Taxonomy & naming
Teleocichla preta was described in 2016 by Henrique R. Varella, Jansen Zuanon, Sven O. Kullander and Hernán López-Fernández in the Journal of Fish Biology (89(3): 1551-1569), on material from the Rio Xingu basin of Pará State, Brazil. The genus Teleocichla itself had been erected by Kullander in 1988 for a suite of six small rheophilic cichlids of the Xingu, Tapajós and Tocantins rapids, allied to the pike cichlids (Crenicichla) within the eartheater tribe Geophagini but convergent in body form with the African rapids cichlids of Teleogramma. Teleocichla preta was the ninth species added to the genus and, by some margin, the largest. Long known before it was named, the fish appears in the earlier literature and trade under a string of provisional labels: it is the "Teleocichla" diagnosed and illustrated by Zuanon (1999), the Teleocichla sp. "Xingu II" or "Schwärzel" (Black) of Stawikowski & Werner (2004), the form sometimes called Teleocichla sp. "Xingu IV" by importers, and the Teleocichla sp. preta of Arbour & López-Fernández (2013, 2014), who folded it into biomechanical analyses of the Crenicichla clade. The describers chose the established hobby and field name as the formal epithet. No synonyms exist, the name being newly coined; the holotype and an extensive type series are housed in Brazilian and international collections, with the type locality at the Volta Grande do Xingu near Altamira.
Morphology
Teleocichla preta has the elongate, cylindrical, goby- or worm-like body shared by the whole genus, an outline that suits a fish that lives wedged among current-scoured rocks rather than swimming in open water. It is the giant of the genus: the original description records a maximum of 5 in (about 5 in) standard length, against fewer than 3.5 in in every other Teleocichla, and in total length the fish reaches roughly 6 in. The long dorsal fin carries 21-23 spines and the anal fin 3 spines, the latter separating it from Teleocichla centrarchus and Teleocichla wajapi, which have four. The species is defined above all by colour: live adults are a uniform blackish, fading to dark brown in preservative, and this dark wash masks the faint vertical bars or zig-zag row of blotches visible on paler congeners. Freshly caught full-grown fish are described as pitch-black both in the net and in their native rapids. Beyond colour, Teleocichla preta is set apart by a deeper body (depth 17.9-21.6 % of standard length) and a notably deep, laterally compressed caudal peduncle, together with a stout lower pharyngeal tooth plate bearing molariform (rounded, crushing) teeth across its centre rather than the conical teeth of its relatives. Unlike the sexually dimorphic males of Teleocichla cinderella, males of this species do not develop drawn-out filamentous dorsal-fin rays. Sexual differences are otherwise subtle: importers of mature fish (3–4 in) have reported that some individuals carry a deep-black longitudinal band in the dorsal fin while others lack it, and on body shape the banded fish were tentatively taken to be females, though the cue is not yet confirmed.
Habitat
The species is restricted to the Rio Xingu drainage in Pará, eastern Brazilian Amazonia, and falls entirely within the Xingu freshwater ecoregion. It is known from the Rio Xingu between Cachoeira Chadasinho, upstream of São Félix do Xingu, and Cachoeira do Jericoá at the Volta Grande do Xingu downstream of Altamira, and from the lower reaches of the Rio Iriri, the Xingu's largest tributary. Throughout this range it is a true rapids specialist, collected in moderate-to-fast, shallow rapids of clear water over a bed of large rocks with little accumulated sediment. Snorkelling observers (Zuanon and Varella) watched individuals make short sorties from their rocky hideouts, moving alone among small stones and through crevices in the larger boulders before retreating. This is shoreline and channel-margin habitat in the shallow band, generally only about a metre or so deep, where the current is strongest and the substrate cleanest. The Xingu is a classic clearwater river: measurements from the rapids at Altamira give roughly pH 6.5, very soft water (around 1 °dH general and below 1 °dH carbonate hardness, conductivity near 120 µS/cm), and warm temperatures that climb to about 90 °F during the low-water season. Teleocichla preta is therefore a fish of soft, warm, well-oxygenated, fast clearwater, and like all Teleocichla it carries a greatly reduced swim bladder, so it sinks the instant it stops swimming and relies on perching and clinging to the rock rather than holding station in midwater.
Feeding
Teleocichla are not the large-mouthed ambush predators that many of their Crenicichla relatives are; their modest gapes are built for picking small animals off the substrate, and Teleocichla preta is a benthic invertivore that works the rock surfaces and crevices of the rapids. What makes it distinctive is durophagy, the crushing of hard-shelled prey. Its stout lower pharyngeal plate, paved with molariform teeth, lets it process armoured food that its conical-toothed congeners cannot, and the gut of Teleocichla preta is dominated by exactly such items: the cases of caddisfly larvae (Trichoptera) together with snails (gastropods) and bivalves, supplemented by softer midge larvae (Diptera: Chironomidae) and mayfly nymphs (Ephemeroptera). FishBase places it around trophic level 3.3. In the densely packed rapids community of the Xingu, where several Teleocichla and many other endemic fishes partition the same rocks, this crushing specialization on shelled invertebrates is most plausibly read as a way of exploiting a food resource that the genus's many small-mouthed, soft-prey pickers leave largely untouched.
Mating
The courtship and pair-forming behaviour of Teleocichla preta has not been formally documented in the wild, and what can be said is drawn from the genus and from the first aquarium imports. Teleocichla are substrate-bound fish whose social life centres on small territories anchored to a particular stone, pit or rock cavity; adult males of several species are territorial and guard such shelters, ducking under flat rocks when threatened. Within that template Teleocichla preta appears to be at the peaceable end of the spectrum. A group of sexually mature wild-caught adults proved "extremely peaceful among themselves" in captivity, with no serious aggression observed, which suggests that pairing is not the violent, high-stakes affair it can be in some rapids cichlids. The candidate sexual signal noted in those fish, a black longitudinal band in the dorsal fin of presumed females, may turn out to play a role in pair recognition or readiness, but this remains an open question. As in other Teleocichla, behavioural rather than spatial barriers seem to keep the several closely related, co-occurring species reproductively separate, since they share the same rocks.
Breeding
No detailed account of spawning in Teleocichla preta has been published, and the species had scarcely been kept until recently, so its reproduction is described here from the consistent pattern of the genus. Teleocichla are cave or crevice substrate-spawners with biparental care: a pair selects a sheltered cavity beneath or within the rocks, the female attaches a modest clutch of eggs to a hidden surface, and both parents tend the eggs and guard the resulting fry. Congeners have been bred in Europe, confirming this nuclear-family, cave-brooding strategy, though clutch sizes for the genus are small and have not been precisely tabulated for most species; figures on the order of a few dozen to perhaps a hundred eggs are typical of small rheophilic cichlids of this kind, and the protected crevice nest shelters the brood from the strong current and from the crowd of substrate-foraging neighbours. The triggers and developmental timetable specific to Teleocichla preta remain undocumented. Given the warm, soft, fast clearwater of its home rapids, successful spawning is likely to demand strong flow, high oxygen, scrupulously clean water and a choice of tight rock caves, the conditions under which the genus reproduces.
In the aquarium
Teleocichla preta has only intermittently reached aquarists and remains a specialist's fish rather than a hobby staple. The obstacles begin at the source: rapids Teleocichla are difficult to net, ship notoriously poorly, and historically arrived in tiny numbers at high prices, with importers who would not guarantee live delivery. The fish are also intolerant of being kept in still, low-oxygen water, the conditions that kill freshly imported rheophiles. Anyone keeping the species must therefore reproduce its rapids habitat closely. That means a long tank floored with smooth rounded stones and stacked rockwork that creates abundant caves and crevices, brisk water movement from a powerful pump or powerheads, very high oxygenation, and a mature, lightly stocked filtration system delivering clean, stable, soft water. Target parameters mirror the Xingu: warm (about 79–88 °F), acidic to near-neutral (pH roughly 6.0-7.5) and soft, with the strong current the fish is built to live in. Because the swim bladder is reduced, these are bottom-oriented fish that perch on and dart between rocks; open swimming space matters far less than secure hiding places. Diet should lean on meaty, invertebrate fare, frozen and live bloodworm, daphnia, and small crustaceans, in keeping with a crushing invertivore, and most specimens learn to take quality frozen and prepared foods. On temperament, the species is encouraging: the imported group of adults was strikingly peaceful with one another, so a small group in a large, rock-rich, fast-flowing tank is a reasonable goal, alongside other robust, current-tolerant Xingu species rather than slow or delicate fish. The honest summary is that this is a rewarding but demanding rheophile, best left to keepers who can guarantee strong flow, pristine water and a properly built rockscape; it is not a beginner's cichlid, and it has not yet become established in the hobby.
Conservation
Teleocichla preta has not been evaluated for the IUCN Red List (status Not Evaluated), and it carries no CITES listing. That absence of a formal assessment should not be read as reassurance. The species is a narrow-range endemic confined to the rapids of the Rio Xingu and lower Rio Iriri, and that habitat is among the most heavily altered stretches of river in the Amazon. The type locality lies in the Volta Grande do Xingu, the "Big Bend" that has been directly engineered by the Belo Monte hydroelectric complex, one of the largest dam projects on Earth, which diverts the bulk of the river's flow away from the rapids and floods or dewaters the very habitats this fish depends on. Commentators noted at the time of the species' description that the Xingu rapids hold dozens of narrowly endemic fishes likely to be devastated by the development, and broader studies of the Xingu's rapids-dwelling fish community have flagged exactly this collision between extreme local endemism and large-scale hydroelectric alteration. For a rheophilic, rock-bound specialist that cannot persist in slack or sediment-laden water, the loss or transformation of fast, clean, rocky rapids is an existential rather than a marginal threat, and Teleocichla preta is a clear candidate for future conservation concern even though no formal category has yet been assigned.