Taxonomy & naming
Sartor tucuruiensis was described by Santos & Jégu in 1987, placed in the small genus Sartor within the family Anostomidae — the headstanders — in the order Characiformes. The genus takes its name from the Tocantins region where it was collected, and the species epithet tucuruiensis refers directly to Tucurui, the town and, later, the site of the large Tucurui Dam on the lower Tocantins River in Pará state, Brazil.
Anostomidae has a long history of taxonomic revision, and the family's genera are distinguished largely by jaw structure, dentition and the angle at which the fish orients itself while feeding — the trait that gives the whole group its "headstander" common name. Sartor is a comparatively small and poorly studied genus within that family, and Sartor tucuruiensis in particular is known from a restricted stretch of the Tocantins basin rather than from a wide range, which has kept published information on the species sparse. The genus and combination follow the Catalog of Fishes (Eschmeyer, California Academy of Sciences), the standing authority for valid names.
Morphology
Sartor tucuruiensis is a small anostomid, with FishBase recording a maximum standard length of 4.5 in — modest even by headstander standards, and well short of the size many Leporinus and Anostomus species reach. As in other members of the family, the body is elongated and only moderately compressed, with a pointed head and a mouth positioned to feed obliquely rather than straight ahead.
The species carries tusk-like teeth in the lower jaw, an adaptation used to pick and pry insect larvae and other small food items from the underside of submerged wood — a more specialised feeding structure than the broader, rasping dentition of grazing anostomids. Detailed published description of colour pattern and fin morphology is limited in the sources available for this account; keepers and researchers should treat any specific colouration claims with caution absent a direct citation.
Habitat
The species is restricted to the Tocantins River basin in Brazil, with its type locality and known range centred on the Tucurui area of the lower Tocantins in Pará state. It is a tropical freshwater fish occupying a benthopelagic niche — associating with the bottom and the water column immediately above it rather than open midwater — consistent with its habit of feeding tipped down against submerged wood and other structure.
The lower Tocantins near Tucurui has been substantially altered by the Tucurui Dam, one of the largest hydroelectric projects in Brazil, which has fragmented river flow and flooded a large area of former river channel. Precise water chemistry data (temperature, pH, hardness) for the species' native habitat is not available in the sources reviewed for this account; given its Amazonian-basin origin it likely experiences warm, tropical conditions typical of Tocantins tributaries, but specific figures are not asserted here without a source.
Feeding
Sartor tucuruiensis is a specialist aufwuchs and insect-larva picker rather than a broad grazer. It feeds in the characteristic oblique, head-down posture of anostomids, using the tusk-like lower-jaw teeth to extract insect larvae and other small invertebrates from the surface of submerged wood, along with general aufwuchs (the biofilm of algae, microorganisms and detritus that coats underwater surfaces).
In an aquarium context this translates to a need for a varied diet built around small invertebrate foods and vegetable matter rather than flake alone — sinking foods that let the fish work a surface in its natural head-down posture are likely to suit it best, though specific husbandry feeding protocols for this species are not documented in the sources available.
Mating
Little is documented specifically about courtship behaviour in Sartor tucuruiensis. FishBase notes that the species breeds in densely vegetated places, which implies that ripe adults seek out heavy plant or root cover as a prelude to spawning, similar to reproductive behaviour reported in other small anostomids. No sexual dimorphism, courtship display or pairing behaviour is described in the sources reviewed for this account, and none is asserted here without a citation.
Breeding
As in other headstanders, Sartor tucuruiensis is understood to be an egg-scatterer rather than a nest-builder or mouthbrooder, releasing eggs among dense vegetation per the available FishBase account. There is no record in the sources reviewed of the species being bred in aquaria; unlike some larger, more commonly traded Leporinus and Anostomus species that are occasionally farmed or spawned by hobbyists, S. tucuruiensis appears to be essentially unknown in captive breeding, likely reflecting both its restricted range and its limited presence in the aquarium trade.
No parental care is documented for this species or reported broadly for egg-scattering anostomids, and none should be assumed.
In the aquarium
Sartor tucuruiensis is rarely, if ever, encountered in the aquarium trade, and specific husbandry data for the species is not available in the sources reviewed for this account. What can be said with some confidence, drawing on its documented biology, is that its modest adult size (around 4.5 in) makes it a far more manageable prospect than many larger anostomids, several of which are notorious fin-nippers that outgrow typical home tanks. FishBase and aquarium-trade notes describe the species as quarrelsome toward its own kind, though without inflicting serious injury — behaviour that suggests keepers should provide adequate space and visual cover if housing more than one individual together.
Given its specialised feeding style, a tank offering driftwood and other submerged structure for it to work in its natural head-down posture, plus dense planting reflecting its native breeding habitat, is a reasonable starting point. Because almost nothing about long-term care, water parameters or compatibility has been published for this species, any prospective keeper should treat it as an advanced, poorly documented fish rather than a straightforward community choice.
Conservation
Sartor tucuruiensis is assessed by the IUCN Red List as Endangered (EN), with the assessment dated 7 November 2018. The listing reflects the species' narrow, restricted range within the Tocantins basin combined with ongoing habitat degradation — criteria B2ab(iii), tied to a small area of occupancy and continuing decline in habitat quality.
The Tucurui Dam, completed on the lower Tocantins in the 1980s, fundamentally altered the hydrology of the area from which this species is known, and further development pressure in the Tocantins basin remains a relevant long-term threat to a fish with such a restricted distribution. As a narrow-range endemic with no significant role in the aquarium trade or fisheries, its conservation outlook depends almost entirely on the condition of its home river.