Taxonomy & naming
Spatuloricaria tuira was described by Fichberg, Oyakawa, and de Pinna in 2014 in Copeia (volume 2014, number 2, pages 317–324, figures 2–4). It was described directly into Spatuloricaria — there are no synonyms. The type locality is the Rio Jamanxim near Vila Mil, Novo Progresso, Pará State, Brazil (7°43'51"S, 55°16'36"W), in the Tapajós drainage. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Spatuloricaria tuira Fichberg, Oyakawa & de Pinna, 2014.
The species was the first new Spatuloricaria described in nearly 70 years, ending a long gap in the genus's described diversity. Within the genus, S. tuira is distinguished from all congeners except S. nudiventris by having the abdominal surface completely naked (unplated) rather than covered in abdominal scutes, and by the absence of preanal plates. From S. nudiventris it is distinguished by having five transversal dark-brown dorsal bands (versus four in S. nudiventris and S. fimbriata) and by a unique pattern of dark-brown irregular stripes on the head.
The genus Spatuloricaria belongs to the subfamily Loricariinae within Loricariidae, characterised by the greatly elongate, depressed body and filamentous caudal extension typical of the whiptail catfishes.
Morphology
Spatuloricaria tuira reaches approximately 18 in total length (TL) at maximum size, making it a large whiptail catfish. The body is elongate and depressed, with a broad flattened head and the characteristic long caudal filament of the genus. The abdominal surface is completely unplated — naked — a key diagnostic character distinguishing S. tuira from most other Spatuloricaria. Preanal plates are absent. Coloration features five transversal dark-brown bands across the dorsal surface and a distinctive pattern of irregular dark-brown stripes on the head, not seen in other congeners.
Spatuloricaria tuira is unique within its genus for exhibiting reversed sexual size dimorphism: mature males range 3.5–6 in SL, while females grow substantially larger. This is the only Spatuloricaria in which mature males are measurably smaller than mature females — a biologically unusual situation among loricariids. Males develop odontodal growth on the cheeks and thicker pectoral fin spines in breeding condition, and the male head is isosceles-triangle shaped versus the more equilateral female head, consistent with the pattern across Spatuloricaria.
Habitat
Spatuloricaria tuira is known from the Rio Xingu and Rio Tapajós drainages of Pará State, Brazil. Both are major southern tributaries of the Amazon, draining the Brazilian Shield and carrying clear to moderately turbid water with sandy, rocky, and gravel substrates in their faster-flowing sectors. FishBase references note that S. tuira occurs on the bottom of medium to large rivers, associated with rocky or sandy substrates in fast-flowing sectors — a habitat consistent with its classification as a demersal benthopelagic species in tropical freshwater.
PlanetCatfish recommends water current that is brisk to strong for this species in aquaria, consistent with the fast-water microhabitats recorded in the field. Suitable parameters based on hobbyist and FishBase data: temperature 79–84 °F, pH 6.0–7.4. A habitat shot in the PlanetCatfish image gallery shows the fish against substrate bearing algae and Aufwuchs biofilm, the primary food base. The Xingu drainage is subject to significant pressure from the Belo Monte hydroelectric complex; the species' presence also in the Tapajós means its entire range is not confined to the most impacted zone.
Feeding
Spatuloricaria tuira is a benthic grazer, feeding on Aufwuchs biofilm — the complex community of algae, diatoms, cyanobacteria, and associated microorganisms that colonises submerged rock and sandy surfaces in well-lit, flowing river sectors. The presence of algae and biofilm in habitat images confirms the dietary base. In the aquarium, fast water current and moderate to bright lighting promote Aufwuchs growth on rock surfaces, partially meeting the fish's grazing needs. Supplementary feeding should focus on sinking algae wafers, spirulina tablets, and blanched vegetables. Fresh zucchini and cucumber on a clip placed near the current outlet are readily accepted by most grazing loricariids and are appropriate here.
Mating
No captive breeding of Spatuloricaria tuira has been reported. The reversed sexual size dimorphism — males maturing at 3.5–6 in SL, substantially smaller than females — is a biologically unusual condition and may have implications for the dynamics of mate selection and territorial behaviour. In many loricariids, the male is the larger and more territorial sex; the reversal in S. tuira suggests either that female body size confers a reproductive advantage (perhaps in egg production capacity), or that male size is constrained by early maturation.
Males in breeding condition are identifiable by odontodal development on the cheeks and thicker pectoral spines, and by the head-shape difference noted for the genus. Conditioning for breeding should include a varied diet, brisk water movement, and water parameters in the suitable range. A large, well-oxygenated aquarium with sandy and rocky substrates would be the appropriate environment for a breeding attempt.
Breeding
No breeding report for Spatuloricaria tuira has been published or recorded in the PlanetCatfish database. Based on the biology of Loricariinae, paternal open-substrate brooding — the male guarding an egg mass on sandy or rocky river bottom — is the expected reproductive strategy. The naked abdomen of S. tuira may be relevant to the brooding posture; in some loricariinae the male uses the broad, unplated ventral surface to cradle or press the egg mass against the substrate.
The reversed size dimorphism means that a breeding male would be notably smaller than the female he mates with — a pairing dynamic that keepers should keep in mind when selecting and conditioning a pair. Standard loricariinae breeding cues — a seasonal temperature drop followed by warming, high water quality, and a varied conditioning diet — are the most reasonable starting points in the absence of a species-specific breeding account.
In the aquarium
Spatuloricaria tuira is infrequently encountered in the hobby: four registered keepers and two spotters are listed on PlanetCatfish, with six images including a habitat shot. It is available through specialist importers, particularly from Brazilian-origin wild-caught shipments. The common names 'Tuira's Whiptail' and 'Marbled Xingu Whiptail' are used within the enthusiast community.
At up to 18 in TL, S. tuira is a large fish demanding correspondingly large aquaria. A minimum footprint of 150 × 23.5 in is advisable for a single adult; a breeding pair would require more. Brisk to strong water flow is a habitat requirement, and the filter outlet or a dedicated powerhead should provide significant current across the substrate. A mix of smooth sand and larger smooth pebbles or flat stones replicates the Xingu and Tapajós riverbed. Temperature should be kept in the 79–84 °F range, pH 6.0–7.4.
Algae growth on rock surfaces under moderate to strong lighting supplies part of the diet; supplementary sinking foods should be offered after lights-out when the fish is most active. Tankmates should be peaceful, fast-water-adapted species that will not compete on the substrate. The unique reversed size dimorphism means that a breeding male will be conspicuously smaller than the female in a pair — both fish should be well-conditioned before any spawning attempt is expected.
Conservation
The IUCN Red List assessed Spatuloricaria tuira as Least Concern in 2018 (IUCN ID 141063803). The assessment notes that the species occurs across both the Rio Xingu and Rio Tapajós drainages — a range broad enough that, despite significant hydroelectric pressure on the Xingu from the Belo Monte dam complex, the species is not considered threatened at a range-wide level.
The species' epithet itself reflects the conservation context: tuira honours a Mebêngôkre (Kaiapó) Indigenous woman who became a symbol of resistance against Xingu dam construction in approximately 1989, positioning this catfish within the long history of conflict over the Xingu's ecology and the communities that depend on it. The Belo Monte dam has altered hydrology, sediment dynamics, and substrate conditions in portions of the Xingu where fast-water and rocky-substrate species depend on specific habitat conditions. The Tapajós portion of the range faces emerging hydroelectric proposals. Monitoring of population response to these developments in both drainages would be valuable for future assessments.