Taxonomy & naming
Creagrutus cerritulus was formally described by André Luís Netto-Ferreira and Richard P. Vari in 2017, in a paper published in Copeia (volume 105, issue 2, pages 368–374). The type locality is the Río Cachiyacu, a tributary of the Río Huallaga in the Amazon basin of Peru. The valid name, as recorded in Eschmeyer's Catalog of Fishes, is Creagrutus cerritulus Netto-Ferreira & Vari, 2017.
The genus Creagrutus belongs to the large and taxonomically complex family Characidae. It encompasses many dozens of species distributed across river systems of Central and South America, with centres of diversity in Andean foothills and Amazonian tributaries. Species in the genus are typically small, stream-associated characids that can be difficult to distinguish from one another without close examination of dentition and internal anatomy.
Morphology
Creagrutus cerritulus reaches a maximum recorded standard length of 2 in, placing it among the smaller members of its genus. The species is distinguished from its congeners by an unusual suite of morphological modifications that the ETYFish Project describes as intense relative to other Creagrutus and more broadly to its subfamily Stevardiinae: the jaws are ventrally displaced, the teeth are compressed and spatulate in form rather than the more typical conical shape seen in many characids, and the swim bladder is reduced.
These characters, taken together, suggest an adaptation to a specialised feeding mode — possibly picking invertebrates or algae from rock surfaces in fast current — though the ecological significance of the jaw and dental modifications has not been described in detail in available sources. The general body form follows the Creagrutus pattern: a laterally compressed, slender to moderately deep fish with the adipose fin present, small scales, and the lateral-line system typical of stream-dwelling characids.
Habitat
The type locality of Creagrutus cerritulus is the Río Cachiyacu, a tributary of the Río Huallaga in the Amazonian department of Peru. FishBase records the species as occurring in moderate to strong currents over substrates of pebbles and rocks — habitat typical of fast-flowing Andean foothill streams in the upper Amazon basin. The water at the type locality was noted as reddish and alkaline in character, an unusual combination suggesting some influence of organic acids alongside a mineral-rich catchment. A minimum recorded temperature of 46 °F has been noted for this locality, consistent with the high-altitude Huallaga drainage where stream temperatures can drop considerably at elevation.
The distribution of Creagrutus cerritulus outside the type locality is not well documented in available sources; the species is known from Peru and the Amazon basin more broadly, but detailed range information is sparse for a recently described taxon.
Feeding
No dedicated feeding study of Creagrutus cerritulus exists in the published literature accessible for this account. The morphological features of the species — ventrally displaced jaws and spatulate, compressed dentition — differ notably from those of generalised omnivorous characids and may indicate a specialised diet, potentially including invertebrates or epilithic material gleaned from rock surfaces in fast current.
Broader observations of Creagrutus species in the wild describe them as small invertebrate predators and opportunistic foragers typical of swift stream habitats in the Neotropics. In an aquarium context, should the species be kept, small live and frozen invertebrate foods together with fine-particulate prepared diets would be the most appropriate approach given what is known of its morphology and genus.
Mating
No field or laboratory observations of mating behaviour in Creagrutus cerritulus have been published in sources available for this account. Like other small, stream-associated characids in the Stevardiinae and broader Characidae, the species almost certainly practises open egg-scattering without parental care, which is the dominant reproductive mode in the group.
In the absence of specific data, any detailed account of courtship or mate choice in this species would be speculative. Data sparse.
Breeding
Breeding biology of Creagrutus cerritulus has not been documented in available sources. By analogy with closely related and ecologically similar characids, spawning is inferred to involve the scattering of adhesive eggs among fine-leaved aquatic vegetation, submerged gravel, or other stream-bed substrate, with no parental guarding of eggs or larvae.
The species has not been established in the ornamental fish trade or in captive breeding programmes to the knowledge available here, so no hobbyist-derived breeding data exist. Data sparse.
In the aquarium
Creagrutus cerritulus is not known to be available in the ornamental fish trade. As a recently described species from remote foothill streams of the Peruvian Amazon, it is not held in hobbyist collections and no aquarium care accounts exist.
For the purposes of general guidance, the species' known ecology — fast current, rocky substrate, cool water down to at least 46 °F at the type locality, alkaline conditions — suggests that keeping it well would require robust water movement, a stable cool temperature range, and a rocky aquascape rather than the planted, warm, soft-water conditions typical of most tetra aquariums. Given the highly modified jaw and dentition, providing appropriate small invertebrate prey or suitable fine prepared foods would be important. This guidance is inferential; direct husbandry experience is absent from the literature.
Conservation
Creagrutus cerritulus has not been assessed by the IUCN Red List as of this writing, and its conservation status is therefore Not Evaluated (NE). As a species described in 2017 from a restricted type locality in the Río Huallaga drainage of Peru, the baseline population data required for a formal assessment — range, population size, trend — are not yet available in published sources.
The Río Huallaga basin in Peru has experienced significant pressure from deforestation, agricultural runoff, and historical contamination associated with coca cultivation and eradication, all of which affect water quality and stream habitat. Whether Creagrutus cerritulus is affected by these pressures, or whether its distribution is wide enough to buffer it against local impacts, cannot be determined from current data. The species warrants survey work to establish its range and abundance before a meaningful IUCN assessment can be made.