Taxonomy & naming
Creagrutus figueiredoi was formally described by Richard P. Vari and Anthony S. Harold in their 2001 systematic monograph on the genus Creagrutus, a work that reviewed 56 species east of the Andes and named 37 new ones, bringing the known genus total to 64 species at the time of publication. The paper was published as a Smithsonian Contributions to Zoology monograph, and type material is held at the National Museum of Natural History (USNM); paratypes include adult specimens collected from the Minaçu and Colinas do Sul region of the state of Goiás, in the upper Tocantins drainage.
Creagrutus belongs to the subfamily Stevardiinae of the family Characidae, a hyperdiverse Neotropical grouping. The genus is characterised by a relatively slender body, a subterminal to terminal mouth, and a suite of osteological and squamation characters that set it apart from the broadly similar Bryconamericus and allied genera. Valid name per Eschmeyer's Catalog of Fishes: Creagrutus figueiredoi Vari & Harold, 2001. Because the species was described in Creagrutus and remains there, no parenthetical authority is used.
Morphology
Creagrutus figueiredoi is a small characid; FishBase records a maximum standard length of 2.5 in SL for male or unsexed specimens, which is representative of the genus as a whole. Paratype material includes an adult male of 2 in SL and an adult female of 2 in SL, indicating that females may slightly exceed males in length — a pattern common in small characids.
The body form is typical for Creagrutus: moderately elongate and laterally compressed, with a blunt snout, moderately large eye, and a subterminal mouth directed slightly downward, consistent with a benthopelagic lifestyle. Coloration in life has not been described in detail in accessible sources; preserved specimens of most Creagrutus species show a pale to silvery lateral stripe bordered above by a darker band along the flank, with a dark mid-lateral stripe or caudal spot — a generic pattern broadly shared across the genus. The adipose fin is present, as is the small fleshy axillary process at the base of the pelvic fin seen in many stevardiine characids.
Habitat
The species is recorded from the upper Tocantins River drainage, encompassing both the upper Tocantins proper and the Araguaia River basin in central Brazil. The Tocantins–Araguaia system drains the central Brazilian plateau (Planalto Central) through the states of Goiás, Tocantins, and adjacent areas before flowing north to the Pará estuary. Type localities in the Minaçu and Colinas do Sul region of Goiás lie in the upper reaches of the drainage, where rivers are typically fast-flowing, clear to lightly tannic, and well oxygenated over rocky or sandy substrates.
FishBase classifies C. figueiredoi as a freshwater benthopelagic tropical species, consistent with the typical Creagrutus microhabitat of stream margins and riffles in forested or open-savanna headwaters. Water temperatures in the upper Tocantins at these elevations are warm year-round, broadly in the tropical range. No detailed habitat survey data for this species specifically are available in accessible sources.
Feeding
No dietary study specific to Creagrutus figueiredoi has been published in accessible sources. Creagrutus species generally are considered opportunistic omnivores or micropredators, consuming small aquatic invertebrates — insect larvae, microcrustaceans, and similar items — along with terrestrial insects that fall to the surface and incidental plant material. The subterminal, slightly downward-directed mouth of the genus is well suited to picking food from the substrate or water column near the bottom.
In captivity, analogous small Neotropical characids accept fine flake and micropellet foods readily, along with small live or frozen invertebrates such as Daphnia, cyclops, and baby brine shrimp. There is no evidence that C. figueiredoi is nutritionally specialised or difficult to feed.
Mating
No courtship or mating behaviour has been described for Creagrutus figueiredoi specifically. Based on the biology of closely related characids in the subfamily Stevardiinae and the broader family Characidae, the species is expected to be an egg-scatterer that spawns among fine-leaved vegetation or over the substrate without forming pair bonds. Males in many small characids develop breeding tubercles or subtle colour intensification during the spawning season, and some stevardiine species are known to show mild internal fertilisation or sperm storage, though these traits are not confirmed for Creagrutus figueiredoi.
Spawning is likely seasonal in the wild, tied to the wet-season hydrology of the central Brazilian plateau when water levels, temperature, and food availability shift. In aquaria, small characids of this type typically spawn when water chemistry is stable, the fish are well conditioned, and a slight drop in water temperature mimics the onset of the wet season.
Breeding
Creagrutus figueiredoi has not been bred in the hobby to any documented degree, and no captive breeding reports appear in accessible sources. By analogy with other small Neotropical characids, the mode is expected to be open egg-scattering among fine-leaved plants or spawning mops, with adhesive or semi-adhesive eggs, no parental care, and adults that will consume eggs if not removed.
Incubation times and fry development data are not available for this species. Aquarists attempting to spawn closely related small Creagrutus species have used soft, slightly acidic to neutral water, fine-leaved plants such as Java moss or synthetic mops, and removal of adults immediately after spawning. Fry would be expected to require very fine first foods — infusoria, rotifers, or commercial liquid fry food — before accepting newly hatched brine shrimp nauplii.
In the aquarium
Creagrutus figueiredoi is rarely if ever found in the aquarium trade; it has not entered hobby commerce in any meaningful way and is kept only by specialist collectors of Neotropical characids. As a small, benthopelagic schooling characid it would, in principle, be suitable for a species tank or a biotope aquarium replicating central Brazilian headwater streams — clear, well-oxygenated water with some current, a sandy or fine-gravel substrate, scattered leaf litter or smooth stones, and minimal decoration.
Based on its wild habitat, water parameters in the range of 73–77 °F, neutral to slightly acidic to slightly alkaline pH, and low to moderate hardness would be appropriate. It should be kept in a group of at least six to express natural schooling behaviour and reduce individual stress. Tankmates, if any, should be small, peaceful Neotropical species of similar size. The lack of any established hobbyist experience with this species means that practical husbandry details remain largely inferred from genus-level knowledge.
Conservation
Creagrutus figueiredoi was assessed as Least Concern (LC) on the IUCN Red List, with the assessment dated 7 November 2018. The Least Concern designation reflects a distribution across the upper Tocantins and Araguaia River basins — a large and still-functioning drainage within Brazil's cerrado and transition-forest biomes — without evidence of a rapid enough population decline to warrant a threatened category.
That said, the Tocantins drainage has been significantly altered by hydroelectric development, most notably the Tucuruí Dam and subsequent reservoir construction, and the cerrado biome more broadly is one of the world's most threatened biodiversity hotspots, subject to ongoing agricultural conversion and habitat fragmentation. Headwater characids dependent on clear, well-oxygenated streams are inherently vulnerable to catchment disturbance. The current Least Concern status should be understood as reflecting available data at the time of assessment rather than an absence of future risk.