Taxonomy & naming
Campellolebias chrysolineatus was described by Wilson J. E. M. Costa and Ricardo Lazara in 1994. It is placed in the family Rivulidae (South American annual killifishes) within the order Cyprinodontiformes. The genus Campellolebias is a small, cohesive assemblage of seasonal killies from coastal Atlantic Forest drainages in southern Brazil, sharing a suite of morphological features — including the pseudogonopodium used in internal insemination — that distinguish them from the broader annual killi fauna of South America. Eschmeyer's Catalog of Fishes is the authority for the valid combination Campellolebias chrysolineatus Costa & Lazara, 1994.
A 2025 review published in Zoologischer Anzeiger provides a comprehensive treatment of the Campellolebias genus, confirming the placement of C. chrysolineatus and consolidating knowledge of the genus's distribution and conservation status. All recognised species within the genus are assessed as Critically Endangered, underlining the vulnerability of a group tied almost exclusively to temporary Atlantic Forest pools in a heavily modified landscape.
Morphology
Campellolebias chrysolineatus is a small fish reaching approximately 2 in standard length (SL), typical of the compact build common to annual killies that must complete their life cycle within a single wet season. The specific epithet chrysolineatus derives from the Greek chrysos (gold) and the Latin lineatus (lined or streaked), and refers directly to the golden spots or streaks running along the scales on the flanks — a diagnostic feature distinguishing this species from its congeners and a striking character visible in well-lit, healthy males in breeding condition.
As in other Campellolebias, males are more intensely coloured than females and carry the pseudogonopodium — a modification of the anal fin that facilitates internal insemination, an unusual trait within the annual killifish radiation. Females are plainer, with more subdued colouration and an enlarged, rounded abdomen when gravid. The body form is fusiform and slightly dorso-ventrally compressed, well-suited for moving through and diving into soft substrate during spawning.
Habitat
This species inhabits small temporary pools and low-lying seasonal wetlands within the Atlantic Forest biome of southern Brazil. Type localities documented by the American Killifish Association include Maire Paira and Araquari in the state of Santa Catarina, as well as Ilha de São Francisco and Joinville — all within a geographically restricted coastal belt. These pools form during the rainy season and dry out completely in the dry months, a hydrological cycle that is both the engine of the species' annual reproductive strategy and the source of its vulnerability to habitat alteration.
The Atlantic Forest pools occupied by C. chrysolineatus are typically shallow, soft-bottomed, and rich in leaf litter and organic detritus — the substrate into which spawning pairs submerge to deposit eggs. Water temperatures and chemistry in such seasonal pools fluctuate seasonally; the surrounding forest provides shade and inputs of leaf litter that acidify and darken the water in the wet season. Precise water-chemistry parameters for this species are not extensively published, but conditions in the Atlantic Forest coastal zone are generally soft and mildly to moderately acidic.
Feeding
Like other small annual killies, Campellolebias chrysolineatus is a micro-predator, feeding on small invertebrates, aquatic insect larvae, microcrustaceans, worms, and other zooplankton encountered in its temporary-pool habitat. The fast-paced life history of an annual species — growing rapidly from hatching to reproductive maturity within a single wet season — demands efficient and opportunistic foraging.
In the aquarium, the species accepts live and frozen small foods readily: micro-worms, white worms, Daphnia, Artemia nauplii, and small chironomid larvae. Variety in diet supports condition and promotes the vivid colouration that makes males of this genus attractive. Prepared micropellets may be accepted by established individuals but should be supplemented with live or frozen items for best results.
Mating
Campellolebias chrysolineatus is an annual killifish that employs internal insemination via the male's pseudogonopodium — a modification of the anal fin rays that transfers sperm directly to the female, an exceptional feature within the otherwise externally fertilising Rivulidae. This mechanism is confirmed across the Campellolebias genus by the 2025 Zoologischer Anzeiger study.
Courtship in South American annual killies typically involves intense male display, with the male positioning himself alongside or above the female and spreading his fins to present his best colouration. The pair then engages in the spawning dive characteristic of annual killies: both fish submerge into the soft substrate using what has been described as a 'coiled retrorse motion', with the male coiling around the female and driving backward and upward at roughly a 45° angle before copulation. Eggs are deposited deep in the substrate during this manoeuvre, buried well below the surface where they are protected from the extreme temperature fluctuations and desiccation of the dry season.
Breeding
The breeding biology of C. chrysolineatus follows the annual killifish model: eggs are buried in soft substrate (peat, mud, or detritus at the pool bottom) during the wet season, and the adults typically die when the pool dries. The drought-resistant eggs enter diapause — a state of arrested development — that allows them to survive the dry season buried in dry or damp substrate. FishBase records a diapause period of approximately 120 days (four months) for this species, after which the eggs hatch when the rains return and the pool refills.
Research on annual killifish eggs documents that diapause is not a single arrested state but a series of developmental phases; eggs may hatch at different points depending on environmental cues, and not all eggs in a clutch will necessarily complete every diapause phase before hatching. In the hobby, spawning is conducted on peat moss or coconut coir: after the spawning period the medium is gently squeezed to remove excess water, sealed in a plastic bag, labelled with the date, and stored in a warm dark location for approximately 90–120 days before being re-wetted to trigger hatching. Hatching fry are minute and require infusoria or commercial microfry foods initially, graduating rapidly to Artemia nauplii and micro-worms as growth is fast in warm water.
In the aquarium
Campellolebias chrysolineatus is a speciality fish suited to experienced killifish keepers rather than general community aquarists. A small, heavily planted or peat-filtered species tank is ideal — a tank of around 10–15 US gal is ample for a pair or small group, with a soft, fine-grained substrate layer of peat or coconut coir for spawning. A tight-fitting lid is important, as killies are capable jumpers.
Water conditions should reflect the Atlantic Forest origin: soft, slightly acidic water (pH roughly 5.5–7.0) with temperatures in the range appropriate for subtropical southern Brazil — cooler than the tropical killies of equatorial South America. Dim lighting, tannin-stained water, and a covering of floating plants or surface shade create conditions that encourage natural behaviour and bring out male colouration. The pseudogonopodium-mediated spawning means the hobbyist will not see the external egg-scattering of many other killies; instead, pairs should be watched for the characteristic diving dive into the substrate.
This species is poorly represented in the mainstream hobby, in part because of its rarity in the wild and its Critically Endangered status. It circulates primarily through specialist killifish clubs and the American Killifish Association's fish-distribution programs, where maintaining genetically diverse captive populations serves a genuine conservation function alongside the hobbyist interest.
Conservation
The IUCN Red List assesses Campellolebias chrysolineatus as Critically Endangered (CR), assessed in 2018, a status that reflects the extreme narrowness of its range and the severity of threats to the Atlantic Forest coastal habitats it depends on. The 2025 Zoologischer Anzeiger revision of the genus confirms that all Campellolebias species share this status, underscoring how the group as a whole is imperilled by the same landscape-level forces.
The primary driver of decline is habitat loss and fragmentation within the Atlantic Forest — one of the world's biodiversity hotspots and one of its most threatened biomes, now reduced to a fraction of its original extent. Residential development along the Santa Catarina coast and in the Joinville and Araquari areas has directly destroyed and degraded the low-lying seasonal pools that C. chrysolineatus requires. The species' type localities lie in a region under intense development pressure, and the small, isolated nature of temporary-pool habitats makes them particularly susceptible to drainage, infill, and hydrological disruption from surrounding land use.
The very qualities that define an annual killifish — dependence on temporary pools that dry completely each year — make species like C. chrysolineatus acutely vulnerable to any alteration of the local hydrological cycle. Groundwater extraction, channel modification, and the conversion of floodplain areas eliminate the ephemeral pools on which the entire life cycle turns. Given the species' restricted endemic range and the acceleration of Atlantic Forest coastal development, captive maintenance in specialist killifish collections represents a meaningful complement to in-situ conservation efforts.