Taxonomy & naming
Hypostomus crulsi was described by Soares, Aquino, Bagley, Langeani and Colli in 2021, in the same Journal of Fish Biology paper that simultaneously described H. cafuringa. The two species are both endemic to Distrito Federal, Brazil, but belong to different river basins: H. crulsi inhabits the upper Paraná basin, while H. cafuringa occurs in the upper Tocantins basin. The Catalog of Fishes (Eschmeyer, CAS) recognises Hypostomus crulsi Soares et al. 2021 as a valid species.
The type locality is ribeirão Taquara, a tributary of rio São Bartolomeu in the Paranaíba River drainage, upper Paraná River basin, Distrito Federal, Brazil (approximately 15°54'S, 47°54'W, elevation 1,115 ft).
H. crulsi is characterised by a combination of: dark spots on a pale background, absence of abdominal plates, a shorter first ray of both the pelvic and pectoral fins relative to congeners, and a small body size. These characters collectively distinguish it from H. cafuringa and from other regional species despite the superficially similar pigmentation pattern.
Morphology
Size data for H. crulsi are not reported in the available sources. The original description notes small body size as a diagnostic feature, suggesting adults are modest in length by Hypostomus standards, but a specific standard length or total length figure is not recorded in the accessible literature.
The body armour follows the loricariid ground plan: overlapping odontode-bearing scutes covering the head and flanks, with the abdomen notably lacking plates — a character shared with sister species H. cafuringa and used diagnostically. Coloration is described as dark spots on a pale background. The first rays of the pelvic and pectoral fins are proportionally shorter than in closely related species.
No fin-ray counts or other meristic data were available from the sources consulted.
Habitat
Hypostomus crulsi is known from the headwaters of rio São Bartolomeu, upper Paraná River basin, Distrito Federal, Brazil, with the type locality at ribeirão Taquara at an elevation of approximately 1,115 ft above sea level. This places it among the highest-elevation records for the genus in central Brazil.
The streams of Distrito Federal in this basin are Cerrado headwater systems — typically rocky or gravelly, with clear, relatively shallow water and moderate to strong flow. Seasonal variation in the Cerrado means these streams contract markedly in the dry season and expand during wet-season rains. No water-chemistry measurements are reported for the collection sites.
The species was described as occurring in habitat under conversion pressure from agriculture, indicating the landscape surrounding its streams has been substantially altered from native Cerrado vegetation.
Feeding
No feeding observations for H. crulsi exist in the wild or in captivity. Based on genus membership and its rocky headwater habitat, the species almost certainly feeds by scraping aufwuchs — epilithic algae, cyanobacteria, and associated fine organic detritus — from submerged rock surfaces using its sucker mouth and tooth battery, the standard feeding mode of Hypostomus.
Data sparse; inference from loricariid biology only.
Mating
No mating behaviour has been recorded for H. crulsi. Whether sexual dimorphism in fin length or odontode development is present, as in many Hypostomus species, is not reported in the available sources.
Data sparse.
Breeding
No breeding data exist for H. crulsi in the wild or captivity. The species has not been recorded in the aquarium trade and no spawning reports are known.
Data sparse.
In the aquarium
Hypostomus crulsi is not known from the ornamental fish trade and no husbandry information is available. It was described from remote headwater streams in Distrito Federal at over 1,0 ft elevation, well outside the range of routine collection for the aquarium trade.
Data sparse.
Conservation
Hypostomus crulsi has not been evaluated by the IUCN Red List as of the time of writing. The species was flagged in its original description as warranting conservation attention: it is endemic to a small number of headwater streams within a single sub-basin of the upper Paraná in Distrito Federal, Brazil, and its habitat is under active pressure from agricultural conversion of the Cerrado landscape.
The Cerrado is a globally recognised biodiversity hotspot and one of the most heavily converted biomes on Earth; its endemic freshwater fauna, which includes numerous suckermouth catfish with highly restricted ranges, face particular risk because stream headwaters are often the last refugia for species that cannot disperse past watershed divides. The high-elevation type locality at ribeirão Taquara (1,115 ft) places H. crulsi in a habitat type that is especially sensitive to changes in riparian vegetation — headwater streams lose shading, bank stability, and organic input rapidly when native gallery forest is removed.
Formally, the conservation status is Not Evaluated; ecologically, its narrow endemism and degraded landscape context suggest priority for targeted survey work.