Taxonomy & naming
Chaetostoma sacramento was formally described by Meza-Vargas, Ramirez, and Lujan in 2024 in the journal Zoosystematics and Evolution (volume 100, issue 4, pages 1387–1400; DOI: 10.3897/zse.100.118522). It is one of only three Chaetostoma known from the Ucayali drainage, alongside C. lineopunctatum and C. loborhynchos. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Chaetostoma sacramento.
The species had attracted attention in the aquarium hobby well before its formal description. Seidel (2011) noted it as an undescribed taxon in the ornamental fish literature and assigned three provisional L-numbers — L455, L456, and L457 — reflecting the high colour-pattern variability seen across individuals from different collection points within the Pampa de Sacramento region. An earlier molecular phylogenetic study (Lujan et al. 2015b) referenced the taxon as 'Chaetostoma sp. nov. Ucayali'. Phylogenetic analysis using the Meza-Vargas et al. (2022) dataset places C. sacramento as sister to C. breve.
The holotype (MUSM 72045, 2.5 in SL) was collected from the Yamino River, a tributary of the Aguaytía River, Peru. Additional material is known from the Pisqui and Palcazu Rivers, all within the Pampa de Sacramento region of the Ucayali drainage.
Morphology
Adults reach approximately 3 in standard length (SL), placing C. sacramento among the smaller members of its genus. The body form is the typical Chaetostoma profile: strongly dorsoventrally flattened, covered in articulated bony scutes, with a broad depressed head and a ventrally positioned sucking disc used to maintain position on smooth rock surfaces in current.
The most striking diagnostic feature is the colour pattern: distinct white, variably-shaped spots or vermiculations, ranging from roughly half to twice the diameter of the nostril, scattered across a grey-to-brown background on the head. This white-on-dark arrangement is unusual among Peruvian Chaetostoma, where most species instead carry black or dark spots on a lighter ground — C. trimaculineum being one well-known example of the more typical pattern. The variability in spot shape and density across individuals from different river systems within the Pampa de Sacramento likely accounts for the three separate provisional L-numbers assigned in the trade.
Additional diagnostic characters include: a fully formed adipose fin (versus rudimentary in C. anomalum); a uniformly brown adipose fin lacking a black spot (separating it from C. dorsale); golden spots on the dorsal-fin rays rather than light banding (versus C. leucomelas); eight branched dorsal-fin rays (versus nine in C. microps); curved rather than straight cheek odontodes (versus C. nudirostre); two predorsal plates (versus three in C. palmeri); an excrescence present; and pelvic-fin insertion positioned slightly posterior to the dorsal-fin insertion. Males develop interopercular odontodes during the reproductive season.
Habitat
Chaetostoma sacramento is known from the Aguaytía, Pisqui, and Palcazu Rivers — all tributaries draining through or around the Pampa de Sacramento, a subandean plain in central Peru between the Huallaga and Ucayali Rivers, bounded approximately by the Pisqui River to the north and the Palcazu River to the south and straddling Huánuco and Ucayali provinces. The region includes the Boqueron del Padre Abad gorge through the Cordillera Azul.
These are sub-Andean rivers, typically fast-flowing where they cut through the Cordillera Azul foothills before spreading across lower gradients. Like other rubbernose plecos, C. sacramento is presumed to occupy riffle and rapid zones with rocky substrates, where current ensures high dissolved oxygen and continual renewal of the periphyton biofilms on which the species feeds. No formal water chemistry data from collection sites have been published for this species.
Feeding
Chaetostoma sacramento is an aufwuchs grazer. Its ventral disc mouth and fine rasping teeth are adapted for scraping periphyton — the mixed biofilm of algae, diatoms, bacteria, and associated organic material — from rock surfaces. In the sub-Andean rivers it inhabits, fast turbulent flow keeps rock surfaces clean and continually resupplied with nutrients, supporting dense periphyton communities.
In aquarium care, the diet should be strongly plant-based: quality spirulina wafers, algae discs, blanched courgette (zucchini), cucumber, and similar vegetables form the core. Rocks and smooth wood surfaces colonised by natural algae or biofilm are valuable dietary supplements and provide natural foraging stimulation. Animal protein should be offered sparingly and should never dominate the diet.
Mating
No specific courtship observations for C. sacramento in the wild or in captivity have been published. The general Chaetostoma pattern, inferred from related species, involves males establishing and defending territories around suitable spawning sites — rocky crevices, undercut ledges, or cave-like recesses in riffle zones. Males develop elongated interopercular odontodes during the reproductive season, which serve both in male-male competition and in courtship displays. Gravid females become noticeably broader-bodied than males of similar size.
Breeding
No captive breeding records for C. sacramento are documented in the published or hobbyist literature available at the time of writing. The species was only formally described in 2024, though it has circulated in the aquarium trade for longer under its provisional L-numbers.
Based on the cave-spawning biology common to Chaetostoma and loricariids more broadly, breeding is likely to involve deposition of adhesive eggs within a sheltered crevice or rocky cavity, followed by paternal guarding and fanning of the clutch. Conditioning attempts should prioritise clean, highly oxygenated water with strong circulation, a diet rich in vegetable matter, and — where possible — a gradual temperature reduction to simulate seasonal variation in the sub-Andean rivers of origin.
In the aquarium
As a rheophilic species from fast sub-Andean rivers, C. sacramento requires water quality and flow rates that reflect its natural environment. High dissolved oxygen, vigorous circulation, and scrupulously low nutrients are not optional; this fish will decline in still, warm, or poorly maintained water. Strong powerheads or circulation pumps, combined with efficient mechanical and biological filtration, are the foundation of appropriate care.
At under 3 in SL, this is a genuinely compact pleco that can be accommodated in a well-filtered aquarium of around 20–25 US gal, provided flow rates are high. Rock-work should be the primary décor — smooth and textured stones, slate, and flat-faced boulders provide grazing surface, shelter, and breeding sites. Driftwood can be included but is not the focus of the diet as it would be for wood-eating species such as Panaqolus or Panaque.
The variability in spot pattern that once led to three separate L-numbers means that specimens from different river systems within the Pampa de Sacramento region may look quite different — from finely spotted to more boldly vermiculated — while being the same species. This morphological variation is not a cause for concern and reflects the species' natural intraspecific diversity.
C. sacramento is believed to be peaceful toward unrelated species. Conspecific tolerance in small tanks may be limited, particularly between males. Tankmates should tolerate strong current and clean, well-oxygenated water.
Conservation
Chaetostoma sacramento has not been evaluated by the IUCN Red List and carries the status Not Evaluated. Described only in 2024, the species has not been the subject of any formal conservation assessment.
Its known range encompasses several rivers within the Pampa de Sacramento region of central Peru — a landscape that faces pressure from agricultural expansion, coca cultivation, and road-building associated with development of the Huánuco and Ucayali hinterlands. The Cordillera Azul National Park, which overlaps part of the region, provides some habitat protection, but the degree to which it covers the specific river systems occupied by this species is not documented in the available literature.
Given the recent formal description and the relatively narrow geographic range documented so far — three river systems within a single sub-Andean plain — a future IUCN assessment would be informative. The presence in the ornamental trade under multiple L-numbers indicates that at least some collection pressure has existed, though the extent and sustainability of that collection are unknown.