Taxonomy & naming
Creagrutus menezesi was described by Richard P. Vari and Andrew S. Harold in 2001 as part of their comprehensive revision of the genus Creagrutus, published in the Smithsonian Contributions to Zoology. That monograph, spanning more than 230 pages, revised the entire genus and described numerous new species from across South America; Vari & Harold 2001 stands as the foundational taxonomic authority for the group. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Van der Laan) accepts Creagrutus menezesi Vari & Harold, 2001 as the valid name.
Creagrutus belongs to the subfamily Stevardiinae within the family Characidae (sensu lato). The genus is extraordinarily species-rich — among the largest in the family — and its members tend to be small, robust-bodied, cryptic in colour, and difficult to distinguish from one another without careful meristic examination. C. menezesi sits within this large, widely distributed assemblage of South American stream and river characins.
Morphology
Creagrutus menezesi reaches a maximum recorded standard length of 3 in, placing it in the middle of the size range for the genus. Like most congeners it is a moderately robust, fusiform fish with the typical characin body plan: a slightly compressed, torpedo-shaped body, a single dorsal fin, an adipose fin, and a forked caudal fin.
Colouration is understated: a silvery to straw-yellow ground colour with diffuse darker markings along the flanks and a lateral stripe or series of spots that is variably distinct depending on condition and preservation. The genus as a whole is notorious for the difficulty of distinguishing species in the field; reliable identification typically requires counts of lateral-line scales, gill rakers, and fin rays, along with measurements of proportional body dimensions. Detailed morphological data for C. menezesi specifically are not widely available in the popular literature, and the original description in Vari & Harold (2001) remains the primary diagnostic source.
Habitat
Creagrutus menezesi is recorded from the Tocantins River basin in central Brazil, with FishBase also listing a tentative distribution in the Rio Branco and Rio Negro systems near the mouth of the Branco — a range consistent with the broad distribution of the genus across northern and central South America. The Tocantins is one of Brazil's great river systems, draining a large swath of the Cerrado and transitional forest zones before discharging into the Pará estuary near Belém.
The species is characterised as benthopelagic, inhabiting the lower and mid-water zones of freshwater streams and rivers. It occupies tropical lowland and sub-upland river habitats, likely favouring moderate-current reaches with structured substrate and aquatic vegetation or woody debris as cover. Water temperatures in the Tocantins basin are warm year-round, broadly in the tropical range consistent with the genus. Specific water chemistry data for the collection localities of C. menezesi are not documented in the available sources.
Feeding
FishBase assigns Creagrutus menezesi a trophic level of 2.3, which places it among the lower-trophic-level consumers — feeding primarily on fine organic material, algae, small invertebrates, and microcrustaceans rather than on larger prey. This profile is consistent with many benthopelagic small characins that exploit the rich invertebrate and detrital resources of river substrate and marginal vegetation.
Detailed dietary studies specific to C. menezesi do not appear in the available literature. By analogy with the genus and with related small Characidae, the natural diet likely includes chironomid larvae, microcrustaceans, small insects, and plant or algal material, foraged close to or along the bottom in moving water. In captivity, small characins of this type generally accept a varied diet of fine granular foods, frozen Daphnia, and small live invertebrates, though C. menezesi is rarely encountered in the hobby.
Mating
No published observations of mating behaviour in Creagrutus menezesi are available. Based on the reproductive biology of the genus and of Characidae more broadly, the species is presumed to be an open-water egg scatterer with no parental care — the ancestral mode in the family.
In congeners and related characins, courtship is typically brief: a male pursues a ripe female through open water or vegetation, and spawning occurs in rapid bursts with eggs scattered over substrate or among plants. Eggs are non-adhesive or weakly adhesive and receive no attention from either parent after release. Sexual dimorphism in Creagrutus is generally subtle, with females often appearing fuller-bodied when gravid.
Breeding
No captive-breeding records for Creagrutus menezesi appear in the hobby or scientific literature. The species is essentially absent from the aquarium trade, so breeding observations from aquarists do not exist in any widely available form.
By extension from the family, breeding would be expected to follow the standard open-spawning characin pattern: eggs scattered in open water or among fine-leaved vegetation, no nest built, no parental care, and fry that are free-swimming within a few days of hatching. Incubation times and fry sizes would depend on water temperature; at tropical temperatures consistent with the Tocantins basin (roughly 75–82 °F), hatching would typically occur within 24–48 hours for most small characins, with fry requiring very fine first foods. These details remain undocumented for this species specifically.
In the aquarium
Creagrutus menezesi is not an established aquarium species and is not commercially available through the ornamental fish trade in any consistent way. Occasional specimens may appear as bycatch in shipments of wild South American fish, but no established husbandry literature exists for this species, and captive populations are not documented.
For aquarists who do encounter it, the general care parameters for small Creagrutus species apply: a tropical freshwater aquarium maintained in the range of 72–79 °F, neutral to slightly acid or alkaline water consistent with Tocantins conditions, efficient filtration, and a diet of small invertebrate foods and fine prepared foods. As a benthopelagic species it would likely appreciate a well-structured tank with substrate cover, plants, and moderate flow. The genus is peaceful and small enough to keep with a wide range of similarly sized, non-aggressive tankmates.
Conservation
Creagrutus menezesi is assessed as Least Concern (LC) on the IUCN Red List, with the evaluation conducted in November 2018. The Least Concern listing reflects a species that does not meet thresholds for a threatened category under current data, but it does not imply that the Tocantins basin faces no pressures — the river system has been significantly altered by hydroelectric development, most notably the Tucuruí Dam, which flooded a large section of the middle Tocantins and transformed the hydrology and habitat of the basin.
The tentative range extension to the Branco and Negro systems, if confirmed, would indicate a broader distribution than a single river basin and would support the Least Concern designation. Data on population trends, specific habitat sensitivity, and responses to hydrological alteration are not available for this species in the published literature. As with many small, cryptic Neotropical characins, its ecology and conservation needs remain poorly studied.