Taxonomy & naming
Callopanchax sidibei was described by Rainer Sonnenberg and Wolfgang Busch in a 2009 paper published in the Bonn Zoological Bulletin (57(1): 3–14), where it was placed in the genus Callopanchax within the family Nothobranchiidae, subfamily Epiplateinae. The authority is presented in parentheses because the name has been subject to subsequent revision; earlier literature may refer to the species as Callopanchax sidibeorum (an orthographic variant used on FishBase and some older sources), but the Catalog of Fishes (Eschmeyer, CAS) is the governing authority for the valid binomial. The genus Callopanchax currently contains a small number of West African annual killifish species sharing a coastal forest and savanna distribution from Sierra Leone to Nigeria.
The specific epithet sidibei honours an individual associated with the collection or fieldwork in Guinea; the original description provides the full etymology. The type locality is recorded as Bombokoré, with collection code GM 97/2, in the Kindia region of Guinea at approximately 9°32.71'N, 13°14.51'W — a site characterised by shallow, shaded water bodies adjacent to secondary forest.
Morphology
Callopanchax sidibei is a small killifish: FishBase records a maximum standard length of 2.5 in for males and 2.5 in for females, making the sexes essentially the same size. As in other members of the genus, males are considerably more vividly coloured than females, displaying the rich iridescent patterning typical of West African forest annuals — bright flanks contrasting with red, blue, or yellow fin markings that function in courtship and male–male signalling. Females are cryptically brown, providing camouflage in the leaf-litter substrates where the species spawns.
The body form is typical of Callopanchax and the broader epiplatin radiation: moderately robust, slightly laterally compressed, with a blunt snout and a large upturned mouth suited to surface and mid-water feeding. Scales are moderately large and cycloid. The caudal fin is rounded to lanceolate in males. Like all annual killifish, the body is adapted for rapid growth and early sexual maturity — essential when the entire active life of the fish may span only four to six months between the rains' arrival and the next dry-season desiccation.
Habitat
In the wild, Callopanchax sidibei occupies a narrow ecological niche: shallow temporary water bodies in and around secondary forest in the Kindia region of southwestern Guinea. These include forest pools formed by rainwater accumulating in natural depressions, pools in rubber plantation clearings, slow-flowing ditches, and stream-margin stagnations. Field observations from the type locality record water depth of approximately 8 in over a sandy base covered in decaying leaves and submerged wood — classic tannin-stained, leaf-litter habitat. Water is clear at the type site despite the organic loading.
Water chemistry measured in the field indicates extremely soft, acidic conditions: pH 5.2 and hardness of 10 dGH (roughly 3–4 °dH general hardness equivalent), with a surface temperature of 81 °F recorded during collection. These figures reflect the soft, mineral-poor, rain-fed blackwater conditions typical of West African forest killifish habitat. The species prefers shaded positions and is associated with areas sheltered from direct sun by the surrounding forest canopy. Outside the rainy season, when surface pools dry completely, the species persists only as buried eggs in the substrate.
Feeding
Like other epiplatin killifish of comparable size, Callopanchax sidibei is a micropredator, feeding opportunistically on small invertebrates available at and below the water surface: aquatic insect larvae, microcrustaceans, small worms, and terrestrial invertebrates that fall onto the water. The upturned mouth is well suited to surface feeding, a common feeding station for killifish in still or slow-moving water where emergent insects are abundant.
In the aquarium, the species accepts live and frozen foods readily — artemia nauplii and adults, daphnia, chironomid larvae (bloodworm), and tubifex are all suitable staples. Dry foods are taken by some individuals but live and frozen items are preferable for conditioning breeding pairs. Because the fish are small and the mouth gape is moderate, food items should be sized appropriately; oversized prey is refused.
Mating
Callopanchax sidibei is a substrate-spawning annual killifish whose reproductive behaviour centres on the burial of eggs in soft sediment. Courtship is initiated by the male, who displays intensified colouration and pursues the female with lateral S-curve body postures — the typical killifish courtship display — spreading his fins to show their full chromatic extent. The male manoeuvres alongside or slightly below the female, and when she is receptive, the pair press together flank-to-flank or the male curves around her.
At the moment of spawning, the pair dive into the soft substrate — peat, mud, or accumulated leaf detritus — burying themselves briefly while eggs and sperm are released simultaneously. Each spawning dive deposits one or a small number of eggs, and the pair return to open water before repeating the sequence. Males in peak condition display vigorously and court repeatedly through the active season. The soft, dark substrate is an essential spawning trigger; pairs will not spawn productively over hard or barren substrates.
Breeding
The eggs of Callopanchax sidibei are adhesive and buried in soft sediment, where they undergo diapause — a state of arrested development that allows them to survive the complete desiccation of the pool during the dry season. Research on annual killifish embryology documents that eggs of species in this group can pause development at one or more of three distinct embryonic stages, and that the duration of the dry season determines how long the eggs remain dormant. In the wild, the incubation period spans approximately two to nine months — the full length of the dry season — before the return of rain and refilling of the pool triggers hatching.
In the aquarium, the standard technique is to maintain breeding pairs over a deep layer of soft peat or coconut coir into which they spawn freely. After several weeks of spawning activity, the medium is removed, squeezed gently to remove excess moisture, and stored in a sealed plastic bag at moderate temperature for an appropriate diapause period — typically three to six months for West African Callopanchax. Hatching is induced by re-wetting the peat with slightly aged, soft, acidic water. Fry are large relative to the egg size at hatching and can take artemia nauplii from the first feeding day. Growth is rapid; fish may reach sexual maturity in as little as two to three months under warm conditions, reflecting the urgency of the annual life cycle.
In the aquarium
Callopanchax sidibei is a species for the dedicated killifish specialist rather than the general community aquarist. A breeding pair or a small group (one male to two or three females) can be maintained in a modest aquarium of 10–15 US gal, heavily planted or decorated with dried Indian almond leaves, driftwood, and a soft substrate of peat or fine sand to replicate the leaf-litter forest floor. The low light, dark substrate, and tannin-staining of the water both suit the fish's wild habitat preference and bring males into peak colouration.
Water should be soft and acidic: pH 5.5–6.5 and very low hardness, matching the field values recorded at the type locality. Temperature of 72–79 °F is appropriate; the species does not require elevated temperatures and may be stressed above 82 °F in a closed aquarium. Efficient, gentle filtration is important — a sponge filter is ideal — but the flow must remain very low, as these are fish of still and barely moving water. Males can be aggressive toward each other; a single dominant male should be kept per tank unless the space is generous and sightlines are broken by vegetation or decor.
A deep layer of spawning medium (peat or coir, minimum 2 in) must be provided for breeding. Conditioning feeds of live and frozen invertebrates raise the pair into spawning condition within a few weeks. The species is not long-lived even under ideal conditions — one to two years is a realistic expectation — and maintaining a captive population requires a managed peat rotation to ensure a steady supply of developing eggs.
Conservation
Callopanchax sidibei has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated (NE). This absence of assessment does not reflect ecological security. The species is known from a restricted area of southwestern Guinea centred on the Kindia region, and its habitat — shallow seasonal pools and forest-edge ditches in secondary forest — is precisely the type of microhabitat most vulnerable to agricultural conversion, rubber and palm plantation expansion, road construction drainage, and the drying effects of deforestation on the local water cycle.
The annual killifish life history, while resilient to natural seasonal desiccation, offers little buffer against permanent habitat loss. When a pool is drained, bulldozed, or chemically contaminated, the eggs in the substrate are destroyed with it, and there is no dispersal pool of adults to recolonise. For single-locality or narrow-range endemics like this species, the loss of even a handful of breeding pools can eliminate a population entirely. The killifish community has expressed ongoing concern about the pressures on Guinea's coastal forest killifish fauna, and formal evaluation of the species' range extent and population trends would be a valuable first step toward any protective action.