Taxonomy & naming
Corumbataia tocantinensis was described by Heraldo A. Britski in 1997 in the publication 'Corumbataia tocantinensis: a new genus and species of the subfamily Hypoptopomatinae (Pisces, Siluriformes, Loricariidae)' (Comunicações do Museu de Ciências da PUCRS, Série Zoologia 10: 51–60). The holotype was collected from the Rio Vermelho, a tributary of the Rio Araguaia in central Brazil. In the same paper, Britski erected the genus Corumbataia and simultaneously described C. cuestae as a second congener, designating C. tocantinensis as the type species.
The Catalog of Fishes (Eschmeyer, CAS) recognises the valid name as Corumbataia tocantinensis Britski, 1997. The genus belongs to the subfamily Hypoptopomatinae within Loricariidae.
The original description attributed the species to both the Rio Araguaia and Rio Tocantins basins. Subsequent phylogenetic and morphological work — including a revision of the Corumbataia cuestae species group published in Neotropical Ichthyology — reassigned the Tocantins basin material to a newly described species, Corumbataia acanthodela, erected in 2020. The confirmed distribution of C. tocantinensis is therefore now restricted to the Rio Araguaia basin.
Morphology
Corumbataia tocantinensis is a diminutive loricariid. The type series examined in the revision spanned 0.5–1.5 in SL, and the species reaches a maximum of approximately 1.5 in SL — placing it among the smallest members of Hypoptopomatinae and among the smallest loricariids in any subfamily.
Morphologically, the species is characterised by an elliptical head profile in dorsal view, distinguishing it from relatives with a more rounded or pointed snout outline. A notable diagnostic character is the anastomosis (rejoining) of sensory canal branches over the pterotic-supracleithrum — a feature of the lateral-line canal system visible with close examination and used in phylogenetic analyses of the genus.
The body is covered with the typical overlapping bony scutes of Hypoptopomatinae. The ventral mouth is small and adapted to scraping aufwuchs from hard substrates. As in other members of the subfamily, the eyes are positioned laterally, providing a wide field of view.
Sexual dimorphism is not described in the available literature for this species.
Habitat
Corumbataia tocantinensis is now understood to be endemic to the Rio Araguaia basin of central Brazil. The type locality is the Rio Vermelho (a right-bank tributary of the Rio Araguaia), and all confirmed material of C. tocantinensis traces to Araguaia basin drainages. The populations originally attributed to the Rio Tocantins basin — a separate river system flowing roughly parallel to the Araguaia before the two join near Marabá — were formally reassigned to C. acanthodela in 2020.
The Rio Araguaia is a large, clear-water river system of the Brazilian Cerrado (tropical savanna) bioregion, characterised by sandy substrates, low turbidity, and moderate to low mineral content. Associated streams and tributaries such as the Rio Vermelho share these clear-water characteristics, with water that is generally soft and slightly acidic to neutral. The fish is benthopelagic, inhabiting the bed and lower water column of these streams.
No published temperature or water-chemistry measurements from C. tocantinensis collection sites appear in the available literature, but the Cerrado clear-water stream environment typically shows temperatures in the 72–82 °F range, soft water with low conductivity, and pH values around 6.0–7.5 depending on season and location.
Feeding
Corumbataia tocantinensis is presumed to be an algae and periphyton grazer, consistent with its Hypoptopomatinae affiliations and the small, scraping mouth characteristic of the genus. In the clear-water streams of the Araguaia basin, the fish likely scrapes aufwuchs — diatoms, cyanobacteria, green algae, and associated organic detritus — from sand grains, submerged wood, and rock surfaces.
No detailed stomach-content analyses for C. tocantinensis appear in the available literature. By analogy with close relatives of similar size and ecology, fine organic detritus and microalgae likely constitute the bulk of the diet. In captivity, if obtained, the species would be expected to accept algae wafers, spirulina, and blanched vegetables, consistent with care given to other small Hypoptopomatinae.
Mating
No accounts of courtship or mating behaviour in Corumbataia tocantinensis exist in the published scientific or hobbyist literature. The species is rare in the ornamental trade and has not been the subject of dedicated behavioural study.
Given the small body size and the general biology of Hypoptopomatinae, elaborate territorial defence or cave-site competition is unlikely. Mating behaviour in the genus is entirely undescribed.
Breeding
No captive breeding reports for Corumbataia tocantinensis are recorded in the available scientific or hobbyist literature. The species is rarely — if ever — available in the ornamental trade, and its reproductive biology in the wild remains unstudied.
The reproductive mode of the genus Corumbataia is unknown. No egg morphology, clutch data, incubation period, or parental care observations have been published. Any future attempt to breed the species in captivity would require close attention to replicating the clear, soft, mildly acidic water of the Araguaia basin tributaries, along with seasonal temperature and flow cues.
In the aquarium
Corumbataia tocantinensis is not established in the ornamental fish trade. It was described from scientific collections and has not been documented as a commercial import. Aquarists are unlikely to encounter it under this name; misidentifications with Otocinclus or other small Hypoptopomatinae from the same region are conceivable but unconfirmed.
Should the species become available, its small size (under 1.5 in SL) would make it suitable for nano or species aquaria. The clear-water Araguaia stream environment suggests soft, clean, well-oxygenated water with moderate flow, minimal waste load, and a substrate of fine sand. Dense plantings or biofilm-covered wood and stone surfaces would replicate the foraging habitat.
Given the range correction — the species is now understood to be an Araguaia basin endemic rather than a wider Tocantins/Araguaia species — any wild-collected material should be sourced and documented with care to avoid confusion with C. acanthodela from the Tocantins.
Conservation
The IUCN Red List assessed Corumbataia tocantinensis as Least Concern, with the assessment completed on 7 November 2018. The assessment was based on the species' distribution across the Araguaia and Tocantins basins as understood at that time; the subsequent restriction of C. tocantinensis to the Araguaia basin alone (following the description of C. acanthodela in 2020) narrows the effective range on which the Least Concern determination was based.
The Rio Araguaia basin faces conservation pressures from agricultural expansion, particularly soy cultivation and cattle ranching in the Cerrado region, which drive sedimentation and reduce water clarity in clear-water tributaries. The species' small body size and likely dependence on clear-water substrates could make it sensitive to increased turbidity. A reassessment incorporating the revised range would be informative but has not yet been published.