Taxonomy & naming
Maratecoara lacortei was first described by Kenneth Lazara in 1991 as Cynolebias lacortei in the Journal of the American Killifish Association, volume 23(5): 141–144, on the basis of specimens collected near Aruanã (then spelled Aruana) in Goiás state, Brazil. The authority appears in parentheses — (Lazara, 1991) — because the species has since been transferred out of Cynolebias. The valid name, as recognised by Eschmeyer's Catalog of Fishes, is Maratecoara lacortei (Lazara, 1991), placing the species in the plesiolebiasine genus Maratecoara.
The genus Maratecoara was erected to accommodate a small set of annual killifishes from central Brazilian savanna drainages that share a distinct combination of morphological characters and are now resolved within the subfamily Rivulinae (family Rivulidae). A landmark taxonomic revision by Wilson J. E. M. Costa (2007, Zootaxa 1410: 1–41) treated Pituna, Plesiolebias, and Maratecoara together and provided the authoritative redescription of M. lacortei, designating the holotype as MZUSP 38805 from a temporary pool at Aruanã, road GO-173, Goiás state (14°57'0.5"S, 51°1'23.7"W, altitude 797 ft). Material examined in that revision extended the known range across the Araguaia–das Mortes basin through Goiás, Tocantins, and Mato Grosso.
Morphology
Adults reach a maximum of approximately 2 in standard length (SL), with males and females running close in total size — Costa (2007) measured the largest examined male at 1.5 in SL and the largest female at 1 in SL. Meristic counts documented for the species include approximately 11–12 dorsal fin rays, 15–16 anal fin rays, and around 25–26 lateral-line scales. The caudal fin carries 27–30 rays, a count that is diagnostically useful within the genus.
Sexual dimorphism in colour is pronounced. Males are immediately striking: the body above the level of the anal-fin base is metallic blue to purple, covered in orange spots and bars; a broad, bold orange blotch sits on the anteroventral flank immediately posterior to the pectoral fin. The iris is bright green with a vertical black bar through the pupil. The dorsal fin is metallic blue with orange rays; the anal fin transitions from pale orange basally to a vivid bright blue distal zone; and the caudal fin is metallic blue with orange stripes running parallel to the rays. Females are substantially less ornate — light brownish-grey overall with hyaline fins and a pale blue wash on the opercle.
Habitat
The native range of Maratecoara lacortei lies within the Araguaia River basin of interior Brazil, centred on the cerrado biome and its transitional zones with the southern Amazonian forest. The species is known from Goiás, Tocantins, and Mato Grosso states, occupying seasonal swamps, shallow lagoons, and temporary pools embedded within savanna grassland and gallery-forest edges.
The pools it inhabits are annual by nature: they fill with the onset of the Amazonian rainy season (roughly October–March) and progressively evaporate through the dry season until they disappear entirely. Substrate in these pools is typically soft peat, mud, and organic detritus — exactly the medium into which the fish will later bury its eggs. As noted in the It Rains Fishes account, the species now occurs not only in primary forest swamps but also in secondary forest and fully deforested savanna, suggesting some tolerance for human-altered landscapes, though the overall pool-formation dynamic remains dependent on intact seasonal hydrology. FishBase records a water temperature range of 72–79 °F for the species.
Feeding
Maratecoara lacortei is a small predator adapted to the invertebrate-rich, seasonally productive waters of the cerrado. In the wild it takes invertebrates — aquatic insect larvae, small crustaceans, and similar prey — from the water column and substrate during the brief wet-season window available to it. The life-history pressure of completing growth and reproduction within a few months selects for efficient, opportunistic feeding.
In captivity the species readily accepts a variety of live and frozen invertebrate foods. Newly hatched brine shrimp (Artemia nauplii) are an appropriate first food for fry from the moment they become free-swimming, and adults do well on a varied diet of Daphnia, bloodworm, white mosquito larvae, and similar items. Conditioning adults on high-protein live and frozen foods before and during breeding improves both egg production and egg quality.
Mating
Like all members of the South American annual killi group, Maratecoara lacortei is a soil-spawning annual whose reproductive biology is entirely shaped by the seasonal drying of its pools. Spawning takes place during the wet season while pools hold water; males court females with displays of their brilliant flanks and fins, which are among the most vivid in the Maratecoara group. Males can be aggressive toward one another and, at times, persistently toward females — hobbyists working with the species recommend maintaining one male with multiple females to distribute male attention and reduce female stress.
The pair spawns by descending to the substrate together, where they press side by side and deposit eggs singly or in small groups directly into soft peat, mud, or detritus. Eggs are buried rather than attached to vegetation or scattered freely in the water column. The eggs themselves are small — approximately 0.5 in in diameter — and encased in a tough chorion that resists desiccation as the surrounding substrate dries out over the following weeks and months.
Breeding
After the eggs are buried, the adult fish senesce and die as their seasonal pool dries out — M. lacortei, like all true annual killifishes, does not survive the dry season. The eggs enter diapause, a state of arrested development encoded in the genome of annual rivulids, which allows the embryo to survive the months-long drought in a quiescent state within the dry substrate.
Incubation in the hobby typically runs three to five months or more, depending on temperature and the timing of the re-wetting trigger. The It Rains Fishes account notes that storage at 75–82 °F is standard, while temporarily elevating temperature to 86–91 °F can shorten incubation — a technique sometimes used when a hobbyist wants to move a batch along. The practical protocol for the aquarium involves placing the spawning medium (peat moss or coco coir) into a sealed container after removal from the tank, keeping it just slightly damp (not wet), and storing it in a warm place. After the appropriate diapause period the peat is re-wetted, and fry should appear within hours to days. Fry are robust and large enough to take freshly hatched Artemia nauplii from their first day of free swimming. Growth is rapid; fish can reach sexual maturity within two to three months of hatching.
In the aquarium
Maratecoara lacortei is a manageable and rewarding annual killi for hobbyists willing to engage with the diapause cycle. A standard setup uses a small, heavily planted or dimly lit tank of 10–15 US gal for a breeding group of one male and two or three females. A tray or container of damp peat moss or fine coco coir on the tank floor provides the spawning medium; the pair will dive into it and bury eggs over the course of the wet-season simulation. Water temperature in the range of 72–79 °F and a slightly soft, slightly acidic to neutral pH suits the species well, reflecting the cerrado pool chemistry of its home drainage.
Cover is appreciated — the fish are somewhat shy outside of breeding activity — and the tank should be kept covered to prevent jumps, which are typical of the family. After six to eight weeks of spawning, the peat is removed and stored for the diapause period; a fresh tray is added or the tank is broken down and re-established. Because the adult lifespan in captivity mirrors the wild pattern and rarely exceeds twelve months, maintaining the species requires commitment to the full annual cycle: spawning, diapause storage, re-wetting, and rearing. For hobbyists who follow that cycle, the species is a reliably reproducible and visually spectacular representative of the South American annual killi group.
Conservation
FishBase reports Maratecoara lacortei as Least Concern based on IUCN data, though no dedicated primary IUCN assessment record with a taxon-specific URL was located during research for this article. The species occupies a cerrado distribution in the Araguaia River basin — a biome under severe and ongoing pressure. The cerrado has lost more than half its original extent to agricultural conversion, principally soy and cattle production; the seasonal pool systems that annual killies depend on are vulnerable to drainage, groundwater depletion, and the homogenisation of hydrology by large-scale agriculture.
Additional threats include the introduction of mosquitofish (Gambusia affinis and related species), which have been released widely in tropical South America for mosquito control and are documented predators of small fish eggs and fry. M. lacortei's restricted habitat — small, isolated temporary pools — means that local populations are ecologically fragile even if the species is not yet globally threatened. The fact that it persists in secondary forest and deforested savanna habitats offers some reassurance, but the long-term security of its pool-forming hydrology under continued cerrado clearing is uncertain. The species is maintained in killifish hobby collections worldwide, providing an ex situ buffer that has proven important for several cerrado endemics.