Taxonomy & naming
Epiplatys longiventralis was described by the Belgian ichthyologist George Albert Boulenger in 1915, based on material from swamps between Agwarba and Awka in southern Nigeria — the type locality recorded in the checklist Fauna Africana museum reference (CLOFFA). The authority appears in parentheses, indicating the species has been moved from whatever genus Boulenger originally placed it in; it is now firmly assigned to Epiplatys, a large West and Central African genus of surface-oriented panchax killifishes within the family Nothobranchiidae. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Van der Laan) is the governing name authority, and the valid combination is Epiplatys longiventralis (Boulenger, 1915).
Within the genus Epiplatys, longiventralis is part of a broad assemblage of patterned, surface-dwelling species loosely grouped as panchax killifishes. It is not a close relative of the Epiplatys chaperi or Epiplatys dageti species groups — its distribution in the Niger Delta system and lower Niger tributaries places it in a geographically distinct cluster. The American Killifish Association and the museum reference literature treat it as a valid, well-characterised species with documented populations across several river systems in the region.
Morphology
Epiplatys longiventralis is a slender, torpedo-shaped killifish reaching a maximum of approximately 2.5 in total length, with the CLOFFA reference giving 2.5 in TL and FishBase citing 2.5 in TL as the recorded maximum; the AKA reference library records 2.5 in as the upper bound. The body is laterally compressed, with the dorsal profile nearly flat and the ventral line gently curved — typical of a surface-oriented Epiplatys that hunts at the water-air interface. The mouth is distinctly upturned (superior), well suited for snatching insects from the surface film.
The most diagnostic external feature is the extension of the ventral (pelvic) fins beyond the norm for the genus, a trait captured directly in the species name. Colouration is not extensively documented in accessible sources, but members of this group typically display iridescent scales on the flanks, subtle banding or spotting, and males develop more vivid colouration and longer fin filaments than females — a pattern consistent with other West African Epiplatys.
Habitat
The species occupies swamps and the swampy margins of small streams in savanna, a habitat description consistent across both FishBase and the CLOFFA records. It is restricted to the eastern side of the lower Niger River system and the northern Niger Delta in Nigeria, with the IUCN and AKA records also noting occurrence in Benin. Known collection localities include Awka, Ogun, the Ologbo River, the Orashi River, and Ughelli, as compiled in the AKA reference library.
The water at the type locality — swamps between Agwarba and Awka, southern Nigeria — falls within the savanna zone of southeastern Nigeria, where small streams and swamps are seasonal in character but retain permanent water bodies. FishBase records a pH of approximately 7 and a temperature of around 72 °F for this habitat. Because the species is a non-annual plant spawner, it is associated with permanent or near-permanent water that retains aquatic vegetation year-round, in contrast to truly seasonal pools exploited by annual killifishes of the same region.
Feeding
The CLOFFA faunal reference records the wild diet of Epiplatys longiventralis as ants and other insects, consistent with the surface-feeding, superior-mouthed morphology of Epiplatys generally. The upturned mouth and near-surface station allow the fish to take insects from the water surface film, and the proximity of savanna vegetation to swamp margins would make terrestrial insects a reliable food source.
In the aquarium the species will accept a range of live and frozen invertebrate foods — small chironomid (bloodworm) larvae, Daphnia, Artemia, and small fruit flies are all appropriate. Surface-delivered live food is especially effective. Prepared foods may be accepted once the fish is settled, but live or frozen foods should form the dietary core to maintain condition and encourage spawning.
Mating
Epiplatys longiventralis is a non-annual killifish, meaning it does not bury eggs in substrate peat or rely on diapause for development. Instead, pairs spawn near the water surface, depositing adhesive eggs on fine-leaved aquatic plants or onto floating spawning mops — a strategy that closely parallels the spawning behaviour described for the group in the AKA reference library. The courtship involves male display and pursuit of the female toward plant cover or a mop anchor point, where eggs are released and fertilised individually rather than in mass spawnings.
Males in breeding condition likely develop intensified colouration and extended fin filaments compared to females, as is typical of the genus. Sexual maturity in the aquarium is reached at approximately seven months of age, per the AKA source, which is consistent with the longer lifespan of non-annual species compared to the short-lived annual killifishes of the same biogeographic region.
Breeding
Spawning takes place near the water surface in plants or floating mops, with eggs deposited over an extended period of days or weeks rather than in a single batch. The AKA reference library records egg incubation in water at 12–14 days, with no diapausing phase — eggs complete development submerged and hatch into relatively large fry that are immediately capable of taking newly hatched brine shrimp (Artemia nauplii) as a first food, a characteristic of Epiplatys that simplifies early fry rearing.
The eggs are reported to measure approximately 0.5 in in diameter (CLOFFA reference), which is a meaningful size for a killifish egg, contributing to the large, well-developed fry at hatch. The species is noted in the AKA literature as difficult to breed successfully relative to more commonly kept Epiplatys — attention to water quality, provision of adequate surface vegetation or mops, and separation of eggs from the adults are important in captive breeding. Soft, slightly acidic water consistent with the species' native habitat is likely to give better results than neutral or alkaline conditions.
In the aquarium
Epiplatys longiventralis is a specialist species, best suited to killifish enthusiasts with experience in maintaining West African panchax. A small, species-only or panchax-only aquarium is appropriate — a tank of 15–20 US gal, well planted with fine-leaved surface vegetation and floating cover, provides the near-surface biotope the fish prefers. A tight-fitting lid is essential; like all small killifishes, it is an able jumper.
Water conditions should reflect the savanna swamp habitat: temperature around 72–75 °F, pH close to neutral (the FishBase record for the type locality is pH 7), and moderately soft water. Filtration should produce minimal surface turbulence, since the species feeds and spawns at the still water-air interface. Tankmates, if used at all, should be peaceful surface fish of similar size; in practice, most keepers maintain the species alone or in a small group to facilitate spawning observation and egg collection.
The species has a dedicated hobbyist following through the AKA and international killifish associations, and captive-bred stock occasionally circulates through society auctions and exchanges. Wild-caught material has been collected from multiple localities including the Ologbo and Orashi river systems, and locality data is recorded where known. The AKA rates the species as difficult, making it less suitable for beginners to the family.
Conservation
The IUCN Red List assessment, attributed to Olaosebikan (2020) with an assessment date of 2019, places Epiplatys longiventralis as Endangered — a status reflecting both its restricted geographic range within the Niger Delta and lower Niger basin and the ongoing loss and degradation of its savanna swamp habitat. The lower Niger and Niger Delta region of southeastern Nigeria is subject to intensive agricultural conversion, oil-field infrastructure, and associated water pollution that have reduced the extent and quality of small swamp systems that the species depends on.
Beyond habitat loss, the species faces the pressures common to West African swamp-associated killifishes: drainage for agriculture, sedimentation from land clearance, and the introduction of exotic species. Its known occurrence at a restricted number of localities — Awka, Ogun, Ologbo, Orashi, Ughelli, and adjacent areas — means that localised disturbance events can have disproportionate population-level effects. Captive populations maintained by killifish societies represent an important safeguard, and the AKA and affiliated organisations have a role in preserving genetic material from documented collection localities while wild habitat remains under pressure.