Taxonomy & naming
Aphyosemion lividum was described by Legros and Zentz in 2007 in the killifish journal Killi-Contact (volume 35, number 6, pages 1–34). The holotype is a male measuring 1.5 in standard length (2 in total length), collected at Ntoumba, Cameroon, on 24 February 2005. The species is placed in the subgenus Mesoaphyosemion (sometimes written Mesaphyosemion), within the calliurum species group — a cluster of closely related West and Central African killifish united by shared morphological and colour characters. The American Killifish Association classifies this group as Class 9 (Mesaphyosemion / Calliurium types).
The specific epithet lividum is Latin for 'bluish' or 'livid', referring to the prominent blue colouration of the body and fins in males. The genus name Aphyosemion is a compound of the Greek aphyo (small fish) and semeion (mark or flag), an allusion to the flaglike, often elaborate finnage of the males. Eschmeyer's Catalog of Fishes records the valid combination as Aphyosemion lividum Legros & Zentz, 2007. Some references list it under the subgenus name Scheelsemion, which reflects an alternative subgeneric arrangement sometimes applied to calliurum-group members.
The species is diagnosed from its congener Aphyosemion ahli principally by the blue-rose colouration of the flanks and by the absence of vertical red striations on the caudal peduncle — a character combination that holds across all known collection sites. Meristic counts are D = 11–12, A = 13–15, with the dorsal fin origin approximately six to eight scale rows anterior to the anal fin origin (D/A offset = +6–8), and approximately 29 + 3 lateral scales.
Morphology
Aphyosemion lividum is a slender, laterally compressed killifish reaching a maximum recorded standard length of 1.5 in in males (FishBase). The body form is typical of the calliurum group: an elongate trunk, a rounded caudal fin, and moderately developed dorsal and anal fins that are positioned well back on the body, a hallmark of the Aphyosemion bauplan. The holotype male measured 1.5 in SL.
Males are the ornamental sex, displaying a ground colour described as blue-rose on the flanks — a warm interaction of blue iridescence and pinkish-red pigment that gives the species its name. The caudal peduncle and caudal fin carry colour markings consistent with calliurum-group patterning, but crucially lack the vertical red striations on the caudal peduncle that characterise Aphyosemion ahli, making this the primary field-identification character separating the two species. The WAK reference library notes that colour variability across the known collection sites is low, suggesting a stable phenotype across the species' restricted range.
Females are cryptically coloured in the subdued brownish tones typical of Aphyosemion females, lacking the iridescent flank markings of males and with less developed finnage — the standard pattern of sexual dichromatism within the genus.
Habitat
Aphyosemion lividum is known from two areas east and south of Edéa in the coastal lowlands of Cameroon — a region drained by the Sanaga River and the Nyong River systems (FishBase). Collection localities on record include Ntoumba (the type locality, collected February 2005 under code BLLMC 05/34), and a second site coded ABC 06/94, along with the locality Apouh. All are in the humid equatorial lowlands of south-central Cameroon, a landscape dominated by dense secondary and gallery forest over lateritic soils.
The WAK (Killifish of West Africa) database describes the habitat at type-locality as deep-brown water with high tannin content and a thick base of terrestrial leaf litter on the stream or pool floor. This is the classic West African forest-killi microhabitat: shallow, slow or stagnant water, heavily shaded by closed canopy, stained dark by humic acids, with pH values likely in the mildly to strongly acidic range and very low mineral content. The AKA notes that more demanding Aphyosemion species — a category into which calliurum-group members frequently fall — benefit from softer, more acidic water particularly for breeding, consistent with the conditions documented at the type locality.
As a non-annual killifish, Aphyosemion lividum inhabits water bodies that persist year-round or remain wet through the dry season, in contrast to the temporary savanna pools occupied by annual species. The species' use of a deep leaf-litter substrate as both refuge and spawning microhabitat is characteristic of the group.
Feeding
Like all members of the genus, Aphyosemion lividum is a carnivore that feeds on small invertebrates in the wild. In the leaf-litter and tannin-water microhabitat it occupies, the diet would consist primarily of small aquatic insects and their larvae, microcrustaceans, worms, and other zooplankton-scale prey drawn from the rich invertebrate community associated with decomposing leaf litter on forest stream floors.
In captivity, Aphyosemion killies of this size and group are straightforward to feed: they accept live and frozen foods readily — Daphnia, mosquito larvae (black and white), Artemia nauplii, micro-worms, and Grindal worms are all standard fare. Many individuals will also take high-quality dried foods of appropriate size, though a diet with a substantial live or frozen component keeps fish in better colour and reproductive condition. Because they are small fish (under 1.5 in), food items must be correspondingly fine.
Mating
Aphyosemion lividum is a non-annual killifish and a plant and mop spawner — the reproductive mode that characterises the majority of Aphyosemion species from permanent or near-permanent water. Unlike annual killies that bury eggs in substrate for a drying-phase diapause, non-annual species like A. lividum spawn continually over an extended period, with pairs depositing individual adhesive eggs on fine-leaved plants, moss, or floating spawning mops near the surface or among the leaf litter of the substrate.
The mating act is a brief spawning embrace typical of the genus: the male courts the female with fin displays, drives alongside her, and the pair press together as a single egg is released and fertilised. This is repeated many times over days and weeks rather than in a single mass-spawning event. Males of the calliurum group are active courters and will pursue females persistently; in a confined aquarium it is advisable to keep more than one female per male or to provide visual refuges so females can escape male attention.
No specific mating observations are on record in the WAK database for this species, but behaviour consistent with the calliurum-group pattern — continuous low-level spawning among well-conditioned adults in a decorated tank — is the expected norm.
Breeding
Breeding Aphyosemion lividum follows the standard non-annual Aphyosemion protocol. Eggs are adhesive and are deposited individually on fine-leaved plants, Java moss, or synthetic spawning mops placed near the surface or resting on the bottom. The eggs are typically collected by hand or by removing and replacing the mops, and incubated separately in small containers of soft, slightly acidic water at a temperature consistent with the collection locality (low-to-mid 20s °C is usual for Cameroonian forest killies).
Incubation in water — not in moist peat — takes two to three weeks at typical room temperatures, after which the fry hatch directly as miniature adults capable of taking Artemia nauplii or micro-worms from the outset. There is no diapause requirement; the eggs develop continuously in water without any dry phase. Fry are sensitive to water quality and benefit from small, frequent water changes with well-matched, soft, slightly acidic water. Growth is moderate and fish reach sexual maturity within several months.
Longevity is typically two to three years in well-maintained aquaria, consistent with other non-annual West African Aphyosemion. The WAK reference notes no published breeding data specific to A. lividum, but breeders working within the AKA classification system will find it tractable under the standard calliurum-group protocols.
In the aquarium
Aphyosemion lividum is a specialist fish suited to the dedicated killifish keeper rather than the general community aquarist. At under 1.5 in, it requires a small, calm, well-planted tank — a species aquarium of 5.5–10 US gal is entirely adequate for a pair or trio. The tank should be tightly covered, as all Aphyosemion are capable jumpers. Gentle, low-flow filtration preserving the still, leaf-litter microhabitat is preferable; a simple sponge filter is ideal.
Water chemistry should target the soft, acidic conditions of the type locality: temperature in the low-to-mid 20s °C (approximately 72–77 °F), pH in the 5.5–6.8 range, and minimal hardness. Tannin-stained water achieved through dried oak or Indian almond leaves on the substrate both matches the natural habitat and reduces pathogen pressure. The species has not been assigned a formal water parameter range in the available references, and the above figures extrapolate from habitat description and genus-level guidance rather than direct measurement — they should be treated as a working starting point.
Aphyosemion lividum appears in the AKA's WAK database and is kept by killifish specialists in Germany and North America. Its low colour variability across collection sites and the limited number of known collection localities mean it is less commonly encountered than more variable calliurum-group members. Hobbyists maintaining it should prioritise accurate locality data — labelling fish and spawn with the collection code (BLLMC 05/34, ABC 06/94, or Apouh) is standard practice in the killifish community to preserve strain integrity.
Conservation
Aphyosemion lividum has not been assessed by the IUCN Red List and carries a status of Not Evaluated (NE). Its known distribution is confined to two areas east and south of Edéa in the Sanaga and Nyong lowlands of Cameroon — a restricted footprint that, combined with its association with intact lowland forest microhabitats, places it in a category of potential vulnerability.
The coastal lowlands of Cameroon where A. lividum occurs are among the more heavily deforested regions of West-Central Africa. Expansion of oil palm plantations, logging, small-scale agriculture, and urban growth around Edéa and Douala have reduced and fragmented the gallery forest and seasonal streams that West African killifish depend on. Sedimentation and altered hydrology following canopy removal degrade the leaf-litter microhabitats these fish inhabit. Introduction of non-native species — Nile tilapia, mosquitofish, and other broadly tolerant fishes entering via aquaculture escapes or mosquito-control programmes — poses an additional risk in small, enclosed water bodies.
Within the killifish hobby, the species is maintained by specialist breeders affiliated with the AKA and European killifish clubs, and captive stocks may represent an important genetic archive for population localities that could be threatened in the wild. A formal field survey of the type locality at Ntoumba and the ABC 06/94 and Apouh collection sites, combined with an IUCN assessment, would give a clearer picture of the species' conservation status.