Taxonomy & naming
Anablepsoides lungi was described by H. O. Berkenkamp in 1984, based on specimens from northeastern South America. Berkenkamp placed the species in the genus Rivulus — the catch-all genus that for most of the twentieth century accommodated the South and Central American rivulines — and it was widely known as Rivulus lungi for several decades. The current valid combination, Anablepsoides lungi (Berkenkamp, 1984), follows the generic revision that redistributed the former Rivulus sensu lato among a suite of resurrected and newly erected genera on the basis of molecular phylogenetics; the authority appears in parentheses because the species was originally described under a different genus name. The World Register of Marine Species (WoRMS) confirms the valid name as Anablepsoides lungi (Berkenkamp, 1984).
Eschmeyer's Catalog of Fishes (CAS) places the species in the family Rivulidae within the order Cyprinodontiformes. The genus Anablepsoides draws its name from a superficial resemblance of some members' eye morphology to the four-eyed fish Anableps, though this is an anatomical parallel rather than a functional one. The specific epithet lungi honours an individual — a surname reference in the tradition of nineteenth- and twentieth-century ichthyological description — though the identity of the honoree is not elaborated in the accessible literature.
Morphology
Anablepsoides lungi is a slender, moderately compressed rivuline reaching a maximum of approximately 3 in standard length (FishBase) — somewhat larger than many of its congeners. The body plan conforms to the non-annual rivuline pattern: an elongate, laterally compressed profile with the dorsal fin positioned well back, approximately above or slightly anterior to the anal fin, a rounded caudal fin, and the slightly upturned mouth typical of near-surface feeders. The lateral line is incomplete, as in other rivulids, represented by a series of embedded neuromasts rather than a continuous open-pored canal.
Meristic data from It Rains Fishes give 8 dorsal-fin rays, 14 anal-fin rays, and approximately 39 lateral scale counts — proportions consistent with other members of the genus. Sexual dimorphism is pronounced: males develop the iridescent metallic colouration characteristic of the genus, typically showing blue-green or teal flanks with red or reddish-orange spotting arranged in rows or scattered across the body; females are drabber, brownish or olive, and frequently carry the caudal ocellus — a dark spot at the dorsal margin of the caudal peduncle — that is common in female rivulines and is thought to function as a deflection or mimicry signal.
Habitat
The native range of Anablepsoides lungi spans the coastal lowlands of French Guiana and Suriname — two countries that together make up the northeastern margin of South America, a region characterised by broad, flat coastal plains backed by the Guiana Shield highlands. Within this zone, FishBase records the species from permanent flooded savannas and coastal swamps: shallow, still or very slow-moving water bodies subject to seasonal inundation but persisting as standing water year-round. This habitat type is distinct from the fast-flowing hill streams occupied by some congeners such as A. amphoreus, and from the Amazonian blackwater pools associated with other South American rivulines.
Water chemistry parameters reported by FishBase include a temperature around 79 °F and pH near 6 — mildly acidic conditions consistent with the tannin-stained, poorly buffered coastal plain waters of the Guianas, though not the extreme acidity of true Amazonian blackwater. The species is classed as a freshwater, non-migratory, benthopelagic fish, spending its time at or near the water surface and in the mid-water column among emergent vegetation, floating plants, and root masses that characterise the flooded savanna and swamp margins it favours.
Feeding
Like other non-annual rivulines of comparable size, Anablepsoides lungi is a carnivore that targets small invertebrates at and near the water surface. In the flooded savannas and coastal swamps it inhabits, the natural diet is likely dominated by small insects — including adult and larval dipterans, small beetles, and other invertebrates associated with still-water margins — together with microcrustaceans and zooplankton-sized prey available in the water column. The upturned mouth is well-suited to intercepting prey at or just below the surface film.
In captivity the species accepts the full range of small live and frozen invertebrate foods without difficulty: fruit flies (Drosophila), small waxworms, mosquito larvae, Daphnia, cyclops, Artemia nauplii, and frozen bloodworm all serve well. Fry are started on Artemia nauplii from the first days of free swimming. As with most killifish, varied feeding with suitably sized live and frozen items maintains the best condition and colouration.
Mating
Anablepsoides lungi is a non-annual killifish: it lives in permanent or near-permanent water and produces eggs that are incubated in water rather than buried in substrate to survive desiccation. Its reproductive mode is that of a plant or mop spawner — the pair deposit individual adhesive eggs on fine-leaved aquatic vegetation, floating plants, root masses, or the fibres of an artificial floating spawning mop over a sustained period of days or weeks. This mode differs fundamentally from the peat-spawning annual killifish with which the family is sometimes stereotyped.
Breeding accounts from It Rains Fishes describe males as potentially aggressive toward one another and toward females outside active spawning; in confined quarters a male may persistently harass a female. In aquarium settings a single pair or a group with excess females is a more practical arrangement than multiple males. Males court with lateral displays that expose the full iridescent body colouration, positioning alongside the female before the pair press together to deposit an egg on a chosen surface.
Breeding
Spawning in Anablepsoides lungi is extended rather than event-based: conditioned pairs produce approximately 5–15 adhesive eggs per day over sustained periods, making total production modest but consistent. The eggs are amber-coloured and approximately 0.5 in in diameter — relatively large compared with the annual killifish, which reflects the direct-development strategy of non-annual rivulines. Eggs incubate submerged in water at around 79 °F with no diapause, hatching after approximately 14 days. This contrasts sharply with the months-long dry incubation of annual peat-spawners.
Fry are free-swimming immediately upon hatching and accept Artemia nauplii as a first food from day one — a practical advantage over some other killifish families. It Rains Fishes notes a lifespan of up to three years under good aquarium conditions, consistent with the relatively large size and non-annual life history strategy. Sexual maturity is reached at around five months (FishBase). Eggs and fry should be separated from adults if possible, as the parents will consume both. Incubating eggs in a small container with a drop of methylene blue helps prevent fungal losses.
In the aquarium
Anablepsoides lungi is a rewarding killifish for an intermediate keeper: more accessible than the annual soil-spawners, comparatively long-lived, and colourful when adult males are in condition. It does best in a small, well-planted species or near-species aquarium with soft, slightly acidic water (pH 5.5–6.5, temperature 75–81 °F) and dense surface vegetation or floating plants that replicate its natural swamp-margin habitat. A tight-fitting lid is essential — rivulines are accomplished jumpers and will escape through the smallest gap.
Male aggression toward conspecifics and toward females outside spawning periods makes tank management important. A single pair, or a group of one male and two or three females, avoids the worst of the inter-male conflict and distributes female harassment. Tank decor should provide visual breaks — Java moss, Ceratophyllum, Indian fern, or similar fine-leaved plants — and floating spawning mops for egg deposition. Because the species is not widely traded commercially, it is mainly found through killifish society membership and among dedicated rivuline hobbyists who maintain breeding lines. It Rains Fishes notes the species is an excellent jumper, reinforcing the need for a securely covered aquarium at all times.
Conservation
The IUCN assesses Anablepsoides lungi as Least Concern, a status consistent with a range spanning two countries (French Guiana and Suriname) and encompassing multiple coastal drainage systems. The flooded savannas and coastal swamps of the Guiana coast are not among the most severely deforested or degraded freshwater habitats in South America, and no population-level declines are documented for this species in the accessible literature.
Nonetheless, the lowland coastal habitats of the Guianas face incremental pressure from agricultural expansion — particularly rice and sugarcane cultivation on the coastal plain — drainage schemes, and coastal infrastructure development. The introduced mosquitofish (Gambusia) has established itself across much of tropical South America and poses competition and predation pressure on small-bodied surface-dwelling killifish wherever it overlaps. Like most small, morphologically similar rivulines from the Guianas, A. lungi is only occasionally encountered in the ornamental fish trade, meaning that hobbyist populations in killifish societies represent a meaningful secondary repository for the species outside its natural range.