Taxonomy & naming
Fundulopanchax robertsoni was described by Austrian ichthyologist Arthur Radda together with Jorgen Scheel in 1974, with the original description published in Aquarium Journal 4(3):37–41. The species was originally placed in Aphyosemion — the catchall genus that dominated West African killifish taxonomy in the mid-twentieth century — as Aphyosemion robertsoni Radda & Scheel, 1974. Subsequent systematic revision transferred it to Fundulopanchax, a genus erected by Myers in 1924 to bridge the Atlantic divide between Fundulus and Panchax and now used for a cohesive assemblage of West and Central African non-annual killies. The FishBase synonyms list confirms Fundulopanchax robertsoni (Radda & Scheel, 1974) as the accepted name, with Aphyosemion robertsoni as the junior synonym.
Within Fundulopanchax, the species is assigned to the subgenus Paludopanchax — a grouping that unites the more swamp-associated, semi-annual species whose eggs evolved tolerance for seasonal drying but not the full diapause obligate in annual genera. Catalog of Fishes (Eschmeyer, CAS) is the governing authority for the valid combination. The authority appears in parentheses because the binomial was coined under a different genus than the one it now occupies.
Morphology
A small killifish, F. robertsoni reaches approximately 2 in in length, with FishBase recording a maximum of around 2.5 in SL/TL. The body plan is typical of the non-annual Fundulopanchax: moderately elongate, laterally compressed, and with the posteriorly placed dorsal fin that characterises the family. Fin formula from the WAK reference library gives D=16–18, A=18 — a relatively high fin-ray count for the subgenus.
As with most members of the genus, males are the more ornate sex, displaying the iridescent patterning and extended fin rays that hobbyists prize. Females are plainly coloured, shorter-finned, and rounder-bodied when carrying eggs. Eggs are described as small (approximately 0.5 in diameter), amber, and non-adhesive — a detail consistent with bottom deposition on fine substrate rather than adhesion to plant fibres.
Habitat
The type locality is a swampy area without surface outlet situated in a volcanic depression on the CDC rubber plantation approximately 1 mi north of Bolifamba, western Cameroon, at an elevation of around 984 ft. The pools are characterised by a surface covering of water lilies, shallow depth (2–6 in), and the capacity to dry out completely during drought. This combination — volcanic basin, impeded drainage, drying cycle — creates the conditions that shaped the species' semi-annual reproductive biology.
Water chemistry data from FishBase records pH 6, temperature 70 °F, and hardness around 50 ppm — soft, mildly acid, cool water consistent with highland forest seepage. The closed-basin nature of the site means there is no fish-community interchange with surrounding drainages; the pools exist as an ecological island, which explains both the species' morphological distinctiveness and the extreme narrowness of its range. A second known location, Yoke, is referenced in killifish hobby records under the collection code Yoke 89/14, suggesting a hobbyist collection made in 1989.
Feeding
In the wild, F. robertsoni almost certainly feeds as a micropredator on the invertebrates, small crustaceans, and insect larvae that colonise the shallow, vegetated pools of its type locality. No detailed wild diet study exists in the available literature, and the FishBase entry records diet category as 'commercial' — reflecting the lack of field data rather than any peculiarity in feeding habits.
In the aquarium, the species responds well to live and frozen small invertebrates: newly hatched brine shrimp, Daphnia, Moina, micro-worms, and small chironomid (bloodworm) larvae. Dry food can be accepted in time, but condition and colour are generally best maintained on live or frozen prey. Fry are reported as relatively large at hatching and able to take newly hatched brine shrimp nauplii from their first days of free-swimming life.
Mating
Fundulopanchax robertsoni belongs to the subgenus Paludopanchax, whose semi-annual reproductive strategy reflects the unpredictability of its seasonal swamp habitat. Unlike strictly annual killies such as Nothobranchius, which programme their eggs for obligate diapause, Paludopanchax species produce eggs capable of developing through in water as well as surviving extended damp or dry incubation — an adaptation to pools that may or may not desiccate in a given year.
Male F. robertsoni courts females with the lateral display typical of non-annual Fundulopanchax: spread fins, colour intensification, and positioning alongside the female near the substrate. Spawning occurs at or near the bottom, consistent with the species' classification as a bottom spawner. Eggs are deposited singly or in small numbers into fine substrate or accumulated organic material — peat, leaf litter, or fine sand — rather than on plant fibres or spawning mops, though mop spawning is sometimes reported in captivity.
Breeding
F. robertsoni has a reputation in the killifish hobby as a difficult species, and breeding accounts from BKA (British Killifish Association) newsletters reflect variable hobbyist success. The most consistent approach treats the species as a bottom/peat spawner with an extended but not obligate dry incubation.
Hobbyist protocol from the WAK reference library: eggs collected from peat or fine substrate are incubated dry (or barely damp) at 70 °F for 8–12 weeks before wetting. Wetting water should be cooler than the incubation temperature — around 61–64 °F — apparently mimicking the arrival of cool highland rains. Eggs measure approximately 0.5 in, are amber-coloured, and non-adhesive. Fry are described as large relative to egg size and accept newly hatched brine shrimp nauplii immediately. Sexual maturity is reached in approximately two months. An incubation period of 3–6 months is cited in some references, indicating that eggs are tolerant of extended storage; the optimal window of 8–12 weeks of dry incubation represents a practical middle ground supported by hobbyist experience.
In the aquarium
F. robertsoni is firmly a specialist fish — not because it is fragile, but because its requirements are narrow and its tolerance for inattention lower than common non-annual killies. Water conditions should mirror its highland volcanic-swamp origin: soft (targeting around 50 ppm or less), mildly acid (pH 6.0–6.5), and cool by tropical standards (68–72 °F). The WAK notes and BKA accounts agree that temperature management matters; overheating shortens the adult lifespan and degrades egg quality.
Because the species is known from only two locations and has not been exported in large numbers, captive stock should be managed carefully. Maintain pedigree strains separately, label stock by collection code, and avoid mixing Bolifamba and Yoke 89/14 populations unless doing so intentionally. A heavily planted or peat-filtered tank with subdued lighting suits the fish's biology and shows off the male's colouration. Housing a pair or trio in a dedicated 10–15 US gal species tank with a fine peat or sand base is the standard approach. Provide a lid: like all killifish, F. robertsoni is an accomplished jumper.
Conservation
The IUCN Red List assessed Fundulopanchax robertsoni as Data Deficient (DD) in 2009, with the assessment authored by T. Moelants. Data Deficient in this case does not reflect abundant populations that are simply understudied — it reflects genuine uncertainty about the persistence of a fish whose entire known natural range may amount to a single volcanic basin on a working rubber plantation in western Cameroon.
The type locality pools are seasonally desiccating and have no outlet; they are therefore inherently vulnerable to any change in the local hydrology or land use. The rubber plantation setting means the site is subject to ongoing agricultural management. Threats include drainage of swampy ground, alteration of shade canopy, introduction of non-native species, and simple accidental destruction of the pools during plantation operations. The species has been in hobby culture since the 1970s, and captive stocks held by killifish societies represent a genuine insurance population — an unusual situation where the hobby may be the primary safeguard for a species' genetic continuity. Specialist killifish organisations in Europe and North America should be the first port of call for anyone seeking stock.