Taxonomy & naming
Characidium tatama was formally described in 2020 by Agudelo-Zamora, Tavera, Murillo and Ortega-Lara in the Journal of Fish Biology, based on a holotype (IMCN 8925) collected on 9 September 2018 from the río Ingará, a tributary in the San José Del Palmar area of Chocó department, Colombia (04°55'13.39"N, 76°12'21.48"W). It belongs to the family Crenuchidae — the South American darters, which also contains the blackwater sailfin genera Crenuchus and Poecilocharax — within the order Characiformes, placing it well outside Serrasalmidae, the family that holds the true piranhas and pacus covered elsewhere in this section.
The species epithet honours Tatamá, the Colombian national park associated with the Chocó headwaters where the species and its relatives occur. The authors distinguished C. tatama from congeners by a combination of meristic and morphological characters, including a fully scaled lateral line of 32–33 pored scales, an unscaled isthmus, free branchiostegal rays and a distinctive swim-bladder shape. As with many recently described Characidium, identification rests on these fine anatomical details rather than obvious external colour pattern, and the genus as a whole remains taxonomically active, with new species still being split out of what were once broadly defined, wide-ranging "forms."
Morphology
Characidium tatama is a small fish even by darter-characin standards: the holotype measured 1.5 in standard length, and the original description notes that the largest known specimens do not exceed 2 in SL. The body follows the typical Characidium plan — elongate and only moderately compressed, with a flattened ventral profile and a subterminal mouth suited to picking at the substrate rather than midwater feeding, features shared with unrelated stream darters worldwide through convergent evolution rather than common ancestry.
Diagnostic characters cited in the description include the scale count along the lateral line, the absence of scales on the isthmus, free (unattached) branchiostegal rays, and swim-bladder morphology — details visible mainly under a microscope rather than in the aquarium. Like other Crenuchidae, C. tatama likely shows the genus's characteristic resting posture, propped on its paired fins against the substrate between short darting movements, though the description itself is a taxonomic paper and does not detail live colouration or behaviour in depth.
Habitat
The species is endemic to the Chocó biogeographic region of western Colombia, currently documented from tributaries of the upper San Juan and Calima rivers. The type locality, the río Ingará, is described as a torrential river with a rocky substrate, abundant riparian forest cover, and relatively few pools or backwaters — fast, well-oxygenated, structurally complex water typical of foothill streams draining the Chocó's exceptionally wet forests.
This is a narrow-range endemic in the strictest sense: the known distribution spans an area of less than 12 mi² across only a handful of localities, which is itself the basis for its conservation status (see "Conservation"). No detailed water-chemistry readings (temperature, pH) were captured for the type locality in the sources available for this account; readers should treat any specific numbers for this species as provisional rather than assume the wider Chocó/Neotropical norms without direct confirmation.
Feeding
Characidium tatama is a micro-predator, consistent with the genus as a whole: the original description notes a diet of aquatic insects and their larvae, gleaned from the rocky substrate and current-swept surfaces of its torrential home stream rather than hunted in open water. This puts it in the same ecological role as North American darters and European bullheads — a small, opportunistic invertebrate feeder working the stream bed.
In the aquarium, darter characins of this genus are reported to largely ignore dry foods and do best on small live or frozen invertebrate fare — bloodworm, brine shrimp, Daphnia and cyclops — offered where a bottom-oriented fish can reach it before faster tankmates clear it out. There is no aquarium-specific feeding data published for C. tatama itself, so this guidance is extrapolated from the broader genus and should be treated as a starting point rather than a confirmed protocol for this particular species.
Mating
No courtship or spawning behaviour has been documented for Characidium tatama specifically — the species is known only from its original taxonomic description and a handful of collection records, not from aquarium or field breeding observations. Data are sparse here, and it would be irresponsible to invent detail this species' own literature does not support.
What can be said comes from the genus and family: Crenuchidae as a group are not open-water broadcast spawners. The sailfin genera Crenuchus and Poecilocharax are known cave- or leaf-spawners with brief male care of the clutch, while Characidium species that have been observed breeding are typically egg-scatterers over fine substrate rather than nest-guarders. Given the rocky, current-swept habitat of C. tatama, egg-scattering into gravel interstices — a mode reported for other Characidium in the hobby literature — is the more plausible pattern, but this has not been confirmed for this species and should not be presented as established fact.
Breeding
Characidium tatama has not been reported bred in the aquarium, and there is no dedicated aquaculture or hobbyist breeding record for this species in the sources consulted for this account. This is unsurprising for a fish described only in 2020 from a narrow, hard-to-access Colombian range and not established in the trade.
For context, other Characidium kept in the hobby are reported as substrate egg-scatterers: a conditioned pair spawns over fine gravel or leaf litter, the roughly 150 adhesive eggs receive no parental care once laid, and hatching follows in 30–40 hours at warm tropical temperatures. Whether C. tatama follows this same pattern is a reasonable inference from its relatives rather than a documented fact, and prospective keepers should treat it as an open question rather than a settled breeding protocol.
In the aquarium
Characidium tatama is not established in the aquarium trade, and given its Vulnerable status and extremely restricted range, it should not be treated as a target for wild collection. The entry here is included for completeness of the genus rather than as a practical care guide for a fish hobbyists are likely to encounter.
Where Characidium species do appear in the trade, the genus is kept as small, active bottom-dwellers rather than midwater shoalers — the common care notes call for a well-oxygenated, current-swept tank with a rocky or coarse-sand substrate, driftwood and plants for cover, and tropical-to-subtropical, slightly acidic to neutral water. They are not aggressive and do best with similarly modest, peaceful tankmates that will not out-compete a slow-feeding, insectivorous bottom fish. None of this is confirmed for C. tatama specifically; it is offered as the genus-level baseline should this or a similar Chocó darter ever become available.
Conservation
The IUCN Red List assesses Characidium tatama as Vulnerable (VU) under criterion D2, reflecting a population confined to fewer than five known localities across an area of less than 12 mi² — the two tributary systems of the San Juan and Calima rivers in Colombia's Chocó region. The assessment identifies accelerated deforestation, including within Colombian national parks, as the principal threat to the watersheds the species depends on.
As a single-region endemic with no known aquarium trade presence, C. tatama's conservation outlook rests almost entirely on habitat protection in the Chocó biogeographic region — one of the wettest and most biologically distinctive areas in the Neotropics, and one under sustained pressure from logging and land conversion. There is no farmed or captive-bred population to buffer wild numbers, which makes habitat integrity in these few Colombian streams the species' only real safeguard.