Taxonomy & naming
Mastacembelus praensis was described by Travers in 1992, with the type locality in the Pra River drainage of Ghana and Nigeria. The species epithet praensis is a Latinised adjective meaning 'of the Pra', referring directly to the river from which the type series was collected — a straightforward toponym in the tradition of descriptive ichthyology.
The Catalog of Fishes (Eschmeyer, the authoritative register for valid names) places it in the genus Mastacembelus, the type genus of the family Mastacembelidae, within the order Synbranchiformes. This order also contains the swamp eels (family Synbranchidae), and the two families are far closer to one another than either is to the true eels of the order Anguilliformes. The spiny-eel body form is therefore convergent with that of the marine Anguilla and its relatives, not homologous. African Mastacembelus were historically partitioned among several genera — Aethiomastacembelus, Caecomastacembelus, and Afromastacembelus — before being consolidated back into Mastacembelus. M. praensis has always sat within this African clade and is not affected by the Asian Macrognathus or Sinobdella splinter groups.
Morphology
Like all Mastacembelidae, M. praensis has a markedly elongate, laterally compressed body that tapers evenly to a pointed tail. The dorsal surface carries a row of short, isolated spines — the defining character of the family — running ahead of the soft dorsal fin, which sweeps continuously around the tail and into the anal fin. The snout is drawn out into a fleshy, trunk-like rostral appendage tipped with tubular nostrils, an organ of chemosensory probing well-suited to foraging in soft substrate and among leaf litter.
FishBase records a maximum standard length of 14 in for the species. The body is visually scaleless — tiny embedded scales lie beneath a heavy mucus coat — and the skin is correspondingly sensitive. Published meristic and colouration detail for this species is sparse in the wider literature, as formal morphological description comes primarily from the original 1992 account; no vivid colour pattern is on record for M. praensis comparable to the better-studied fire eel or tire-track eel of the Asian Mastacembelus.
Habitat
Mastacembelus praensis is a freshwater fish native to the Pra River basin and associated drainages of the West African coastal belt, within the countries of Ghana and Nigeria. The Pra is a lowland river system draining the Ashanti uplands to the Gulf of Guinea, characterised by warm, modestly turbid waters with soft to lightly mineralised chemistry typical of West African coastal rivers — broadly near-neutral pH and temperatures in the mid-to-upper twenties Celsius.
Like the other West and Central African Mastacembelus, it is most likely a fish of flowing and seasonally flooded riverine environments — riffle edges, forested stream margins, and floodplain pools — where it can burrow into sandy or muddy substrate by day and emerge after dark to forage. Seasonal flooding and rain-driven water level fluctuations probably trigger its reproductive cycle, as they do for other spiny eels in the region. Detailed habitat surveys for this species are absent from the accessible literature.
Feeding
Mastacembelus praensis is almost certainly a nocturnal, benthic carnivore in the mould of all Mastacembelidae. The family as a whole forages by probing soft substrate and leaf litter with the rostral appendage, seeking out insect larvae, worms, small crustaceans, and similar benthic invertebrates; larger species also take small fish.
No specific dietary study of M. praensis is published in the accessible literature, but the body plan — elongate, flattened venter, sensitive probing snout, small underslung mouth — is diagnostic of a substrate-working invertebrate feeder. In any aquarium setting it should be offered meaty, sinking foods in the evening: bloodworm, earthworm, and other benthic invertebrate prey, delivered after the lights dim.
Mating
Mastacembelus praensis is a spiny eel and, as such, is an egg-scattering substrate spawner — not a catadromous migratory species like the true eels, and not a bubble-nest builder like the swamp eels of family Synbranchidae. It breeds in fresh water. In line with the breeding biology documented for related West and Central African Mastacembelus, spawning is almost certainly triggered by the seasonal rains and associated rise in water level and temperature, which prompt adults to move onto flooded margins and scatter adhesive eggs among aquatic vegetation, roots, or leaf litter.
No published courtship observation specific to M. praensis has been located. Extrapolating from close relatives, a courting pair is likely to circle and entwine before releasing eggs, with no nest construction and no continuing parental bond. The adults do not guard or tend the eggs after spawning.
Breeding
As with virtually all spiny eels found in West African rivers, M. praensis is not bred in the home aquarium in any documented sense — it is an obscure species rarely available to hobbyists, and no captive-breeding account has been published or widely circulated. The family-level expectation is that adhesive eggs are scattered freely among fine plants or root tangles and receive no parental care, hatching within a few days at tropical temperatures to produce small, demanding larvae.
Were a keeper to attempt breeding, the approach would follow that used for other mid-sized African Mastacembelus: a large, well-matured aquarium with a sand substrate and dense plant cover, a conditioned pair identified by the female's greater girth when gravid, and a simulated dry-to-wet-season transition via gradual cooling followed by large changes with slightly softer, warmer water. Success at this scale remains in the realm of the specialist rather than the general hobbyist.
In the aquarium
Mastacembelus praensis is a very rarely traded species and is almost never available through normal aquarium supply chains. For a keeper fortunate enough to obtain one, the care requirements are broadly those of the African spiny eel group: a well-covered aquarium (spiny eels are notorious escape artists that will exploit any gap, slip from the water, and perish on the floor — a tight, sealed lid is non-negotiable), a deep bed of soft sand for burrowing, and caves or pipe sections for daytime retreats.
At up to 14 in, it is a manageable but not tiny fish and should be housed with robust tankmates too large to be swallowed. Like all Mastacembelidae it is scaleless and acutely sensitive to copper-based medications and to the osmotic stress of poor water quality; a mature, stable filter and careful medication choices are essential. Meaty foods offered in the evening — bloodworm, earthworm, chopped seafood — suit its nocturnal foraging habit. It should not be expected to compete openly with faster, more active fishes at feeding time.
Conservation
Mastacembelus praensis has not been evaluated by the IUCN Red List and carries a status of Not Evaluated (NE). The species is known from a geographically restricted range centred on the Pra River drainage of Ghana and, at least historically, from Nigeria, giving it a naturally limited distribution by comparison with the widespread pan-African Mastacembelus species.
The West African coastal river zone faces ongoing pressures from agricultural runoff, small-scale gold mining (notably in Ghana's river systems), deforestation of riparian zones, and water abstraction — all of which degrade the clear, well-oxygenated flowing-water habitat that spiny eels require. For a narrow-range, data-sparse species with no IUCN assessment, the precautionary reading is that localised threats could be significant even without a formal determination of status. Formal survey of its current range extent and population health would be a worthwhile step toward understanding whether a Red List category is warranted.