Taxonomy & naming
Microctenopoma lineatum was first described by the American ichthyologist John Treadwell Nichols in 1923, originally placed in the genus Anabas as Anabas lineatus. Matthes (1964) subsequently noted that the holotype Nichols examined was likely a juvenile specimen, which had complicated early interpretations of the species. The current valid combination, Microctenopoma lineatum (Nichols, 1923), is confirmed in Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & van der Laan), which treats Anabas lineatus Nichols, 1923 as a synonym resolved under the genus Microctenopoma.
Microctenopoma is one of two African labyrinth fish genera within the family Anabantidae (the climbing gouramies), distinguished from the larger-bodied Ctenopoma by smaller adult size and details of ctenoid scalation and fin spine counts. The genus contains a cluster of small, forest-stream and swamp-dwelling species distributed across the Congo basin and neighbouring drainages. Within the genus, M. lineatum is diagnosed by its combination of 8–9 anal fin spines with 7–10 soft rays, and particularly by the two longitudinal dark stripes along the flanks.
Morphology
Microctenopoma lineatum is a small, elongate anabantid. FishBase records a maximum standard length of 2 in for males and 1.5 in for females, making this one of the more slender members of the genus. The body profile is moderately compressed laterally, giving the fish a cigar-like silhouette consistent with its benthopelagic lifestyle among aquatic vegetation and debris.
The most distinctive feature is the flanks, which carry two parallel horizontal dark stripes extending from the rear edge of the operculum to the base of the caudal fin — the character encoded in the specific epithet lineatum (striped). Background coloration is pale to tan, with the stripes appearing dark brown to blackish depending on light and mood. Fin coloration is unremarkable; the dorsal and anal fins bear the ctenoid spine complement typical of the genus. Sexual dimorphism within the species has not been described in detail in the available literature, but congeners typically show subtle differences in finnage and intensity of patterning between the sexes.
Habitat
Microctenopoma lineatum is recorded from two distinct drainage systems: the Gribingui River in the Central African Republic, which drains into the Lake Chad basin; and the Ubangi and Itimbiri rivers of the Democratic Republic of the Congo, both tributaries of the middle Congo River. This distribution across a drainage divide is notable and suggests the species tolerates a range of lowland freshwater conditions.
Like other members of Microctenopoma, this species is a facultative air-breather, possessing the labyrinth organ that allows it to extract oxygen directly from atmospheric air. This adaptation is characteristic of the family Anabantidae and permits occupation of warm, slow-moving, or seasonally oxygen-poor waters — flooded forest margins, densely vegetated creeks, swampy backwaters, and marshes. Closely related congeners such as M. ansorgii inhabit warm blackwater habitats with soft, acidic conditions; the precise water chemistry preferences of M. lineatum in the wild have not been formally documented, but the general ecology of the genus points to still or sluggish, well-vegetated freshwater environments.
Feeding
No specific diet study has been published for Microctenopoma lineatum. Based on the foraging ecology of other Microctenopoma species and small anabantids generally, the species is presumed to be an opportunistic predator of small invertebrates: aquatic insect larvae, small crustaceans, worms, and similar soft-bodied prey encountered in and around bottom vegetation.
In an aquarium setting, congeners accept a variety of small live and frozen foods — bloodworm, Daphnia, Artemia nauplii — and may eventually take high-quality small pellets once settled. Given the small maximum size (males to 2 in SL), prey items and pellet sizes should be scaled accordingly. Frequent small meals rather than occasional large ones suit the species' likely foraging style.
Mating
Microctenopoma lineatum has not been studied in detail in the wild, and direct reports of its mating behaviour in captivity are absent from the available literature. Based on the reproductive biology of closely related congeners — particularly M. ansorgii, which has been bred in aquaria — the species is expected to be a bubble-nester: the male constructs a floating raft of mucus-bound bubbles at the water surface, then courts the female and spawns with her beneath the nest.
In M. ansorgii and similar Microctenopoma, males can be territorial during the breeding period and may display aggressively toward one another or pursue females persistently. Optimal courtship conditions for the genus involve warm, slightly acidic water and dense vegetation that provides cover for the female and anchors or partially conceals the bubble nest. Temperatures around 79–81 °F and a pH near 6 have been reported to bring congeners into breeding condition.
Breeding
No published captive breeding account for Microctenopoma lineatum is known. Inference from the congener M. ansorgii — a species of similar size and ecology — suggests that the male builds and guards a floating bubble nest, and that the pair embrace beneath it during egg release in the manner typical of anabantid labyrinth fishes. Eggs are buoyant or float up into the nest; the male collects any sinking eggs and returns them. The female should be removed after spawning to prevent male aggression.
For congeners, incubation under the nest lasts a day or two at warm temperatures, and the male continues to guard the nest and young through the early free-swimming stage. The fry are very small at hatching and require infusoria or rotifers as first foods before graduating to newly hatched brine shrimp nauplii. Water quality in the rearing vessel is critical; gentle aeration only, as the fry need access to the surface film to gulp air and develop the labyrinth organ. Keeping the air above the water surface warm helps prevent chilling of the organ in newly emerged fry.
In the aquarium
Microctenopoma lineatum is rarely encountered in the aquarium hobby; its small size and retiring nature make it a niche fish suited to experienced keepers interested in the genus. A small, well-planted species tank — even 10–15 US gal — can house a pair or small group comfortably. Dense vegetation, floating plants to reduce surface light and anchor bubble nests, and dim overall lighting replicate conditions that allow the fish to display natural behaviour and reduce stress.
Water conditions should be warm (roughly 75–82 °F) and soft to moderately hard, slightly acidic to neutral — broadly consistent with the husbandry guidelines for M. ansorgii and other Congo-basin congeners. Filtration should be gentle; as a labyrinth fish, the species needs unobstructed access to the water surface to breathe atmospheric air, and a cover should be kept on the aquarium to maintain humid, warm air above. Tankmates, if any, should be small, peaceful, and slow-moving to avoid out-competing this shy species at feeding time. Given how infrequently it appears in trade, any captive individuals are likely wild-caught, making careful acclimatisation and quarantine especially important.
Conservation
Microctenopoma lineatum is assessed as Data Deficient (DD) on the IUCN Red List, with the assessment dated 6 May 2019. The Data Deficient designation reflects the absence of adequate population, distribution, and trend data to make a formal threat categorisation — not an inference that the species is secure. FishBase assigns the species a high resilience rating (population doubling time under 15 months), which is typical for small, short-lived fishes, but this refers to intrinsic demographic capacity rather than observed population status.
The two drainage systems from which the species is recorded — the Gribingui in the Central African Republic and the Ubangi–Itimbiri system in the DRC — span a region subject to ongoing habitat pressure from agricultural expansion, artisanal fishing, and forest loss. Until targeted surveys document population size and habitat condition across the range, the true conservation status of M. lineatum will remain unknown. The priority need is basic field inventory.