Taxonomy & naming
Hassar wilderi was described in 1895 and placed in the genus Hassar, one of several genera of thorny catfishes in the family Doradidae. Doradids have been reshuffled repeatedly as ichthyologists have revised the group, and older literature sometimes shifts species between Hassar and neighbouring doradid genera; the Catalog of Fishes treats Hassar wilderi as the currently valid combination, and that is the name used here.
The species epithet honours Burt Green Wilder (1841–1925), an American comparative anatomist and neurologist best known for his work on brain anatomy at Cornell University. The genus name Hassar is of uncertain, likely local South American origin, applied to this group of Amazonian and Tocantins thornback catfishes. The Portuguese common name recorded for the species, "botinho", reflects its use and recognition by fishers within its native Brazilian range.
Morphology
Hassar wilderi reaches a real maximum size of about 10 in total length, a solidly built, bottom-dwelling catfish rather than a small, tank-friendly species — keepers should plan around the adult size, not the size of the juvenile usually sold. Like other doradids it carries rows of bony lateral plates (scutes) along the flanks in place of true scales, giving the body a thorny, armoured feel rather than smooth skin.
The head and body carry three pairs of barbels used to feel out food on and in the substrate, and the fins are armed with stiff, serrated spines at the leading edge of the dorsal and pectoral fins. These spines lock erect and can be rasped to make sound (the "talking catfish" habit shared across Doradidae), and they readily snag in aquarium nets — a fish this size is best moved in a submerged container rather than netted, both to protect the fish's spines and to avoid a jab to the keeper's hand.
Habitat
The species is endemic to the Tocantins River basin in Brazil, a major Amazon-adjacent drainage in South America. It is a demersal fish, living on or near the riverbed rather than in open water, and favours soft, fine sand substrates that it can sift through with its barbels while foraging.
Water in its native range runs warm, in the region of 72–77 °F, with reports from the aquarium literature suggesting a neutral to slightly acidic, soft-water chemistry around pH 6.5–7.0. This fits the general pattern of soft, warm Amazonian tributary water rather than anything harder or more mineral-rich, though detailed field data on hardness for this specific species is sparse.
Feeding
Hassar wilderi is a nocturnal, benthic omnivore, foraging mostly after dark along the bottom for small invertebrates, detritus and other opportunistic food items, consistent with its mid-level position (trophic level around 2.8) in the food web of its home river.
In the aquarium it takes sinking tablet and pellet foods readily, along with small live and frozen fare such as bloodworm and Daphnia. Because it is most active at night, offering food after the lights go out helps ensure it gets its share rather than being out-competed by more visible, day-active tankmates.
Mating
Detailed field or aquarium observations of courtship and spawning behaviour in Hassar wilderi are not available in the sources consulted here — data sparse. What can be said with confidence is that, as a scaleless-skinned, plated doradid rather than a bubble-nesting callichthyid or an internally fertilising auchenipterid, it does not fit either of those better-known catfish breeding templates; nothing in the available sources supports assigning it a specific mating strategy.
Breeding
Hassar wilderi is not reported as an aquarium-bred species in the sources available for this profile — data sparse, and no credible breeding mode should be assumed. Many doradid catfishes outside the bubble-nesting callichthyids are simply not reproduced in home aquaria, with any commercial supply coming from wild collection rather than captive spawning.
Prospective keepers should treat this as an essentially unbred aquarium fish for now: enjoy it as a long-lived community member rather than a breeding project, and note any successful spawning as noteworthy rather than expected.
In the aquarium
This is a large-growing catfish for its group — a real adult length of about 10 in — so it needs a spacious, mature aquarium with a soft, fine-sand substrate that lets it sift and forage naturally without abrading its sensitive barbels. A well-planted tank with root tangles or driftwood to retreat into by day suits its largely nocturnal habits better than open rockwork.
Temperament is reported as notably non-aggressive for a catfish of this size, and it can be housed with small characins, dwarf cichlids, small labyrinth fish and other small catfish without trouble; keeping a group of three or more is recommended over a lone individual, as it is a social species in the wild. Two care points matter most: its scaleless, plated skin makes it medication-sensitive, so copper-based treatments and anthelminthics should be dosed conservatively (half-dose is often advised); and it is reported as more prone to infection than its relative H. orestis, meaning consistently clean, pristine water is essential rather than optional. As with other doradids, handle it in a container rather than a net to avoid tangling its locking spines.
Conservation
The IUCN Red List assesses Hassar wilderi as Least Concern. As a species endemic to the Tocantins basin, its long-term status is nonetheless tied to the health of that specific river system, which has faced substantial hydrological change from dam construction and development elsewhere in the basin; the current Least Concern rating does not remove the value of watching basin-wide pressures over time.
No specific population trend or habitat threat detail was available in the sources used for this profile. Aquarium specimens in the trade are understood to derive from wild collection within its native Brazilian range rather than captive breeding.