Taxonomy & naming
Creagrutus guanes was formally described by Torres-Mejia and Vari in 2005, in a paper published in Copeia (volume 2005, issue 4) presenting new species of Creagrutus from Colombia. The type locality is in the Río Fonce basin, a tributary system within the greater Río Magdalena drainage of Colombia. Eschmeyer's Catalog of Fishes is the governing authority for the valid name, which stands as Creagrutus guanes Torres-Mejia & Vari, 2005.
The genus Creagrutus belongs to the family Characidae and is one of the most species-rich genera of Neotropical characiforms, distributed broadly across South American river basins from Venezuela and Colombia to Bolivia and Brazil. Species within the genus are distinguished chiefly by morphometric and meristic characters — body proportions, scale counts, fin-ray counts, and osteological features — since external colouration is often uninformative and convergent. The 2005 paper distinguished C. guanes from congeners on the basis of a suite of such characters, and flagged one unique trait: it is the first Creagrutus recorded with breeding tubercles bearing keratinized caps, a feature otherwise unknown in the genus at the time of description.
Morphology
Creagrutus guanes is a small, slender-to-moderately-built characid reaching a maximum recorded standard length of 3 in. Like other members of the genus, it carries the typical characiform body plan: a laterally compressed, fusiform body; a complete lateral line; a small adipose fin between the dorsal and caudal fins; and a relatively large eye set in a blunt snout. The overall coloration of preserved and live specimens in this genus tends toward silvery to pale yellowish-brown, often with a darker lateral stripe or mid-body band, though pigmentation details for C. guanes specifically are not extensively documented in available sources.
The species' most remarked-upon morphological feature is the presence of breeding tubercles with keratinized caps on reproductively active individuals — the first such condition recorded for Creagrutus. Breeding tubercles are small, hardened projections on the scales or head that appear in spawning condition; the keratinized cap is an additional specialization whose functional significance is not fully understood. Otherwise, the species is diagnosed by the combination of morphometric proportions and meristic counts detailed in the original description.
Habitat
Creagrutus guanes is known from the Río Fonce drainage within the Río Magdalena basin, Colombia — an Andean and sub-Andean river system draining through the Santander and Boyacá departments. The Río Magdalena is Colombia's principal river, running through the inter-Andean valley between the Cordillera Central and the Cordillera Oriental. The Río Fonce and its tributaries flow through a landscape that historically supported the dry and transitional forests of the Chicamocha and middle-Magdalena valleys, portions of which are designated as Key Biodiversity Areas.
FishBase records the species as a freshwater, pelagic, tropical fish, consistent with the stream and river habitats typical of Creagrutus across the genus's range. Specific water-chemistry data for the Río Fonce populations of C. guanes are not documented in the sources available; Andean tributaries of the Magdalena basin are typically clear to moderately turbid with moderate conductivity and temperatures reflecting their elevation. The species shares its drainage with a diverse endemic ichthyofauna, and the Chicamocha–Fonce valley system has been identified as a center of endemism for freshwater fishes.
Feeding
No detailed dietary study of Creagrutus guanes has been published in the available literature. Genus-level feeding ecology in Creagrutus, as documented for related species, is generally that of a small, opportunistic omnivore taking small invertebrates, algae, detritus, and organic material from the water column and benthos — consistent with the pelagic habitat designation recorded for C. guanes on FishBase.
In the aquarium, congeners and close relatives of similar size are typically offered small live and frozen invertebrates — Daphnia, brine shrimp, small bloodworm — alongside quality micro-pellets and fine flake, with plant-derived foods supplementing the diet. Given the limited specific data for this species, aquarists keeping it should follow husbandry norms for small Neotropical characids: varied diet, small frequent feedings, and avoidance of large or aggressive food items.
Mating
Reproductive biology specific to Creagrutus guanes in the wild has not been described in available sources beyond the discovery of breeding tubercles with keratinized caps, which confirms that tubercle-bearing individuals exist and implies seasonal or condition-dependent reproductive cycling. Breeding tubercles in characiforms are most often associated with males and appear during spawning condition, suggesting a role in tactile courtship or spawning contact, though their precise function in Creagrutus remains unclear.
By analogy with other small characids, courtship in C. guanes likely involves males pursuing or displaying to females in open water, with egg scattering as the spawning mode. The keratinized-cap tubercles may play a role in physical contact during the spawning act, as has been proposed for similar structures in other characiform families, but this is inference rather than documented observation.
Breeding
Captive breeding of Creagrutus guanes has not been documented in the hobbyist or scientific literature available. Based on family-level and genus-level biology, the species is expected to be an egg-scattering open-water spawner producing small, non-adhesive or lightly adhesive eggs among fine-leaved vegetation or in open current, with no parental care — the reproductive strategy typical of small, stream-dwelling Neotropical characids.
Should the species become available to aquarists, breeding protocol modeled on related Creagrutus and small characid congeners would be a reasonable starting point: condition adults on varied live and frozen foods, provide a separate spawning tank with fine-leaved plants or synthetic spawning mops, remove adults after spawning to prevent egg predation, and raise fry on fine foods starting with infusoria or commercial micro-fry foods before advancing to newly hatched brine shrimp. Specific incubation times and fry-rearing details are not documented for this species.
In the aquarium
Creagrutus guanes is not an established aquarium fish and is rarely if ever available in the ornamental trade. It is a small stream characid from Andean Colombia, and like most members of its genus it lacks the vivid coloration or special behaviors that drive hobby demand; most Creagrutus species are known primarily from ichthyological collections rather than aquaria.
Should specimens be kept, an aquarium approximating the clean, well-oxygenated, moderate-flow conditions of Andean tributary streams would be appropriate: soft to moderately hard water, temperatures in the range typical of mid-elevation Colombian streams, efficient filtration, and subdued to moderate lighting with plants or cover. A peaceful, small-fish community or species tank would suit the genus's disposition. Because reliable husbandry data for C. guanes specifically are absent, aquarists should consult accounts of related Creagrutus species and general small-characid care as a baseline.
Conservation
Creagrutus guanes is assessed as Least Concern (LC) on the IUCN Red List, with a 2025 assessment confirming that status. The species is associated with the Chicamocha River Valley region of Colombia, an area noted in the Key Biodiversity Areas database for its dry-forest biodiversity and freshwater endemic species, suggesting that while the species itself is not considered threatened, its broader ecosystem faces ongoing pressures from agricultural conversion, water extraction, and altered hydrology typical of inter-Andean Colombian valleys.
The Río Magdalena drainage as a whole supports high freshwater fish diversity and endemism but has experienced substantial habitat modification. For C. guanes specifically, the Least Concern listing implies that currently known population extent and abundance do not meet threatened-category thresholds, but baseline data for most small, range-restricted characids in Colombia are limited, and range-wide surveys are not regularly repeated. Maintaining watershed integrity in the Río Fonce and associated Andean tributaries — through land-use management, water quality protection, and limitation of extractive pressures — is the most relevant conservation measure for this and the many other endemic fishes of the Magdalena basin.