on their stiff pelvic and pectoral fins, which also keeps the water thoroughly oxygenated. Robust biological filtration matters, because Teleocichla are sensitive to accumulated dissolved waste — they come from extraordinarily clean, dilute water.
Water should mirror the Xingu: warm (around 28–30 degrees Celsius, and these fish tolerate the low-to-mid 30s in the wild), soft and slightly acidic, with a target pH near 6.0–7.0. Keepers commonly prepare the water with reverse osmosis to hit the very low hardness and conductivity these fish evolved in. Diet is small live and frozen invertebrates — cyclops, adult brine shrimp, glassworm, bloodworm, mosquito larvae — plus sinking, spirulina-enriched prepared foods; the fish have good appetites and are easy to overfeed. Tankmates are best chosen from the middle and upper water column to fill the levels Teleocichla ignore, and the genus is generally kept in small groups of around six to eight. Aggression is the main caution: young fish are tolerant, but mature individuals — especially breeding ones — grow territorial, and an occasional dominant adult will harry tankmates relentlessly, so plenty of broken-up rockwork and escape routes are needed. Captive breeding is rare and counts as a real achievement; it has been done in the genus but is not for the casual keeper.
Conservation
The IUCN Red List assesses Teleocichla centrarchus as Least Concern (assessment by the Instituto Chico Mendes de Conservação da Biodiversidade, ICMBio; assessed in 2018, published 2022), with a population judged stable. The assessment records the species only from Brazil, in the states of Mato Grosso and Pará — a genuinely narrow Xingu-basin range. The standout conservation issue is hydroelectric development. Part of the species' distribution falls within reaches flooded or altered by hydroelectric plants, above all the vast Belo Monte complex on the Volta Grande ('Big Bend') of the lower Xingu, which diverts most of the river's flow and has profoundly changed the rapids habitat that rheophilic cichlids depend on. The IUCN reasoning is that, because another part of the range lies within protected areas, these projects should not reduce the population enough to warrant a threatened category — hence the Least Concern listing. That conclusion deserves to be read with caution: the Xingu rapids are a centre of endemism for rheophilic fishes, dam impacts on flow-dependent species are still being measured, and the fate of a fish like the closely related Teleocichla cinderella, whose Tocantins type locality was destroyed by the Tucuruí dam, shows how quickly a narrow-range rapids endemic can lose its home to a single project. The species is not assessed as threatened today, but its long-term security is tied directly to how the regulated flow of the dammed Xingu is managed.