Taxonomy & naming
Chaetostoma anale was originally described as Hypocolpterus analis by Henry Weed Fowler in 1943 in the Proceedings of the Academy of Natural Sciences of Philadelphia (volume 95, pages 261, figures 56–59). The type locality is Río Orteguasa, Florencia, Caquetá Department, Colombia, and the unique holotype is deposited at the Academy of Natural Sciences of Philadelphia (ANSP 70525). The species was subsequently treated as Hypocolpterus analis by Isbrücker (1980) and Burgess (1989), transferred to Chaetostoma as Chaetostoma analis by Burgess & Finley (1996) and Isbrücker (2001), and finally emended to the neuter form Chaetostoma anale by Isbrücker (2002), following the ICZN Code gender agreement rules since Chaetostoma (Tschudi, 1846) is neuter. The Catalog of Fishes (Eschmeyer, CAS; updated 10 June 2026) recognises the valid name as Chaetostoma anale (Fowler, 1943). The parenthetical authority reflects the original description in a different genus (Hypocolpterus).
Molecular tissue samples of C. anale collected from the Orteguasa and Caquetá rivers in Colombia (GenBank OL303592–OL303605) were included in the species-delimitation analyses of Meza-Vargas et al. (2022) and the 2024 revision of the new Ucayali Chaetostoma species, confirming the taxon's phylogenetic placement within the Andean cis-Andean Chaetostoma clade. No L-number has been assigned to this species. The name Chaetostoma vagum is treated as a synonym of this species in Eschmeyer's Catalog of Fishes.
Morphology
Chaetostoma anale reaches a maximum standard length of 6.5 in SL (Fisch-Muller in Reis et al. 2003), making it one of the larger species in a genus where most members stay below 6 in SL. Body form is the characteristic compressed-depressed shape of Chaetostoma: broad, flat head with a wide fleshy snout lacking bony plates on its anterior and anterolateral margins (shared with all Chaetostoma except the outlier C. platyrhynchus). This naked-snout condition — a broad band of unplated skin framing the disc — is what gives Chaetostoma the 'rubbernose' common name and immediately distinguishes it from Ancistrus, which instead bears fleshy tentacles rather than a flat naked snout margin.
Coloration based on available images and the original description indicates a dark grey to brownish base with variable patterning; the Caquetá-Orteguasa specimens are reported to lack distinct white spots on the head (in contrast to some sympatric or nearby congeners that have strongly spotted heads). Molecular and morphological analysis by Lujan et al. (2015) and Meza-Vargas et al. (2022) place C. anale in the broader Andean cis-Andean clade alongside species such as C. changae, C. taczanowskii, and C. marginatum.
Sexual dimorphism follows the Chaetostoma pattern: males develop a larger, broader head and more slender ventral profile than females, and notably, males have disproportionately large pelvic fins thought to function in directing sperm onto egg clutches in fast-flowing water — inverting the pelvic fins over the clutch may prevent sperm dispersal by the current.
Habitat
Chaetostoma anale is known from the Orteguasa River, an upper Caquetá tributary draining the Andean foothills near Florencia, and from the main Caquetá drainage in southern Colombia. The Caquetá River (known as Japurá in Brazil) originates in the Colombian Andes, descends through rapidly flowing piedmont streams and foothill reaches, then broadens into a large lowland Amazonian tributary.
Both the Orteguasa and the broader upper Caquetá drainage where this species occurs are Andean-influence rivers characterised by high gradient, coarse rocky substrate, high dissolved oxygen from turbulent flow, warm temperatures in the piedmont zone (approximately 73–79 °F), and low to moderate conductivity. The substrate in productive rubbernose habitat consists of large boulders, bedrock outcrops, and cobble fields with heavy periphyton and algal mat growth on upstream-facing rock faces — precisely the microhabitat to which Chaetostoma's powerful ventral suction disc and robust body form are adapted.
The Caquetá system is influenced by Andean geology and experiences a bimodal rainfall pattern typical of the Colombian foothills, with wet seasons broadly from March to June and October to December driving increased discharge and turbidity. In drier periods, lower water levels concentrate fish in deeper channel pools between rocky rapids.
Feeding
Chaetostoma anale is a periphyton and aufwuchs specialist, feeding primarily by rasping algal films, diatom mats, and associated microorganisms from the surfaces of rocks and boulders in fast-flowing water. The broad, unplated snout acts as a firm adhesion pad against the substrate while the strong jaws and teeth scrape material from the rock face. The genus is particularly well adapted to feeding in the high-oxygen turbulent zones of Andean foothill rapids, where current creates mechanical stress that most fish species cannot tolerate but where the food supply — dense algal crusts on sun-exposed boulders — is exceptionally productive.
In the aquarium, C. anale and other Chaetostoma require a similar herbivore-biased diet supplemented with vegetables and algae. Algae wafers, spirulina-based sinking foods, and blanched courgette (zucchini), cucumber, sweet potato, and leafy greens are all accepted. Chaetostoma can sometimes be reluctant to feed in the early acclimation period after import and may benefit from live foods (bloodworm, small crustaceans) and fresh vegetables to stimulate feeding. Once established, individuals are typically robust feeders.
Mating
Courtship and mating behaviour in C. anale has not been documented in detail in the primary literature, and the species has no registered breeding reports on PlanetCatfish. The mating system is inferred from the general Chaetostoma pattern described for congeners.
Male Chaetostoma are territorial around suitable spawning sites — typically the underside of a flat slab or overhanging ledge in fast-flowing shallow water. The disproportionately large pelvic fins of males are thought to serve a function during fertilisation in fast-water environments: by arching or inverting the pelvic fins over the egg clutch immediately after the female deposits eggs, the male may create a localised low-velocity zone that allows sperm to remain in contact with the eggs rather than being swept away by the current. This is a proposed functional interpretation and has not been formally tested in published field experiments for this species.
Breeding
Chaetostoma anale is reported to spawn in shallow, fast-flowing water on the underside of a flat object — typically a rock slab or boulder surface — with the male guarding the adhesive egg clutch by covering it with his body (PlanetCatfish Cat-eLog). This 'guarding-by-covering' behaviour is typical of fast-water rheophilic plecos that spawn in exposed locations rather than enclosed caves, as it provides physical protection and maintains a boundary layer of water over the eggs.
No confirmed aquarium spawning reports exist for this species. For hobbyists wishing to attempt breeding, the key requirements are: high water flow and dissolved oxygen (a powerhead or spray-bar creating vigorous surface agitation), flat smooth rock slabs positioned to create shallow sheltered overhangs, cool and oxygen-rich well-maintained water (73–77 °F), and good conditioning of both sexes on a varied herbivorous diet with some live or frozen invertebrate supplementation. Chaetostoma in general are considered challenging aquarium breeders, in part because their requirement for high oxygen levels and cool temperatures is at odds with the warmer conditions favoured by most tropicals in community settings.
In the aquarium
Chaetostoma anale is occasionally exported from Colombia as part of the ornamental fish trade — PlanetCatfish records photographs of the species from the Río Caquetá — though it is far less commonly available than the more widely kept Chaetostoma species from the Orinoco drainage. At up to 6.5 in SL, it is among the larger members of the genus and requires a tank of at least 25–40 US gal for a single adult or a pair.
The most important aquarium requirement for this species — and for Chaetostoma generally — is high dissolved oxygen. Slow, warm, low-oxygen water is physiologically stressful and likely to cause rapid decline in newly imported wild-caught individuals. Strong surface agitation from a canister filter spray-bar or powerhead, an undersized water volume relative to the pump output, and regular water changes are all essential. Water temperature of 73–78 °F (PlanetCatfish data) and pH 6.7–7.6 reflect the Andean foothill origin; water need not be extremely soft, but heavily mineralised hard water from a chalk or limestone catchment is inappropriate.
Decor should replicate the rocky habitat: large smooth river stones, slate, and flat slabs arranged to create crevices, ledges, and overhangs. Substrate can be fine gravel or sand. Strong directional flow from a powerhead placed to create current-breaks is beneficial. Plants are secondary to rockwork in terms of priority; Java fern, Anubias, and Bolbitis attached to rocks are all suitable additions that tolerate the high flow. Chaetostoma are generally non-aggressive toward non-Chaetostoma species, though males may posture and skirmish with one another in confined spaces.
Conservation
Chaetostoma anale was assessed as Data Deficient by the IUCN Red List in October 2014, reflecting insufficient information at the time of assessment to determine whether population declines or threats met threshold criteria for a threatened category. The Data Deficient designation is not equivalent to 'not threatened'; it simply indicates that the available information was insufficient to make a determination.
The species is known only from the upper Caquetá-Orteguasa system in the Colombian Andean foothills — a region that has been subject to significant land-use change, including coca cultivation and eradication (fumigation), cattle ranching and forest clearance on Andean slopes, and oil exploration in the adjacent Putumayo basin. Andean foothill streams feeding rivers like the Orteguasa are vulnerable to increased sedimentation when riparian vegetation is removed, which can smother the rocky periphyton substrates these rheophilic catfishes depend upon.
Molecular sequencing samples from the Orteguasa and Caquetá collected in the context of 2022–2024 revisionary work confirm the species is extant and collectible in those systems, but population-level monitoring data are lacking. A future reassessment with improved geographic range data may result in an upgrade to a threatened category if surveys document range contraction. Until such data exist, the Data Deficient assessment stands.