Taxonomy & naming
Aequidens pirilampo was described in 2024 by Renata C. D. Oliveira, Luiz F. C. Tencatt, Gabriel D. C. Deprá, Ricardo Britzke, Cláudio Oliveira and Weferson J. da Graça, in Neotropical Ichthyology (volume 22), in a paper titled 'A new species of Aequidens (Cichliformes: Cichlidae) from the rio Paraguai basin, Brazil.' The genus itself is much older: Eigenmann and Bray raised Aequidens in 1894 — at first as a subgenus of Astronotus — for medium-sized South American 'acaras' with even-sized teeth, the name meaning 'equal teeth.' It long served as a sprawling catch-all, and many of its former members have since been moved to genera such as Andinoacara, Bujurquina, Laetacara, Krobia and Cleithracara. What remains sits in the subfamily Cichlinae, tribe Cichlasomatini. The describers placed Aequidens pirilampo nearest Aequidens plagiozonatus, the only other congener whose dark flank bars run anteriorly oblique rather than vertical; the two differ in head profile, jaw proportions, the pattern of the lateral band, and the count and form of the eight flank bars (numbered 1a, 1p and 2–7). The epithet pirilampo, Portuguese for 'firefly,' is a noun in apposition, chosen because the iridescent green of living fish recalls the light of the bioluminescent beetles common where the species occurs. The holotype is catalogued in the Nupélia collection at the Universidade Estadual de Maringá, and the type series was taken from tributaries of the upper Rio Correntes.
Morphology
Aequidens pirilampo is a small acara, reaching about 3.5 in standard length (FishBase). The body is fusiform and moderately compressed, in the usual Aequidens mould, with 14–15 dorsal-fin spines and 9–11 soft rays. Its diagnostic features are what set it apart. Eight dark-brown flank bars run anteriorly oblique rather than vertical — a trait it shares only with Aequidens plagiozonatus. The dorsal head profile is almost straight from the snout-tip to the back of the eye, then broken by a conspicuous concavity over the interorbital region, and a round spot marks the midflank. In preserved fish the lateral band is discontinuous, broken into blotches that show most clearly where they meet the flank bars. The describers also list a run of negative characters that separate it from relatives: no iridescent vermiculations on the cheek and opercle, no large dark blotches on the cheek, and no preopercular spot. The living animal is the source of the name — an iridescent green sheen over the body, likened to a firefly's glow, that fades once a specimen is preserved. As is usual for a recently described acara, notes on sexual dimorphism remain limited.
Habitat
The species is endemic to the headwaters of the Rio Correntes, a tributary within the Rio Paraguai basin in the Cerrado biome of Mato Grosso, Brazil — a high, seasonally dry savanna plateau. That home makes it a genuine rarity among Aequidens, most of which are Amazon and Orinoco fishes; Aequidens pirilampo belongs instead to the upper Paraguai and La Plata watershed. It is confined to the upper Rio Correntes above a large waterfall, where it is the only cichlid present — a classic isolated headwater fauna, cut off from the richer communities downstream. The describers and FishBase record a distinctive setting: lentic, or still-water, mesohabitats of extraordinarily crystalline water with submerged vegetation, at depths ranging from about 4 in, where hatchlings shelter, to a little over a metre. These clear, plant-fringed Cerrado pools are as fragile as they are distinctive, and the type-series localities (around 17°32′S 54°25′W) lie in the cooler, higher reaches of the basin rather than in tropical lowland river.
Feeding
No dedicated dietary study has been published for Aequidens pirilampo, but its biology and the ecology of the genus point to a small benthic omnivore. Aequidens generally forage over the substrate for aquatic insect larvae, micro-crustaceans and other small invertebrates, and take detritus, algae and plant material as well. FishBase places Aequidens pirilampo at an estimated trophic level of about 3.2, derived from its size and the trophic ecology of close relatives. Living in clear, vegetated, still-water headwater pools, it is well placed to glean small invertebrates from the plants and bottom and to pick at substrate detritus — the generalist acara strategy rather than any specialised feeding mode.
Mating
No courtship behaviour has yet been described for Aequidens pirilampo, but Aequidens are well known as monogamous, pair-bonding, biparental substrate spawners, and the species is expected to follow suit. Pairs form and defend a shared territory, clean a spawning surface — a flat stone, a leaf, or a firm patch of substrate — and court with lateral displays, fin-spreading and heightened coloration. In the clear, structured, still-water pools it inhabits, with hatchlings recorded sheltering in the shallowest margins, the fish fits the familiar acara picture: attentive parents raising a guarded brood within a defended patch of a quiet pool. As with many acaras, the sexes are likely broadly similar outside breeding, separated only by subtle differences in size and finnage.
Breeding
There is no published account of spawning, clutch size or fry development specific to Aequidens pirilampo. By the consistent biology of the genus, it is an open, biparental substrate spawner: adhesive eggs are laid on a cleaned firm surface and tended by both parents, the female fanning and guarding the clutch while the male defends the territory. After hatching, the larvae are moved to pits, and the free-swimming fry are herded and protected as a school by both adults. The record of hatchlings occupying the shallowest, roughly 10-cm-deep margins of the clear pools fits this kind of careful biparental brood-rearing in sheltered water. Many Aequidens breed reliably in aquaria on exactly this template, but for Aequidens pirilampo the specifics remain to be documented — what is stated here is inferred from the genus, not recorded for the species.
In the aquarium
As of its 2024 description, Aequidens pirilampo is not established in the aquarium hobby. It is a newly named endemic from a remote Cerrado headwater, with no body of keeping experience, no trade name, and no breeding history of its own. Treat every husbandry note here as extrapolation from the genus and the species' known habitat, not as recorded fact.
Aequidens as a group are popular, manageable medium-small cichlids — generally peaceful for their size outside breeding, hardy, and undemanding once water quality is good. Tank: a fish under 4 in would suit a planted aquarium with open swimming space, a soft substrate and gentle structure rather than a bare or boisterous setup. Water: its natural home is exceptionally clear, vegetated, still water, which argues for clean, well-filtered, soft-to-neutral water and a well-planted aquascape. Diet: a varied omnivore mix of small frozen and live invertebrates, quality flake or micro-pellets, and some plant matter. Tankmates: were the fish ever to enter the hobby, peaceful and similarly sized companions. The honest verdict is that this is an attractive, iridescent little acara of real aquarium potential but, for now, essentially no aquarium track record — a fish to watch rather than one to source.
Conservation
Aequidens pirilampo has not been evaluated by the IUCN and carries no Red List status, consistent with its 2024 description. Its conservation interest is still easy to state: it is a single-river endemic, restricted to the upper Rio Correntes above a waterfall, where it is the only cichlid — a narrow-range, isolated-headwater fish. Such species are inherently vulnerable, because any degradation of that one short stretch of habitat affects the entire known population. The upper Paraguai Cerrado faces the familiar regional pressures of agricultural expansion, water abstraction, and changes to the clear-water springs and headwater pools these fish depend on — and the crystalline, vegetated water the species requires is exactly the kind most sensitive to siltation and nutrient input. No formal assessment, CITES listing or fishery interest applies, but a tiny range paired with a demanding clear-water habitat makes Aequidens pirilampo a reasonable candidate for future conservation attention.