Taxonomy & naming
Chaetostoma pearsei was described by Carl H. Eigenmann in 1920 in Indiana University Studies (volume 7, number 44, page 8, Figure 3, Plate 2). The type locality is the Río Castaño at Maracay, Aragua state, Venezuela — a stream that flows into Lake Valencia (Lago de Valencia). The species was originally placed in Chaetostomus, a spelling variant that appears in some older references; the valid current combination is Chaetostoma pearsei Eigenmann, 1920 as recognised by the Catalog of Fishes (Eschmeyer, CAS).
The L-number designation L187 was assigned by DATZ for this species, providing a hobbyist-recognition code that predates its widespread identification under the scientific name in the trade. In Venezuela the fish is known under the local common name Corroncho — a term broadly applied to sucker-mouth catfishes in the northern coastal region — and in Denmark it circulates as Finneplettet Gumminæse (spot-finned rubber nose).
Within Chaetostoma, the species belongs to the Hypostominae subfamily and tribe Ancistrini, sharing the defining characters of the rubber-nose pleco group: interopercular odontodes, absence of abdominal plates, and the highly mobile, fleshy snout that gives the clade its popular name.
Morphology
Chaetostoma pearsei reaches approximately 6 in standard length (SL) — mid-sized for the genus and roughly consistent with the FishBase-reported maximum of 6 in TL (though TL normally exceeds SL, the published figures from different sources may reflect measurement inconsistency; PlanetCatfish gives 6 in SL as the size reference). The body carries the full loricariid plate armour, with the broad, depressed head and flexible, fleshy snout characteristic of Chaetostoma.
Dimorphism in this species follows the Chaetostoma genus pattern documented in the PlanetCatfish records. Males have a proportionally larger and broader head, a slimmer ventral profile, and conspicuously disproportionate pelvic fins. These enlarged pelvic fins are functionally interpreted as reproductive structures: during spawning in fast current, the male is thought to fold the pelvic fins over the freshly deposited egg clutch, creating a localised shelter that allows sperm to contact eggs before being swept away by the current — a rare and specialised adaptation to rheophilic breeding. Interopercular odontodes (cheek bristles) are more developed in breeding males. Females in spawning condition show a swollen, rounded papilla and greater girth when viewed from above.
Habitat
The natural range of Chaetostoma pearsei is divided between two basins in north-central Venezuela: the Tuy River drainage, which flows east to the Caribbean coast, and the Lake Valencia (Lago de Valencia) basin, an endorheic (internally draining) basin at approximately 1476 ft elevation in the Cordillera de la Costa. The type locality at Río Castaño near Maracay is within the Lake Valencia catchment.
The co-occurrence of C. pearsei in both basins — despite the Tuy draining separately to the Caribbean and the Lake Valencia basin being closed — suggests either historic hydrological connections within the Cordillera de la Costa or dispersal through shared headwater zones. The region around Maracay and the Aragua valley sits at a topographic junction where multiple small drainages originate in close proximity.
Within these basins, C. pearsei occupies clear, fast-flowing, highly oxygenated streams and small rivers over rocky substrates. PlanetCatfish data give field parameters of pH 6.8–7.5 and temperature 75–78 °F — soft to moderately mineralised, well-oxygenated Andean-foothill-type water. The species is a rheophile and a facultative air-breather.
Feeding
Chaetostoma pearsei is a grazer on epilithic algae and periphyton — the biofilm of algae, bacteria, and fine organic matter that accumulates on rock surfaces in fast, clear streams. The flexible, fleshy snout allows tight conformity to irregular rock surfaces, and the ventral sucker-mouth rasps material without releasing grip on the substrate even in swift current. This is the core foraging ecology of the genus.
In the aquarium, an established coating of algae on rocks and glass is a valuable food resource. Supplementary feeding with algae wafers, spirulina-based sinking pellets, blanched courgette (zucchini), cucumber, and similar vegetable foods is appropriate. Presenting food in areas of current encourages natural foraging posture and activity. Protein supplementation should be modest — Chaetostoma are not carnivores.
Mating
Mating in Chaetostoma pearsei has not been described in published papers, but the strongly dimorphic pelvic fins in males indicate a functional reproductive role consistent with that hypothesised for the genus. During spawning in fast-flowing water, the male's oversized pelvic fins are thought to invert over the egg clutch, forming a partial shield against current that keeps sperm in contact with eggs long enough for fertilisation — an unusual reproductive strategy adapted to the rheophilic lifestyle.
Males are expected to be territorial around preferred spawning sites: flat-faced rocks or cobble undersurfaces in areas of brisk current. A well-furnished tank with stacked rounded stones creating multiple crevices mimics the natural microhabitat and supports natural territorial behaviour without serious aggression.
Breeding
Like other Chaetostoma, C. pearsei is a fast-water substrate spawner. Spawning takes place on the underside of flat rocks or cobbles in shallow, high-velocity water. The female deposits adhesive eggs on the ceiling of this substrate cavity, and the male subsequently brood-guards by positioning himself inverted — ventral side up — with his body covering and protecting the clutch. This ventral brooding posture in fast current is a behavioural adaptation seen across the genus.
PlanetCatfish lists two registered keepers and three wild spotters for C. pearsei but no documented captive breeding events. Clutch size is not published for this species. Hobbyists attempting to breed Chaetostoma species generally recommend: strong, directed current, flat rocks arranged as potential spawning sites, cool-to-moderate temperatures, and thorough conditioning of both sexes on a diet rich in algae and vegetables before attempting to trigger spawning.
In the aquarium
Chaetostoma pearsei (L187) is occasionally available through specialist catfish dealers and is one of the more recognisable Venezuelan rubber-nose plecos in the European trade, though it is not common. Its modest adult size — around 6 in SL — makes it suitable for medium-sized aquaria of 25 US gal or more, provided the most critical requirement is met: strong, directional water movement.
The single non-negotiable in husbandry is current. Without a powerhead or spray bar generating meaningful flow, C. pearsei will be stressed, may surface-breathe excessively, and will lose condition. High dissolved oxygen and cool, clear water (75–78 °F, pH 6.8–7.5) should be maintained. The substrate should consist primarily of well-rounded stones, stacked to create sheltered crevices and flat-roofed caves — the furniture that satisfies territorial and breeding instincts simultaneously.
The diet is vegetable-forward: algae on glass and decor is valuable, supplemented by algae wafers, spirulina pellets, and blanched vegetables. Courgette (zucchini) and cucumber weighted to the bottom near a current outlet are typically accepted readily. Peaceful in community settings with fish that share its current preference; avoid housing with sluggish or very large tankmates.
Conservation
Chaetostoma pearsei has not been evaluated by the IUCN Red List and carries no formal conservation status. The species is restricted to north-central Venezuela — the Lake Valencia basin and the Tuy drainage — a region under considerable and ongoing human pressure.
Lake Valencia (Lago de Valencia) is an endorheic lake that has experienced severe environmental degradation over the twentieth century, including eutrophication from agricultural and urban runoff, water-level fluctuation driven by abstraction and diversion, and widespread riparian deforestation around its catchment streams. The streams entering the lake from the Cordillera de la Costa — including the type-locality drainage near Maracay — have contracted significantly in quality and flow. The Tuy River basin similarly drains a heavily urbanised and agricultural corridor south of Caracas.
Although no population data exist for C. pearsei, the combination of restricted range and severe catchment degradation in both basins suggests that a formal IUCN evaluation might find the species at some level of concern. The absence of a captive-breeding programme or a significant aquarium trade population means no safety net exists outside the wild.