Taxonomy & naming
Hypostomus arecuta was formally described by Cardoso, Almirón, Casciotta, Aichino, Lizarralde and Montoya-Burgos in 2012 in Zootaxa (volume 3453, pages 56–68). The holotype (MACN-ict 10150) was collected at the type locality of Ituzaingó, Corrientes Province, Argentina, in the Paraná River at approximately 27°29'54.5"S, 56°42'47.0"W — the middle Paraná channel, a large, fast-flowing river draining much of subtropical South America.
The species epithet is taken directly from Guaraní: *arecuta* is the word used by Indigenous communities of the region for loricariid catfishes in general. The choice reflects both the fish's deep presence in the regional landscape and the authors' recognition of traditional ecological knowledge.
Within the genus Hypostomus — by far the largest genus in Loricariidae with well over 150 valid species — H. arecuta is diagnosed by a distinctive combination of characters: light, roundish dots on a darker background (a colour pattern shared by few sympatric congeners) and a particular count of premaxillary and dentary teeth. It was described alongside seven or more other Hypostomus species known from the same river reach, underlining the extraordinary regional diversity of the group. The Catalog of Fishes (Eschmeyer, CAS) lists Hypostomus arecuta as the valid combination.
Morphology
Hypostomus arecuta reaches a maximum recorded standard length of 9.5 in (SL), placing it in the mid-size range for the genus. The body follows the characteristic loricariid plan: a flattened ventral surface suited to life on the substrate, a domed dorsum, and a complete covering of keeled bony scutes arranged in lateral series. The caudal peduncle is relatively slender; the dorsal fin is large and sail-like when erect.
The colour pattern is the most distinctive external feature: pale, roundish dots scattered on a darker brown to dark olive background, with the dots being notably light and relatively circular rather than elongated or forming streaks. This pattern is consistent enough to aid identification in the field among the dense Hypostomus assemblage of the middle Paraná. Belly coloration is paler, as typical in the genus.
The oral disc is ventrally positioned and broad, equipped with numerous bicuspid teeth on both the premaxilla and dentary — the specific tooth counts provide diagnostic characters separating H. arecuta from congeners in formal identification. Like all Hypostomus, the species is capable of facultative air-breathing, ingesting atmospheric oxygen via the stomach when dissolved oxygen levels fall, an adaptation useful in warmer, slow-moving side channels.
Habitat
Hypostomus arecuta inhabits the coastal main channel of the middle Paraná River in Corrientes Province, Argentina. This is a large, powerful river system carrying substantial volumes of mixed-origin water — Andean snowmelt, subtropical highland rain, and lowland drainage — yielding broadly neutral water chemistry with a pH reported near 6.8–7.1 and moderate oxygen content in the main flow.
Microhabitat preference centres on boulder-dominated substrates in zones of moderate current. The fish adhere closely to hard rocky surfaces, using the broad oral disc as a suction anchor while rasping algal and periphytic biofilm. Large boulders and cobble fields in the main channel provide both feeding substrate and refuge from the river's considerable hydraulic force. The species co-occurs with at least eight other Hypostomus in this system — one of the most species-rich pleco assemblages in the Americas — presumably partitioned partly by substrate preference, depth, and micro-current zone.
The middle Paraná is a large lowland river with a pronounced seasonal flood pulse; water levels, current speed, and turbidity all vary markedly between wet and dry seasons, and H. arecuta inhabits a system shaped by this rhythm.
Feeding
Like the majority of Hypostomus, H. arecuta is a benthic grazer whose primary food is the periphyton — the complex assemblage of algae, cyanobacteria, diatoms, and associated organic material (aufwuchs) that colonises submerged hard surfaces. The bicuspid teeth and broad oral disc are well-suited to scraping this material from boulder faces and bedrock outcrops in moderate current.
In addition to algal biofilm, loricariids in the Paraná system ingest fine detritus, sand, and organic particulates that adhere to rock surfaces or settle in crevices; the digestive tract of Hypostomus is accordingly long, allowing protracted microbial fermentation of plant cell walls. Invertebrate prey items may be consumed opportunistically when encountered on the substrate, but the diet is predominantly plant-derived material.
No specific feeding observations for H. arecuta in captivity are documented in the available literature. Husbandry can be extrapolated from the wider genus: algae wafers, spirulina-based foods, blanched vegetables (courgette, cucumber, spinach), and sinking pellets form a suitable captive diet, supplemented by natural aufwuchs growth on rocks and driftwood within the aquarium.
Mating
No specific observations of mating behaviour in Hypostomus arecuta have been published. Reproductive biology can be inferred from the well-studied pattern common across Hypostomus: males typically defend cavities or crevices in rocky substrate — natural equivalents of the root hollows and undercut banks used by other species — and display to females during the breeding season.
Sexual dimorphism in Hypostomus is generally subtle outside the breeding season. In reproductively active males, elongated odontodes on the interopercle (cheek region) and along the body scutes become more pronounced, serving as both rival signals and tactile stimuli during courtship. Females ready to spawn show a noticeably rounder, wider body profile when gravid.
As with other mid-Paraná Hypostomus, breeding is likely tied to the seasonal flood cycle and associated temperature and rainfall cues. No captive breeding records for H. arecuta are known.
Breeding
No confirmed breeding records for Hypostomus arecuta in captivity or detailed in-situ accounts exist in the available literature. The species was described only in 2012 and has not entered the ornamental trade in any documented quantity.
By analogy with well-studied Hypostomus relatives, the species is presumed to be a cavity or crevice spawner. Males guard the eggs and fan them with the fins to maintain oxygenation; paternal care continues through early larval development until fry can fend for themselves. Clutch sizes in the genus vary widely by species size; mid-sized species (8–12 in SL) typically produce clutches of several hundred eggs.
Given the species' association with boulder substrate in moderate current, spawning sites in nature likely include undercut rock faces, deep crevices between boulders, or submerged root masses along the river bank — all of which provide shelter from current and predators. Any future captive attempts would likely benefit from replicating these conditions: robust water flow, rocky caves or dense tube structures, and seasonal temperature variation to simulate the Paraná flood cycle.
In the aquarium
Hypostomus arecuta is not established in the ornamental fish trade and is unlikely to be encountered outside specialist collections or imports from Argentina. The species has no L-number and has generated very limited hobby attention since its 2012 description.
Its size — approaching 9.5 in SL, with total length correspondingly larger — places it in the category of plecos requiring genuinely large aquaria; a tank of at least 80–105 US gal with strong filtration and vigorous water movement would be the minimum for a single adult, reflecting the high-energy, well-oxygenated main-channel habitat it occupies in the Paraná. Substrate should include large, smooth river stones or cobble, and open swimming space should be provided alongside hiding crevices.
Water chemistry should reflect the Paraná origin: broadly neutral pH (6.8–7.5), moderate temperature (no specific field data are recorded, but the subtropical Paraná in Corrientes Province experiences roughly 64–82 °F seasonally), and good oxygenation. Turbid water can be tolerated given the naturally silty main-channel environment.
Diet follows standard mid-sized Hypostomus husbandry: periphyton from hard surfaces, supplemented with algae wafers, blanched vegetables, and sinking pellets. Any aquarist obtaining this species should be prepared for a long-lived, large, waste-producing animal — as with any large loricariid — and for the virtual absence of published husbandry experience to draw on.
Conservation
Hypostomus arecuta has not been evaluated by the IUCN Red List and carries no formal conservation status. The species is known from the middle Paraná River in Corrientes Province, Argentina, where it co-occurs with a high diversity of other Hypostomus; occurrence records confirmed from GBIF fall within this province.
The Paraná River is one of South America's major rivers and faces multiple pressures: dam construction (the Yacyretá reservoir immediately upstream of the known range has altered flow dynamics and sediment loads), channelisation, agricultural runoff, and ongoing water withdrawal. Changes to flow regime, sediment dynamics, and boulder-substrate stability can all affect benthic loricariids that depend on hard-substrate biofilm as their primary food source.
The broader Hypostominae assemblage of the Paraná is well-studied by Argentine ichthyologists, and H. arecuta was confirmed as a valid species through that body of work. No specific data on population size or trend are available. A formal IUCN assessment would be needed to quantify any conservation concern.