Taxonomy & naming
Hemeraia chicha was described in 2012 by Henrique R. Varella, Sven O. Kullander and Flávio C. T. Lima in the journal Neotropical Ichthyology (vol. 10, no. 2, pp. 233–244), on material collected during recent surveys of the rio Juruena, a major headwater of the rio Tapajós in Mato Grosso, Brazil. The holotype (MZUSP 109198, 4 in SL) was taken in the rio Papagaio about 2 mi above the Sapezal–Tangará da Serra road, with an extensive paratype series from the Papagaio drainage held at the São Paulo (MZUSP), Porto Alegre (MCP), Stockholm (NRM), Philadelphia (ANSP), Campinas (ZUEC) and Maringá (NUP) collections. Crenicichla is the most species-rich genus of South American cichlids — well over eighty valid species at the time of description — and the authors could not place chicha in any of the established species groups (saxatilis, reticulata, lugubris, wallacii, missioneira). Its diagnostic combination is unusual: the third and fourth infraorbital bones are co-ossified (fused) rather than separate, the preopercular margin is smooth rather than serrated, microbranchiospines are absent, and there are 66–75 scales in the E1 longitudinal row. The fused infraorbitals and smooth preopercle are shared, within the whole genus, only with Crenicichla hemera Kullander, 1990 of the adjacent rio Aripuanã (rio Madeira basin), and the two are interpreted as putative sister species — a pairing across two adjoining Brazilian-Shield drainages. In the same paper the authors confirmed that Crenicichla guentheri Ploeg, 1991 is a junior synonym of Crenicichla hemera. Hemeraia chicha itself has no synonyms; the genus was erected by Johann Jakob Heckel in 1840.
Morphology
Hemeraia chicha is an elongate, laterally compressed, medium-small pike cichlid — laterally flattened rather than cylindrical and robust like the larger reticulata-group pikes. The largest specimen in the type series was a male of 5.5 in standard length (SL); the largest female measured 4 in SL, and FishBase rounds the maximum to about 5.5 in SL. The head is slightly deeper than wide with a moderately long, bluntly pointed snout and a slightly prognathous lower jaw; the jaws carry an outer row of about fifty fixed, pointed, slightly recurved teeth backed by several inner rows. Diagnostic markings include conspicuous black preorbital and postorbital stripes and a distinctive narrow suborbital stripe running obliquely down and back from the third infraorbital toward the preopercular margin — the feature that most readily separates it from the faint, rounded suborbital marking of Crenicichla hemera. A dark midlateral stripe runs from the shoulder to the caudal peduncle and merges with seven to nine faded vertical bars to give a marbled pattern; there is no distinct humeral blotch. An ocellated black caudal blotch, ringed with light pigment, sits high on the upper part of the tail base. In life, young fish are yellowish-green above with small scattered orange flank spots, red-margined fins and a white-ocellated caudal spot. Mature males are the showpiece: head, nape and forward dorsum turn lemon-green, the flanks are bluish-grey overlaid with irregular wavy orange vertical stripes that condense into a net-like pattern toward the tail, and the dorsal and caudal fins flush red. Sexual dimorphism is otherwise modest — the soft dorsal-fin rays (roughly the 6th–12th) are elongated in mature males, reaching to the middle of the caudal fin or beyond, while ripe females are rounder-bodied.
Habitat
The species is known only from the rio Papagaio and its tributaries — including the rio Sacre, rio Verde and the ribeirão Vinte e Cinco de Maio — within the rio Juruena system, the upper rio Tapajós basin of the state of Mato Grosso, Brazil. This is Brazilian-Shield drainage: the Papagaio runs transparent (clearwater) over a predominantly rocky bed with swift current and numerous rapids. One of the describers (Lima), snorkelling the river, found Hemeraia chicha mainly in backwaters and in the slacker water behind large boulders rather than out in the fastest flow, and also took it in smaller, slightly turbid tributaries with sandy-muddy bottoms. The fish was the only Crenicichla present above the Cachoeira do Utiariti — a waterfall roughly 295 ft high on the rio Papagaio — and occurred both above and below it; below the falls it lives alongside an undescribed pike of the Crenicichla saxatilis group. As a shield-river rapids fish its parallels Crenicichla hemera, which similarly straddles a tall waterfall on the neighbouring rio Aripuanã. Specific in-situ chemistry was not published in the description, but waters of this type on the central-Brazilian plateau are soft and warm; FishBase classes the species as a tropical freshwater, benthopelagic fish. Recorded depths are not published, but as a fish of shallow rapids, boulder margins and small tributaries it occupies the upper few metres of the water column.
Feeding
No gut-content study of Hemeraia chicha has been published, but its anatomy and its membership in the genus place it firmly among the pike cichlids — elongate, large-mouthed ambush predators. The jaws are armed with an outer row of around fifty fixed conical teeth and several inner rows of inclinable teeth, the classic gripping dentition of a fish that seizes mobile prey. FishBase estimates a trophic level of about 3.2, consistent with a carnivore that takes small fishes together with aquatic insect larvae, crustaceans and other invertebrates picked from the rocky substrate and from the slacker water behind boulders where it lurks. In its rapids habitat it functions as a small mid-level predator, hunting from cover in the manner typical of the smaller, rheophilic members of the genus rather than as a bottom-clamped specialist like the related rapids genus Teleocichla.
Mating
The courtship and pair behaviour of Hemeraia chicha have not been documented in the wild or in captivity. The genus as a whole is monogamous: pike cichlids form lasting pair bonds, with both partners defending a territory before and during spawning, and the smaller, rheophilic species of the genus typically pair off within the cover of rock and crevice. The description records no pronounced sexual dimorphism in Hemeraia chicha beyond the elongated soft dorsal rays of mature males and the rounder abdomen of ripe females, so — as in many pikes — sexing outside of breeding condition is difficult and pair formation is best achieved by raising a group and letting a compatible pair settle. The fish is noted as inquisitive, readily approaching snorkelling divers, which is consistent with the bold, curious temperament reported across the genus.
Breeding
Breeding has not been documented for Hemeraia chicha, either in the wild or in the aquarium, and the original description carries no reproductive data. Inference must therefore rest on the genus, which is consistent and well known: Crenicichla are biparental cave or crevice spawners. The female typically attaches her eggs to the roof or wall of a sheltered cavity — a rock crevice, undercut or, in captivity, a cave or length of pipe — and both parents guard the clutch and the resulting fry, the female tending the eggs while the male patrols the territory. Egg numbers in the smaller, dwarf-to-medium pikes commonly run from a few dozen to a few hundred; in the absence of any published count for chicha a genus-typical figure of roughly 50–300 eggs is the best available estimate. Larvae are guarded as a school and retreat to cover when threatened. For a rapids fish of this size, soft warm water and a secure cave are the expected requirements, but the specifics for this species remain unrecorded.
In the aquarium
Hemeraia chicha is a rarity in the hobby. It has occasionally reached aquarists as wild-caught by-catch from the rio Papagaio, exported alongside the region's prized tetras under Brazil's more open ornamental-export rules, and it is prized precisely because it is so seldom available. There is no established body of captive husbandry for the species, so any keeping advice is extrapolated from its wild habitat and from experience with similar small rheophilic pikes.
This is a clearwater rapids fish from a soft, warm, fast-flowing river, and a tank should reflect that. A medium-small pike of around 5.5 in does not need a giant aquarium — a footprint of roughly 47 in (about 55 US gal) suits a pair — but it does want strong, well-oxygenated flow from a powerhead or an oversized canister return, scrupulously clean water, and a rocky aquascape of piled stone and cobble that provides both current breaks and the caves and crevices the fish uses for shelter and, potentially, spawning. A sand or fine-gravel base with scattered boulders mimics the Papagaio bed. Subdued lighting and some driftwood help settle a naturally wary, inquisitive fish.
Water should be soft and warm: aim for roughly 79–86 °F and a pH on the acidic-to-neutral side (about 5.5–7.0), with low mineral content, mirroring the transparent shield-river water it comes from. As a predator it will take live and frozen meaty foods — chopped fish and shrimp, earthworms, larger frozen invertebrates — and most specimens can be weaned onto quality sinking carnivore pellets. Tankmates should be chosen with the fish's predatory nature in mind: anything small enough to be swallowed is prey, so companions should be robust, similarly-sized, current-tolerant species (larger tetras and other characins, loricariid catfishes) rather than small or slow fish. Like most pikes it can be territorial, especially a settled pair, so give it space and sightline breaks. Because the species is wild-collected and essentially undocumented in captivity, it is best regarded as a fish for the experienced keeper who can provide pristine, flowing, soft water and is prepared to work out its needs first-hand.
Conservation
The IUCN Red List assesses Hemeraia chicha as Least Concern (assessed 7 November 2018 by the Instituto Chico Mendes de Conservação da Biodiversidade, ICMBio; published 2022), with the population trend listed as unknown and the range given as Brazil. The species carries no CITES or CMS listing. Although the Least Concern category reflects no documented decline, chicha is a narrow-range endemic — confined to the rio Papagaio system in the upper Tapajós — and narrow-range shield-river fishes are inherently vulnerable to localized habitat change. The upper Tapajós and Juruena basin lies within Brazil's agricultural-frontier plateau around Sapezal and Campo Novo do Parecis, where deforestation for soy and other row crops, and the small hydropower schemes that proliferate on clearwater shield rivers, are recognised regional pressures on stream fishes; the broader Tapajós basin has also been the focus of major dam-development proposals. None of these is documented as a present threat to this particular cichlid, but they are the backdrop against which the long-term status of a single-river endemic should be read.