Taxonomy & naming
Ancistrus aguaboensis was described by Fisch-Muller, Mazzoni and Weber in 2001 in Ichthyological Exploration of Freshwaters (volume 12, number 4, pages 289–304) under the title 'Genetic and morphological evidences for two new sibling species of Ancistrus (Siluriformes: Loricariidae) in upper rio Tocantins drainage, Brazil.' The holotype (MNRJ 20850) and paratypes were collected from the Córrego Água Boa, a minor left-bank tributary of the Rio Bonito, itself a tributary of the upper Tocantins, approximately 6 mi from Minaçú–Campinaçu, at 13°35'S, 48°14'W, Goiás State, Brazil.
The Catalog of Fishes (Eschmeyer, CAS, updated June 2026) treats Ancistrus aguaboensis Fisch-Muller, Mazzoni & Weber 2001 as the valid name with no subsequent synonyms. It sits in subfamily Hypostominae, tribe Ancistrini, within the large family Loricariidae (Armbruster, 2004). The genus Ancistrus Kner, 1854 is one of the most species-rich loricariid genera, comprising over 70 described species; it is distinguished by the conspicuous soft dermal tentacles (odontodes) on the snout of mature males — a character unique in the family. The species epithet derives from the type locality stream: Córrego Água Boa in Portuguese means 'good water creek,' and the suffix -ensis is Latin, denoting origin or provenance.
Morphology
Adults reach a maximum of 2.5 in standard length (SL), making A. aguaboensis among the smaller members of an already compact genus. The body is strongly depressed, notably wide relative to its depth, with the typical loricariid armour of overlapping bony scutes covering the flanks and dorsum. Ground colour is dark brownish-grey to nearly black, overlaid with numerous small whitish to pale yellowish spots distributed across the body and fins — the dorsal and other fins show this pale-spotted pattern on a brownish background, while the lips and belly are predominantly unpigmented, yellowish to cream.
Diagnostic characters from the original description include a short dorsal fin base (3.6–4.1 times in SL), a wide ventrally-positioned sucking mouth, and an exposed nuchal plate that is minute or entirely covered by skin. The supraoccipital plate is often slightly depressed. Dermal plates along the dorsal-fin base number 6–7, and the interdorsal distance is short (5.1–5.5 times in SL). Meristics: 1 dorsal spine + 7 dorsal soft rays; 1 anal spine + 4 anal soft rays; 28 vertebrae.
Sexual dimorphism is the same as for other Ancistrus: mature males develop the characteristic branched soft tentacles on the snout, and often shorter supplementary tentacles along the interopercular margin. Females may occasionally develop a few marginal tentacles but never the elaborate branched array of the male. Gravid females are noticeably broader when viewed from above. The papilla, though small, is also sexually differentiated.
Habitat
The type locality — Córrego Água Boa in the upper Tocantins drainage — lies within the Cerrado biome of central Brazil, characterised by seasonally variable rivers draining ancient shield and sedimentary substrates. FishBase and PlanetCatfish place the species within the upper Tocantins and Araguaia systems, suggesting a distribution across the headwater zone of this major basin.
The Tocantins rises in the central Brazilian plateau and flows northward some 2,373 mi to the Amazon estuary. Its upper sections in Goiás State consist of clear to slightly turbid streams with predominantly rocky and gravelly substrate; the original description specifies riffles with 'predominantly rocky substratum with some gravel and sand.' Such habitats are well-oxygenated, often with moderate to strong current, and experience marked seasonal fluctuation: a pronounced dry season (April–September) concentrates fish in pools and runs, while the wet season (October–March) expands habitat enormously.
A. aguaboensis occurs in the benthic riffle zone, pressing itself against rock surfaces using its ventral sucker and rasping periphyton biofilm. At 2.5 in SL it can exploit narrow crevices and rock undersides unavailable to larger loricariids sharing the same river.
Feeding
Like all Ancistrus, A. aguaboensis is primarily a periphyton and biofilm grazer. Using its wide, fleshy sucker mouth equipped with numerous bicuspid teeth, it rasps algae, diatoms, fungi, and associated organic matter from hard substrates — rock faces, submerged wood, and aquatic macrophytes. In riffle habitats, biofilm production is high because current constantly replenishes nutrients over illuminated rock surfaces, providing a renewable food source.
The species is not a dedicated xylophage in the manner of Panaqolus or Panaque; wood may be exploited opportunistically for the biofilm it carries rather than as a primary nutritional substrate. Gut content analyses of congeners suggest a diet dominated by algae and detritus with occasional microinvertebrates.
In the aquarium, the standard Ancistrus diet applies: high-quality sinking algae wafers and spirulina-based pellets as staples, supplemented with blanched vegetables (courgette/zucchini, cucumber, sweet potato). Small amounts of meaty foods such as bloodworm can be offered occasionally. Driftwood should be present as enrichment even if not nutritionally essential. Overfeeding protein should be avoided.
Mating
Courtship in A. aguaboensis follows the general Ancistrus pattern and has been observed in aquarium settings, though specific published accounts for this species are limited. Males establish and defend territory around caves, crevices, or other confined spaces that provide spawning sites. As in other bristlenoses, males bearing well-developed tentacles are dominant, and tentacle size and branching may function as honest signals of male quality during female assessment.
A conditioned female will approach the male's territory; the male courts by displaying and positioning himself near or inside the chosen cavity. Females are significantly broader-bodied than males when gravid, making sex identification straightforward once both sexes are mature. Males may cohabit with more than one female in a larger tank with multiple spawning sites, but two males in a small space risk sustained territorial conflict including fin damage from interopercular odontode sparring.
Breeding
Ancistrus aguaboensis is a cave-spawner with paternal brood care — the standard loricariid breeding mode shared across the genus. The male selects a tight cavity (a hollow piece of driftwood, a ceramic tube, a narrow rocky crevice) and after spawning the female departs, leaving the male as sole guardian.
PlanetCatfish records four aquarium breeding reports for this species, confirming its tractability in captivity. Eggs are adhesive, typically pale amber to yellowish, and are deposited in a compact cluster on the cave interior. The male fans the clutch continuously with his pectoral fins to maintain oxygenation and removes any fungused eggs. Incubation lasts roughly 5–7 days at 75–79 °F. Newly hatched larvae carry a prominent yolk sac and remain within the cave; the male continues to guard until the yolk is absorbed (a further 2–4 days) and the fry begin actively grazing. Fry accept finely powdered spirulina or algae wafer from the outset.
Conditioning adults with varied diet, clean water, and a slight temperature drop followed by warming can trigger spawning. Caves of suitable dimensions (just large enough for the male to turn around) increase breeding success.
In the aquarium
At a maximum of 2.5 in SL, A. aguaboensis is genuinely nano-compatible — a distinction worth emphasising when most fish sold simply as 'bristlenose' in pet stores may be the larger Ancistrus cirrhosus or A. temminckii, which can reach 4.5–6 in. A single adult can be kept in 15 US gal; a breeding pair or trio is comfortable in 20–25 US gal with adequate rock and wood structure.
Water parameters should reflect the warm Cerrado headwater origin: temperature 73–81 °F (PlanetCatfish data), soft to moderately hard water (the Tocantins headwaters are generally low in dissolved minerals), pH neutral to slightly acidic. The species is not especially fastidious within these ranges, but water quality must be high — ammonia and nitrite at zero, low nitrate, regular partial water changes of 25–30% weekly.
Hardscape is essential: smooth flat rocks, rough volcanic rock, and a piece or two of driftwood replicate the riffle substrate and provide grazing surfaces and hiding places. Breeding caves (hollow sections of wood, ceramic tubes) should be provided if breeding is intended. Plants are compatible and safe, as A. aguaboensis focuses on biofilm rather than leaf tissue.
The species is peaceful toward heterospecifics. Males may spar briefly over territory but serious injury is uncommon where adequate hiding space is available. Compatible with small tetras, rasboras, Corydoras, small livebearers, and most community species of similar scale.
Conservation
The IUCN Red List assessed Ancistrus aguaboensis as Least Concern in 2018, reflecting a distribution within the upper Tocantins drainage and no evidence of significant population decline. The species appears tolerant of a degree of habitat variation and the upper Tocantins, though impacted by agriculture and sedimentation, still supports riffle habitats across a reasonable area.
However, the broader Tocantins basin has experienced substantial hydrological modification, most notably the construction of the Tucuruí Dam (commissioned 1984) — the world's fourth-largest hydroelectric reservoir — which transformed the lower and middle Tocantins. The upper basin where A. aguaboensis occurs lies above the main impoundment zone, but ongoing agricultural expansion, cattle ranching, and deforestation in the Cerrado continue to increase sediment loads and alter flow regimes in headwater streams. Loss of riffle habitats through siltation is a real medium-term threat.
Captive breeding in the hobby is documented, and tank-raised specimens reduce pressure on wild collections. The species' compact size and adaptability make it feasible to breed in modest aquaria, supporting a potential supply of captive-bred animals.