Taxonomy & naming
Chaetostoma nudirostre was formally described by Lütken in 1874 in the Videnskabelige Meddelelser fra den Naturhistoriske Forening i Kjøbenhavn (Aaret 1873, nos 13–14, p. 207). The type locality is Valencia, Venezuela — that is, the Lake Valencia basin. An early synonym, Chaetostomus nudirostris, circulated in older literature and reflects the gender-inflected variant spelling; the Catalog of Fishes (Eschmeyer, CAS) recognises Chaetostoma nudirostre as the valid name.
The species was later referenced in diagnostic characterisations by Fernandez-Yepes (1945, p. 29) and by Ceas and Page (1996, p. 674), and was redescribed by Steindachner (1881, p. 120, pl. 5, figs. 2, 2a). In the aquarium trade it is most widely known under its DATZ L-number, L188, and by the vernacular Light Rubbernose — a name that reflects the pale snout tip and soft-snouted profile characteristic of the species.
Chaetostoma belongs to the tribe Ancistrini within the subfamily Hypostominae (Loricariidae). The genus is distinguished from the superficially similar Ancistrus by the absence of fleshy branched tentacles on the snout; Chaetostoma males instead bear enlarged interopercular odontodes (spines projecting from behind the gill cover), and the snout itself is naked — lacking the plate armour that covers the snout in many loricariid genera. The main reference for the family-level placement is Fisch-Muller (2003), Loricariidae-Ancistrinae, in the Checklist of the Freshwater Fishes of South and Central America.
Morphology
FishBase records a maximum total length of 5 in TL for this species; PlanetCatfish reports a size of 5 in SL from the type material, suggesting the two figures are broadly consistent when caudal fin length is accounted for. The body form is typical of the genus: depressed and flattened ventrally, with the mouth enlarged into a broad, muscular sucker disc well adapted for adhesion to smooth rock surfaces in swift current.
The most diagnostic external character is the naked snout — the rostral area lacks the plates present in many related genera, giving the species its name (Latin nudi = bare, rostrum = snout). Interopercular odontodes are present, projecting laterally from behind the gill cover; these are especially pronounced in adult males. The abdomen is unplated, another feature shared across Chaetostoma. Coloration is typically brown to olive with a variable pattern of pale spotting or reticulation; the belly is paler. Genus members are facultative air-breathers, able to supplement gill respiration by gulping atmospheric air, an adaptation likely linked to hypoxic or shallow-water microhabitats.
Sexual dimorphism follows the Chaetostoma pattern: males have a proportionally broader, more robust head, slimmer ventral sides, and disproportionately large pelvic fins. The enlarged pelvic fins are functionally significant — in fast-current spawning scenarios, they appear to aid the male in covering the egg clutch while braced against the substrate.
Habitat
Chaetostoma nudirostre is known from the Lake Valencia basin in Carabobo state, northern Venezuela. Lake Valencia (Lago de Valencia) is an endorheic lake — it has no surface outlet — fed by Andean-foothills streams draining from the surrounding cordillera. The inflowing rivers and streams where rubbernose plecos of this genus are typically found tend to be fast-flowing, clear, and well-oxygenated, with rocky or boulder-strewn substrates.
As in other Chaetostoma species, the microhabitat preference is for exposed rock surfaces in areas of meaningful current, where the ventral sucker disc allows the fish to remain stationary against the flow while grazing the biofilm. The genus is broadly associated with montane and submontane fast-water environments across northwestern South America. Specific water parameter records from the Lake Valencia drainage are sparse in the available cache data, but surrounding Venezuelan fast-water rivers generally range from soft to moderately hard, with temperatures reflecting altitude — typically 68–79 °F in tributary streams. Dissolved oxygen is consistently high in these lotic habitats.
Feeding
Chaetostoma nudirostre is a periphyton and biofilm grazer — an aufwuchs specialist in the loricariid mould. In nature it rasps thin films of algae, diatoms, cyanobacteria, and fine organic detritus from rock surfaces using its broad, transversely arranged teeth. The species is not a wood-eater; driftwood is not a dietary requirement, though it may rasp algae from submerged surfaces of any material.
In the aquarium, the diet should centre on algae-based foods: high-quality algae wafers, spirulina discs, and sheets of blanched nori (dried seaweed). Natural algae growth on rocks and glass panels supplements the diet and encourages natural grazing behaviour. Blanched vegetables — courgette (zucchini), cucumber, and sweet potato — are accepted. Supplementary protein from small invertebrates can be offered occasionally but should not dominate the diet; this is a predominantly herbivorous species. Consistent feeding and a tank with some natural algae growth are important for long-term condition.
Mating
Courtship behaviour in Chaetostoma follows the general pattern documented for the genus in both wild observations and aquarium breeding reports. Males are territorial around sheltered spawning sites — typically the underside of a flat rock or a cave-like recess formed by stacked boulders. During the breeding period, the male's interopercular odontodes become more prominent, and he will defend his chosen site against rival males with lateral displays and, if necessary, physical contact.
Females entering the male's territory are assessed; a receptive female is courted and guided toward the prepared spawning surface. The disproportionately large pelvic fins of the male, noted under Morphology, are understood to play a role in covering and protecting the egg mass during and after fertilisation — a functional adaptation to spawning in exposed, fast-current sites where the eggs are not hidden within a cave but are deposited on a surface exposed to water flow.
Breeding
Chaetostoma nudirostre spawns on the underside of flat objects in fast-flowing water, a strategy consistent across the genus. The adhesive egg clutch is deposited upside-down on the underside of a flat rock or similar object, and the male remains with the clutch, guarding it against disturbance and maintaining water circulation around the eggs by fanning with his fins.
In the aquarium, breeding is best encouraged by replicating the natural habitat: well-rounded, stacked stones forming caves and overhangs, strong current from a powerhead or spray-bar, and high dissolved oxygen. Flat slate or smooth stones placed in the current zone can serve as spawning surfaces. Conditioning on a varied algae-rich diet and performing regular partial water changes to maintain water quality and simulate seasonal variation are generally beneficial. The male's attentive paternal guarding continues until the fry are free-swimming.
In the aquarium
At a maximum total length around 4.5–5 in, Chaetostoma nudirostre is a medium-sized rubbernose pleco — larger than the commonly kept Chaetostoma thomsoni but manageable in a reasonably sized tank. A tank of 25 US gal or more is appropriate for a single specimen or a small group, with the critical furnishing being a rocky substrate with stacked boulders that create caves, overhangs, and turbulent flow paths. Current is important: a strong filter return or powerhead directed across the rock layout keeps oxygen high and the fish active and healthy.
Water chemistry should reflect the species' Venezuelan highland origin: temperature 68–79 °F, pH 6.5–7.5, soft to moderately hard water. The species is sensitive to poor water quality and low oxygen; regular partial water changes and efficient filtration are non-negotiable. Algae growth on rocks and glass is welcome and provides a continuous grazing surface.
Chaetostoma nudirostre is generally peaceful toward other species. Like all Chaetostoma, it can be territorial toward conspecifics and other plecos competing for the same rock territory; multiple hiding spots reduce conflict. It is well-suited to community tanks with schooling fish that occupy open water — characids, small barbs, and rasboras are compatible. Avoid keeping with fish that will compete directly for the rocky bottom territory, and avoid overly warm conditions that reduce dissolved oxygen below the species' comfort range.
Conservation
Chaetostoma nudirostre has not been evaluated by the IUCN Red List and carries a status of Not Evaluated (NE). The species is endemic to the Lake Valencia basin of northern Venezuela — an endorheic drainage that has experienced significant anthropogenic pressure over the twentieth and twenty-first centuries. Lake Valencia and its tributary streams have been subject to water extraction for agriculture and urban supply, pollution from industrial and domestic effluent around the densely populated Carabobo–Valencia corridor, and introduced species.
Although no formal population assessment exists, the restricted basin range and the environmental pressures on the Valencia drainage are reasons for concern. Fast-water tributary habitats — the microhabitat type this species depends on — are disproportionately affected by agricultural sedimentation and flow alteration. Formal evaluation of its conservation status would be a useful step toward understanding whether the species warrants protection. In the aquarium trade, it is present in modest numbers under the L188 code, but captive breeding programmes are not widely established.