Taxonomy & naming
Creagrutus mucipu was described by Richard P. Vari and Andrew S. Harold in their 2001 monograph revising the cis-Andean species of the genus Creagrutus — a landmark work that formally diagnosed 64 species in the genus, 37 of them new to science. The type locality is Colombia, Caquetá department, in the Florencia area of the Río Orteguaza drainage. The valid name, governed by Eschmeyer's Catalog of Fishes, is Creagrutus mucipu Vari & Harold, 2001.
The genus Creagrutus belongs to the family Characidae (order Characiformes) and represents one of the most species-rich radiations of small characins east of the Andes. Some recent molecular works have treated part of this assemblage within a broader circumscription of Stevardiidae, though the higher-level classification remains in flux; the family field here follows Catalog of Fishes usage. Creagrutus species are typically small, drab, silvery characids that are difficult to distinguish without reference to the original descriptions and, in practice, are rarely identified to species in the field or in trade.
Morphology
Creagrutus mucipu is a small, slender-bodied characin with a maximum recorded standard length of 2 in. Like other members of the genus it has the typical Characidae body plan: a compressed, fusiform shape, a relatively small head, a terminal or slightly upturned mouth, and the adipose fin characteristic of the order. Specific diagnostic characters distinguishing C. mucipu from congeners are detailed in the original 2001 description by Vari and Harold, which should be consulted for meristic and morphometric data.
Coloration in life is not documented in available sources for this species; genus members generally display a silvery to pale tan body with a diffuse dark lateral stripe or blotch at the caudal peduncle, and little sexual dichromatism. Scale counts, fin-ray counts, and lateral-line scale numbers are the primary characters used in Creagrutus taxonomy and are set out in the monographic treatment.
Habitat
The type locality of Creagrutus mucipu is the Río Orteguaza drainage in the Caquetá department of Colombia, which is part of the upper Tocantins River system of lowland Amazonia. This region encompasses forested lowland streams typical of the western Amazon basin — clear to lightly tea-stained, often soft and slightly acidic tributaries flowing through primary and secondary tropical forest.
FishBase classifies the species as benthopelagic and tropical, suggesting it inhabits the lower and middle portions of the water column in riverine environments. Specific microhabitat data — substrate type, depth range, water chemistry parameters measured at collection sites — are not detailed in the available sources, and the species remains poorly documented in the field beyond its type-locality record.
Feeding
No specific dietary studies have been published for Creagrutus mucipu. Genus-level information and the ecology of comparable small Amazonian characins suggest an opportunistic insectivore-omnivore diet: small invertebrates including aquatic insect larvae, micro-crustaceans, and terrestrial insects that fall to the surface, with occasional plant material or detritus.
The benthopelagic classification indicates feeding occurs at or near the substrate as well as in the water column. In an aquarium context, small Creagrutus species would be expected to accept prepared micro-pellets and fine flake as well as frozen and live small invertebrates such as Daphnia, Cyclops, and newly hatched brine shrimp — though this species is essentially absent from the hobby and husbandry observations are unavailable.
Mating
No observations of courtship or mating behavior in Creagrutus mucipu have been published. By analogy with other small Amazonian characids of similar ecology, the species is presumed to be an egg-scattering open spawner with no parental care — the typical mode in Characiformes. Males and females in breeding condition are likely to scatter adhesive or semi-adhesive eggs among fine-leaved aquatic plants or substrate debris, with fertilisation occurring externally.
Sexual dimorphism in Creagrutus is generally subtle; females of egg-bearing congeners are often fuller-bodied than males, but reliable external characters are not described for this species in the available literature.
Breeding
Breeding in captivity has not been documented for Creagrutus mucipu, and the species is not established in the aquarium trade. Based on the biology of closely related Amazonian characins, spawning would be expected to follow the egg-scattering pattern typical of the family: adults releasing small numbers of adhesive eggs among fine-leaved plants or spawning mops, with no parental investment. Eggs and fry would need to be removed from adults to prevent predation.
Incubation duration, clutch size, and fry requirements are unknown. Any account of breeding this species in the aquarium would constitute a significant hobby observation and should be documented for publication.
In the aquarium
Creagrutus mucipu is not available in the ornamental fish trade and is not kept in the aquarium hobby to any documented extent. Its small size — under 2.5 in standard length — and presumed peaceful, schooling nature would in principle make it suitable for a species aquarium or a community of similarly sized, non-aggressive small characids, but no husbandry data exist.
For any collector fortunate enough to obtain specimens — through scientific collecting permits or specialist exchanges — the general requirements of small Amazonian stream characins would apply as a starting point: soft to moderately soft, slightly acidic to neutral water, tropical temperatures in the range typical of Colombian lowland streams, subdued lighting, and a heavily planted or botanicals-rich environment with gentle flow. The species should be considered data sparse for aquarium purposes.
Conservation
Creagrutus mucipu is assessed as Data Deficient (DD) on the IUCN Red List, with the assessment completed in November 2018. The Data Deficient listing reflects a genuine lack of population-level information: the species is known primarily from its type-locality collection in the Caquetá region of Colombia, and there is insufficient data to evaluate its range, abundance, or the extent of threats it may face.
The Río Orteguaza drainage lies within a region subject to ongoing deforestation, agricultural expansion, and associated water-quality degradation across the Colombian Amazon. While no targeted threats to C. mucipu are documented, small-stream characins with narrow or poorly sampled ranges are inherently vulnerable to habitat loss. Further collecting and ecological survey work in the Caquetá lowlands would be needed to support any future reassessment of the species' conservation status.