Taxonomy & naming
Characidium litorale was described by Rafael P. Leitão and Paulo A. Buckup in 2014, in a paper published in Copeia, as the first species of Characidium recorded from the coastal river basins of the Serra do Mar in southeastern Brazil — the Rio São João, Rio Macaé and Rio Imbé drainages. It belongs to the family Crenuchidae (the South American darters), a group that also contains the sailfin characins Crenuchus and Poecilocharax; within Crenuchidae, Characidium is by far the most speciose genus, comprising small, elongated, bottom-associated fish that perch and dart rather than swim continuously in open water.
The species epithet "litorale" is Latin for "of the coast" or "coastal," referencing the type locality's position in the narrow coastal plain between the Serra do Mar escarpment and the Atlantic, distinguishing it from the many Characidium species described from the Amazon, Paraná and São Francisco basins further inland. The original description notes the species is distinguished from its congeners by a combination of a fully scaled isthmus and hyaline (clear, unpigmented) fins, among other characters. As with many recently described, range-restricted Characidium, taxonomic work on the genus is ongoing and further revision is possible.
Morphology
Characidium litorale is a small fish, with FishBase recording a maximum size of 2 in standard length — solidly within the typical size range for the genus, most of which tops out well under the palm of a hand. The body follows the characteristic Characidium plan: slender and elongate, roughly cylindrical rather than laterally compressed, with a flattened ventral profile that lets the fish rest directly on the substrate. The original description highlights a fully scaled isthmus (the throat region between the gill covers) as part of what separates this species from its closest relatives, along with hyaline, unpigmented fins rather than the barred or spotted fin patterns seen in some other darter characins.
Colouration in Characidium generally runs to cryptic browns, tans and dark blotching along the flank — camouflage suited to a fish that spends its life pressed against sand and gravel rather than schooling in open water — and C. litorale's hyaline fins are consistent with that low-contrast, substrate-blending strategy. Detailed live colouration and any sexual differences beyond general body shape are not covered in the available sources.
Habitat
The type locality is Córrego Aldeia Velha, a small stream in the coastal Serra do Mar region of southeastern Brazil, part of the Rio São João/Rio Macaé/Rio Imbé drainage system that runs off the escarpment directly to the Atlantic rather than into the Amazon or Paraná systems. FishBase describes the habitat as clear water with moderate flow and shallow depth, generally under 19.5 in, over a substrate of sand, clay and gravel — and the species is described as psammophilous, meaning sand-preferring, spending its time perched on or darting over open sandy stretches of streambed rather than hiding in leaf litter or dense cover.
This habitat picture — clear, moderately flowing, shallow coastal streams — puts C. litorale in a different setting from the blackwater and slow floodplain habitats associated with many better-known Amazonian characins, and its restricted, single-region coastal distribution makes it a narrow-range endemic rather than a widespread species.
Feeding
Characidium are micro-predators rather than grazers or omnivorous scavengers, and there is no indication in the available sources that C. litorale departs from this genus-wide pattern. In the wild, darter characins pick tiny aquatic invertebrates — insect larvae, small crustaceans and other micro-invertebrates — from the sand and gravel they perch on, darting a short distance to intercept prey rather than actively cruising for food.
In the aquarium, hobbyist sources covering Characidium as a genus describe a fish that frequently ignores flake food and standard dry foods altogether, doing best on small live and frozen foods such as bloodworm, mosquito larvae, brine shrimp, daphnia and cyclops. Because this diet guidance comes from general Characidium care sources rather than from data specific to C. litorale, it should be treated as a reasonable extrapolation for the genus rather than a confirmed fact about this exact species.
Mating
No courtship or spawning behaviour specific to Characidium litorale is documented in the available sources. Within Crenuchidae broadly, breeding biology differs sharply between the cave- and leaf-spawning sailfin characins (Crenuchus, Poecilocharax), which show brief male parental care, and the true darters of the genus Characidium, which are understood to scatter eggs over the substrate without nest-building or extended parental investment. No species-specific courtship account for C. litorale — such as pairing behaviour, colour change, or a described spawning trigger — was found in the cache; data is sparse here and should not be assumed to mirror the sailfin characins.
Breeding
As a member of the genus Characidium, C. litorale is expected to be an egg-scatterer that releases eggs over sand or fine substrate without building a nest or guarding the clutch — the pattern documented for darter characins generally, in contrast to the cave/leaf-spawning, male-guarding mode seen in the related sailfin characins Crenuchus and Poecilocharax. No confirmed breeding account — captive or wild — specific to Characidium litorale appears in the available sources, so this description should be read as consistent with the genus rather than as observed fact for this species; the species is not documented as being bred in the aquarium hobby to any meaningful extent.
In the aquarium
Characidium litorale stays genuinely small, topping out around 2 in SL, which makes it suitable for a nano or small species setup rather than a large community tank — but its needs are specific. General Characidium care guidance calls for a well-oxygenated aquarium with good filtration and water movement, a sand or fine gravel substrate that lets the fish perch and dart naturally, and company: darter characins are typically recommended in groups of five or more for security, since a solitary or crowded individual is a stressed one.
Because this is a micro-predator that often turns its nose up at flake, keepers should be prepared to offer small live or frozen foods regularly rather than relying on dry staples. Given the species' narrow, single-region coastal Brazilian distribution and its 2014 description, it is unlikely to be a common trade species, and any specimens in the hobby should be assumed wild-collected unless stated otherwise — a point worth weighing for a range-restricted endemic. Water chemistry guidance from general Characidium sources suggests a temperature around 72–79 °F and pH roughly 6.0–7.5, though these figures are extrapolated from genus-level hobby accounts rather than data specific to C. litorale.
Conservation
The IUCN Red List assesses Characidium litorale as Least Concern, as of a 2018 assessment, though the available source material does not include the detailed threat analysis behind that rating. As a narrow-range coastal endemic restricted to a small cluster of Atlantic-slope drainages in the Serra do Mar region of southeastern Brazil — one of the most densely populated and heavily developed parts of the country — the species' habitat sits under real long-term pressure from urbanisation, agriculture and water-quality change even though it is not currently classified as threatened.
There is no indication in the available sources that C. litorale supports any commercial fishery or aquarium trade at scale; it is best understood as a scientifically documented but obscure species whose conservation story rests mainly on the general vulnerability of small-range coastal Brazilian streams rather than on any species-specific pressure identified to date.