Taxonomy & naming
Campellolebias dorsimaculatus was described by Wilson J. E. M. Costa and Roberto E. Lazara in 1994, based on material collected from the Ribeira de Iguape River basin in the state of São Paulo, Brazil. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) recognises the valid combination as Campellolebias dorsimaculatus Costa & Lazara, 1994.
The genus Campellolebias is a small South American annual killifish genus placed within the family Rivulidae (now frequently assigned to the order Cyprinodontiformes). The genus is closely allied to other southeastern Brazilian annual killifish genera. Campellolebias is restricted to coastal Atlantic Forest drainages of southern and southeastern Brazil, a region of extraordinarily high endemism among freshwater fishes.
The specific epithet dorsimaculatus is Latin, combining dorsi- (genitive of dorsum, back or dorsal surface) with maculatus (spotted), meaning 'spotted on the back' — a reference to the dorsal patterning that distinguishes this species from its congeners.
Morphology
Campellolebias dorsimaculatus is a small, laterally compressed killifish reaching a maximum recorded total length of approximately 1.5 in (FishBase), with males typically somewhat smaller or similar in size to females in this genus. The body form is typical of the rivulid annual killifishes: moderately deep, rounded in cross-section, with a slightly upturned mouth suited to surface and mid-water feeding.
Sexual dichromatism is pronounced, as in virtually all rivulid killifishes. Males display vivid body colouration with iridescent lateral flanks and the characteristic dorsal spotting or patterning implied by the species name. The dorsal and caudal fins of males are typically marked with colour, and breeding males intensify considerably. Females are cryptically coloured in brown and olive tones with subdued patterning, an adaptation to life in leaf-littered forest-floor pools where camouflage matters more than display.
The body proportions, fin placement, and scale pattern are consistent with other Campellolebias species; formal morphometric data distinguishing dorsimaculatus from its congeners are contained in the original description by Costa & Lazara (1994).
Habitat
In the wild, Campellolebias dorsimaculatus inhabits shallow, temporary pools and seasonal streams within primary Atlantic Forest in the Ribeira de Iguape River basin, São Paulo state, Brazil. These habitats are characterised by soft, acid blackwater — It Rains Fishes records a pH preference of 5.0–5.5 — with low hardness, dense leaf litter, and a substrate of peat, mud, and decomposing organic material. The pools typically occur on the forest floor in areas with dense canopy cover, which maintains humidity, shade, and acidic chemistry through tannin leaching from fallen leaves.
Water temperatures in these forest-floor microhabitats are moderated by canopy shade, ranging from approximately 64–79 °F (It Rains Fishes). FishBase documents a slightly broader captive-tolerant range of 72–82 °F at pH 6.5–7.2, though the species' preferred wild conditions are significantly more acidic. The defining characteristic of the habitat is seasonality: these pools fill during the Atlantic Forest wet season and dry out completely during the dry season, a cycle that drives the annual life history of the species.
The Ribeira de Iguape basin retains some of the largest remaining contiguous blocks of Atlantic Forest in Brazil, though forest cover has been dramatically reduced from its pre-colonial extent. The species is non-migratory, entirely dependent on the micro-habitat of these ephemeral forest pools.
Feeding
Campellolebias dorsimaculatus is a carnivore, feeding on small invertebrates, zooplankton, insect larvae, and other small aquatic prey available in its seasonal pool habitat. The annual killifish life cycle places a premium on rapid growth and early reproduction, so the diet must deliver sufficient protein and energy for fish to reach reproductive maturity within weeks of hatching.
In captivity, this species is reported to accept live foods readily — Artemia nauplii and small live prey — but reportedly refuses dried or frozen foods (It Rains Fishes). This strong preference for live prey is typical of many seasonal killifishes and reflects a hunting strategy calibrated to small, moving prey items in the forest pool environment. Successful long-term maintenance in aquaria therefore requires a reliable supply of live or at minimum frozen food items.
Mating
Campellolebias dorsimaculatus is a substrate-spawning annual killifish. Mating behaviour follows the classic rivulid pattern: a receptive pair engage in a side-by-side spawning embrace, with the male pressing alongside the female and curving his body to align the genital openings. The pair dive together into soft substrate — peat, mud, or detritus — depositing eggs buried several millimetres below the surface with each embrace.
Males are aggressive toward each other and can be aggressive to females outside of spawning readiness, consistent with the territorial behaviour characteristic of many annual killifish (It Rains Fishes). In seasonal pool habitats where adult fish live only for months, competition for reproductive opportunities is intense. The brief, intense adult phase is characteristic of annual killies whose entire reproductive output must occur before the pool dries.
Female Campellolebias dorsimaculatus produce relatively small clutches deposited incrementally over weeks of spawning activity, burying each egg in the soft bottom substrate where it will remain through the dry season.
Breeding
Campellolebias dorsimaculatus is a true annual killifish: its eggs undergo diapause — a period of arrested embryonic development — that allows them to survive the complete desiccation of their natal pool during the dry season. Eggs are buried in the substrate by the spawning pair and remain dormant in the dried peat or mud for weeks to months until rains refill the pool, at which point they hatch within hours to days.
In the aquarium, the annual method is replicated using a peat or coir spawning substrate in a tray or container on the tank bottom. After a spawning period of several weeks, the medium is removed, gently pressed to remove excess water, and stored in a sealed plastic bag at room temperature (approximately 75 °F) for 8–12 weeks — the incubation period cited by It Rains Fishes for this species. The bag is then opened and the peat placed in a shallow container of very soft, slightly acidic water warmed to approximately 75 °F; hatching typically begins within hours of re-wetting. Fry are small but free-swimming immediately at hatch and can be fed microworms, freshly hatched Artemia nauplii, or other appropriately sized live foods from day one. Growth is rapid.
The full life span in the wild is under two years, often considerably less; in captivity, adults maintained in good conditions may live one to two years from hatch (Environmental Inclusion records an approximate lifespan of two years). Experience with the diapause management technique is essential for successful breeding.
In the aquarium
Campellolebias dorsimaculatus is considered a challenging species suitable for experienced killifish keepers. It Rains Fishes rates it as difficult to maintain, and its requirement for live foods and highly specific water chemistry — soft, blackwater conditions at pH 5.0–5.5 — rules out casual community tank placement. A small, species-only or single-pair setup of 5.5–10 US gal with a dark substrate, floating plants or dried leaf litter for cover, and very gentle filtration best replicates the forest-floor pool environment.
Water quality must be maintained with regular small changes, but aggressive filtration and strong currents are inappropriate. The use of RO water reconstituted to very low hardness, acidified with tannins from peat filtration, alder cones, or Indian almond leaves is the standard approach among Atlantic Forest killifish keepers. Temperature should be maintained in the 68–75 °F range to reflect the cooler forest-floor microclimate rather than tropical community tank temperatures.
Because of its Critically Endangered status and restricted wild range, any specimens in the hobby likely represent an important ex-situ reservoir for the species. Killifish societies — particularly the American Killifish Association (AKA) — coordinate the maintenance and exchange of rare annual species to maintain genetic diversity in captive lines. Keepers of this species are encouraged to connect with organised killifish networks and to maintain detailed records of line provenance and breeding success.
Conservation
The IUCN Red List assesses Campellolebias dorsimaculatus as Critically Endangered (CR), with the assessment completed in 2018. The species qualifies under the highest threat categories primarily due to its extremely restricted range — it is known from only a small number of localities within the Ribeira de Iguape River basin in São Paulo state, Brazil — and ongoing decline in extent and quality of its Atlantic Forest habitat.
The Atlantic Forest biome has lost over 85% of its original extent through centuries of agricultural conversion, urbanisation, logging, and infrastructure development. The Ribeira de Iguape valley retains relatively large forest remnants by Atlantic Forest standards, but even intact forest patches are threatened by fragmentation, selective logging, conversion to banana and tea plantations, and drainage modification. For a species entirely dependent on shallow seasonal pools within intact primary forest, the loss or degradation of even small forest patches can eliminate entire local populations.
Campellolebias dorsimaculatus has no known ability to disperse beyond its natal watershed; it cannot colonise new pools across land barriers. Populations at different localities are therefore effectively isolated, and local extinctions are irreversible on any meaningful human timescale. No captive conservation programme specifically targeting this species is publicly documented, though the killifish hobby community plays an informal role in maintaining lines of rare annual killifishes. Formal protection of the remaining forest habitat in the Ribeira de Iguape basin is the most critical conservation action for this species.