Taxonomy & naming
Characidium kamakan was described by Angela Zanata and Josiane Camelier in 2015, placing it in the family Crenuchidae — the South American darters and sailfin characins — within the order Characiformes. The genus Characidium is a large assemblage of small, elongate, bottom-associated characins found throughout South American stream systems, distinguished from the shoaling, mid-water tetras of Characidae and from the cave- and leaf-spawning sailfin characins (Crenuchus, Poecilocharax) of the same family by their habit of perching and darting along the substrate rather than swimming continuously.
The species epithet "kamakan" references the Kamakã, an indigenous people historically associated with the Bahia region where the species was collected, following a common convention in Brazilian ichthyology of honouring local indigenous groups or place names in new species descriptions. The type locality lies in the rios Água Preta and Panelão, tributaries of the lower rio Pardo basin, and the holotype measured 2 in standard length (roughly 2 in). As with many recently described Characidium, the genus remains taxonomically active, and species boundaries within the group continue to be refined through further fieldwork and description.
Morphology
Characidium kamakan is a small, slender, elongate characin reaching only about 2 in, consistent with the compact, torpedo-like body plan typical of the genus and suited to holding position against current on a stony streambed. The original description notes a distinctive colour pattern: the scales along the flanks carry dark borders that combine into short vertical bars, and the caudal fin bears a bold black blotch shaped like the numeral "3" — a field mark useful for separating it from superficially similar congeners in the same river system.
As in other darter characins, the body is only lightly compressed and the fins are relatively unadorned compared with the showier sailfin characins in the same family; the emphasis is on a cryptic, substrate-matching pattern rather than bright display colouration, fitting a fish that relies on stillness and quick, short darts rather than open swimming to avoid predators.
Habitat
The species is known from fast-flowing streams with medium-to-large stone substrate in the rios Água Preta and Panelão, tributaries of the lower rio Pardo basin in Bahia State, eastern Brazil. This places it within the Atlantic Forest (Mata Atlântica) ecoregion of coastal northeastern Brazil, a drainage system distinct from the Amazon, Orinoco and Paraná basins that host most of the continent's better-known characins, and the available data point to a range restricted to this river system rather than a broad South American distribution.
Within these streams, Characidium kamakan occupies riffle-like stretches with rocky bottoms and moving water, where it perches on and among stones — a habitat and behaviour typical of the genus generally. Detailed water-chemistry data specific to the type locality were not captured in available sources; the temperature and pH figures given here follow general husbandry accounts for Characidium as a genus rather than site-specific measurements for this species.
Feeding
Characidium kamakan is presumed, in line with the genus generally, to be a micro-predator taking small aquatic invertebrates, insect larvae and other tiny prey items picked from the stony substrate and surrounding current, rather than an algae- or plant-based feeder. No species-specific dietary study is available in the sources consulted.
In the aquarium, Characidium species as a group are documented micro-predators on small invertebrates, chironomid midge larvae and other fly larvae, and they often ignore dry flake food entirely, doing best on frozen bloodworm and small live foods such as microworm and baby brine shrimp.
Mating
No species-specific courtship account for Characidium kamakan was found in the sources consulted. In Characidium generally, spawning is not associated with the elaborate cave- or leaf-guarding courtship seen in the related sailfin characins (Crenuchus, Poecilocharax); pairs instead come together over open substrate. Given the absence of direct observation for this species, the details here should be treated as inferred from genus-level accounts rather than confirmed for C. kamakan specifically.
Breeding
Characidium as a genus are egg-scatterers over the substrate rather than nest-guarders or mouthbrooders, and general aquarium accounts for the genus describe successful breeding in soft, acidic water among fine-leaved plants such as Java moss, with males showing some parental attendance of the clutch in at least some species. No breeding account specific to Characidium kamakan was located, and given how rarely this species is reported in the aquarium trade, it should be considered essentially unbred in captivity at present — the mode described here is a genus-level pattern, not a confirmed observation of this species.
In the aquarium
Characidium kamakan is rarely seen in the aquarium trade, and hobbyist experience with the species specifically is minimal to nonexistent. Prospective keepers should look to general Characidium husbandry as a starting point: a modest nano-to-small aquarium with a sandy or fine-gravel substrate, smooth stones, moderate water flow and open swimming space at the bottom, since these are stream-bed darters rather than open-water shoalers. Water in the 72–79 °F range, slightly acidic to neutral (roughly pH 6.0–7.5), suits the genus generally, though site-specific data for this species were not available.
As micro-predators, Characidium often refuse flake and need frozen bloodworm or small live foods offered directly; they are generally peaceful toward similarly sized tankmates but can be predatory toward very small fish or fry. Given its narrow known range and rarity in the hobby, any specimens encountered in trade should be treated as wild-collected rather than captive-bred stock.
Conservation
Characidium kamakan has not been evaluated by the IUCN Red List; no assessment for the species was found. Its status is consistent with many recently described, geographically restricted South American characins that have not yet been through a formal Red List assessment.
The species is known only from a small area of the lower rio Pardo basin within the Atlantic Forest domain of Bahia State — one of the most heavily deforested and fragmented ecoregions in Brazil, where stream habitat loss, sedimentation and water-quality degradation are well-documented pressures on freshwater fish generally. Without a formal assessment or population data specific to C. kamakan, its conservation status should be treated as data-sparse rather than assumed secure.