Taxonomy & naming
Plataplochilus loemensis was described by Jacques Pellegrin in 1924, with a type locality in the Lombo River — now known as the Koulombo — a tributary of the Loémé River in southwestern Gabon. The specific epithet loemensis is a Latinised toponym referring to the Loémé River system, the drainage from which the type material was collected. The species was originally placed in the genus Haplochilus, a broad historical repository for many small African egg-laying killifish; subsequent revision placed it in Plataplochilus, a genus now containing nine accepted species distributed across the rainforest streams of West and Central Africa.
Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) recognises the current valid combination as Plataplochilus loemensis (Pellegrin, 1924). The parenthetical authority reflects the generic transfer from the original Haplochilus placement. The genus Plataplochilus belongs to the family Procatopodidae (the African lampeyes), a group of small, schooling, non-annual killifish characterised by the iridescent supraorbital light organ. Lambert (1967) and Wildekamp (2004) provide key treatments of the West and Central African procatopodid fauna and are standard references for the genus.
A 2022 paper describing the related species Plataplochilus eliasi provided updated morphometric comparisons for the genus and includes data on P. loemensis body proportions — body depth at 30.7–33% of standard length — placing it among the deeper-bodied members of the genus.
Morphology
Plataplochilus loemensis is a small, slender to moderately deep-bodied killifish reaching approximately 2.5 in total length (FishBase). The body is laterally compressed and the profile is typical of schooling lampeyes: a rounded snout, a terminal to slightly upturned mouth suited for surface and mid-water feeding, and a relatively large eye dominated by the iridescent blue-green patch of the supraorbital light organ that gives the lampeyes their common name and their group identity in the hobby.
Colouration in life is characteristic of the procatopodid lampeyes: males are more vividly marked than females, typically showing iridescent blue-green or turquoise tones on the flanks and an accentuated light-organ patch, while females are plainer and more uniformly coloured. The fins are relatively clear to lightly pigmented. Sexual dimorphism is mild beyond the colouration difference; females are noticeably fuller-bodied when gravid.
Habitat
The Loeme lampeye is native to the coastal rainforest drainage systems of a compact zone along the Atlantic seaboard of western Central Africa. Confirmed distribution records span the Lombo (Koulombo), Loémé, Kouilou, and Chiloango rivers as well as minor lower-Congo tributaries, encompassing parts of southwestern Gabon, the Republic of Congo, Cabinda (the Angolan exclave), and the far western Democratic Republic of Congo. FishBase records the species from this suite of rivers within the coastal rainforest belt.
Within these systems, P. loemensis inhabits small rivers, brooks, and swamp margins — the permanently watered, shaded environments typical of lowland Atlantic rainforest streams in the region. Water chemistry recorded for the species is near-neutral to mildly acidic: pH 6.5–7.2, temperature 72–77 °F. The water is freshwater throughout the species' range; the coastal forest streams are generally clear and well-oxygenated where they flow, with shaded, root-lined margins providing shelter and spawning habitat. The species is benthopelagic and non-migratory, remaining associated with its home drainage rather than undertaking seasonal movements.
Feeding
Like other procatopodid lampeyes, Plataplochilus loemensis is a micro-predator and opportunistic feeder adapted to catching small invertebrates — zooplankton, aquatic insect larvae, small crustaceans, and surface-fallen terrestrial insects — in the mid-water and near-surface zones of its forest stream habitat. The upturned mouth position facilitates surface feeding, a common adaptation in lampeyes that regularly exploit the film of small invertebrates and emerging insects at the water surface.
In the aquarium the species accepts live and frozen small invertebrates (Daphnia, Artemia nauplii, micro-worms, blackworm) without difficulty. Varied live and frozen foods are preferable to dry diets alone; the species does best when offered a diet that mimics the diversity of small invertebrate prey available in its native forest streams.
Mating
Plataplochilus loemensis is a non-annual killifish with a continuous, prolonged spawning strategy. This reproductive mode contrasts sharply with the annual killifish — which produce drought-resistant diapausing eggs buried in dried pond substrate — and reflects the species' adaptation to permanent-water environments where no dry season eliminates the water body and enforces dormancy. As a procatopodid lampeye, P. loemensis spawns repeatedly over an extended period rather than in a single mass event.
The species is a crevice spawner or plant-root spawner depending on the substrate available — the German specialist literature (killifische.info) classifies it as a Leuchtaugen-Spaltenlaicher, literally a 'lampeye crevice-spawner'. In nature, pairs or small groups deposit a small number of adhesive eggs at a time among fine roots, leaf litter, aquatic vegetation, or in rocky or woody crevices along the stream margin. Males display to females using the iridescent supraorbital light organ and body colouration; the spawning act involves lateral close-contact positioning and simultaneous release of eggs and milt onto the attachment substrate.
Breeding
Because P. loemensis is a continuous spawner rather than an annual, eggs are produced in small batches over weeks and months rather than in a single synchronised clutch. The adhesive eggs are attached individually or in small clusters to fine-leaved plants, roots, or crevice surfaces. Incubation period at the species' preferred temperature range of 72–77 °F is consistent with other small non-annual procatopodids — typically one to several weeks depending on temperature — and the eggs do not require any drying or dormancy period. Fry hatch as miniature versions of the adults and are sufficiently large to take Artemia nauplii as first food.
In the aquarium, dedicated breeding set-ups use dense clumps of fine-leaved vegetation (Java moss, hornwort) or spawning mops to collect eggs. Adults should be conditioned on live and frozen invertebrates. Because continuous spawning means eggs and fry may be present at various stages simultaneously, a separate rearing tank for collected eggs or fry is advisable. The species is reported to be difficult to maintain in aquaria (FishBase), likely reflecting sensitivity to water quality and the need for stable, clean water within its preferred chemical range.
In the aquarium
The Loeme lampeye is an uncommon species in the wider hobby but is regularly kept by members of specialist killifish societies; the American Killifish Association database records ten Journal of the American Killifish Association articles referencing the species across the period 1983–2013, indicating sustained hobbyist interest. The AKA classifies it in the broad grouping of 'all other Old World' killifish, reflecting the still-developing understanding of West-Central African lampeye husbandry compared with the more widely kept annual species.
FishBase characterises the species as difficult to maintain in aquaria. In practice, a well-set-up tank replicating its native forest-stream conditions — soft to neutral, well-filtered water at 72–77 °F, dim lighting, dense planting or root tangles, and co-inhabitants small enough not to compete or predate — gives the best results. A slightly acidic to neutral pH (6.5–7.2) and temperatures at the lower end of the tropical range suit the species. Because it is a schooling fish in nature, it is best kept in groups; solitary individuals or pairs without conspecific social structure tend to fare poorly. The species should not be combined with significantly larger or aggressive fish. It is suited to specialist collections focused on African lampeyes or West-Central African stream biotopes.
Conservation
The Loeme lampeye is assessed by the IUCN Red List as Least Concern (LC), the assessment having been published in 2009. The relatively broad distribution across several river systems — spanning the Loémé, Kouilou, Chiloango, and lower-Congo minor tributaries in parts of Gabon, the Republic of Congo, Cabinda, and the DRC — underpins this status, since the species is not restricted to a single drainage or spring system vulnerable to a single discrete threat.
Nonetheless, the coastal Atlantic rainforest belt of western Central Africa is under significant and ongoing pressure from logging, agricultural conversion, and infrastructure development, all of which degrade the shaded, clear-water stream habitats on which this species depends. Increased sedimentation from deforestation reduces water clarity and smothers spawning substrates; altered hydrology from land clearance can shift the temperature and flow regime of small forest streams beyond the species' tolerance. The AKA database records Gabon as a high-confidence occurrence and the Republic of Congo as low-confidence, suggesting that the western portion of the range — in better-preserved Gabonese rainforest — may be the most ecologically secure population. Ongoing monitoring of forest-stream killifish in this region, linked to broader Atlantic rainforest conservation, is the principal safeguard for the species.