Taxonomy & naming
Hassar shewellkeimi was described by Mark H. Sabaj Pérez and José L. O. Birindelli in 2013 as a new species of thorny catfish (Siluriformes: Doradidae) from the upper Tapajós basin of Brazil. The holotype, MZUSP 110900, measures 7.5 in SL (7.5 in), collected from the rio Juruena above the mouth of the rio Arinos. The Catalog of Fishes recognises Hassar shewellkeimi as a valid species within the genus Hassar, a member of the thorny catfish family Doradidae, one of the diverse Neotropical catfish lineages that have been extensively revised — and had many new species split out of older, broadly defined genera — as taxonomists have worked through Amazonian material basin by basin.
As a comparatively recent description, Hassar shewellkeimi has not accumulated the tangle of historical synonyms seen in older Doradidae; it has always been placed in Hassar since its formal naming. The species epithet honours a collector or supporter associated with the fieldwork that produced the type material, a common convention in recent doradid descriptions from the Sabaj Pérez research program covering Tapajós-basin catfishes.
Morphology
Like other members of Hassar and the wider family Doradidae, this species carries rows of bony lateral plates (scutes) along the flanks rather than true fish scales — the armoured build that gives thorny catfishes their common name. The body is elongate and moderately compressed, with the stiff, serrated, locking spines typical of doradids at the leading edge of the dorsal and pectoral fins; these spines lock erect and can be rasped to produce sound, and they readily snag in a net.
FishBase lists a maximum size of 8.5 in SL for Hassar shewellkeimi, making it one of the larger species in its genus. This is a substantial fish for a Hassar and well above what casual keepers might expect from a "thorny catfish" — an adult needs a correspondingly large aquarium, and undersizing its housing is the most common care mistake made with fish in this family.
Habitat
Hassar shewellkeimi is known from the rio Teles Pires and the upper rio Juruena in Mato Grosso, Brazil, both tributaries of the Tapajós basin within the greater Amazon drainage. The type locality is the rio Juruena above the mouth of the rio Arinos. Genus-level field studies of Hassar describe these catfish as nocturnal and benthic, typically collected over sand in swift-flowing water — a habitat that demands good oxygenation and current rather than still, silted margins.
Water in the upper Tapajós system is warm, soft to neutral river water typical of the Amazon basin, with temperatures generally in the region of 79–82 °F. This is a running-water Amazonian species, not a blackwater specialist, and its restriction to a specific pair of tributaries within one sub-basin underlines how narrow its known range is.
Feeding
Genus-level research on Hassar describes these thorny catfish as nocturnal benthic foragers, working the riverbed after dark for invertebrates and detritus rather than actively hunting by sight. This fits the broader pattern seen across Doradidae, in which most species are opportunistic bottom feeders that sift and pick through sand and sediment for small prey.
Specific feeding data for Hassar shewellkeimi itself is sparse beyond this genus-level picture. Any aquarium account should follow the general doradid pattern — sinking foods offered after lights-out, since a strictly nocturnal bottom feeder is easily out-competed by diurnal tankmates at normal daytime feeding times.
Mating
No specific description of courtship or spawning behaviour for Hassar shewellkeimi has been documented in the available literature. As a Doradidae species from a remote stretch of the upper Tapajós, it has not been the subject of aquarium breeding reports or targeted reproductive studies.
Breeding
Breeding of Hassar shewellkeimi is not documented in the aquarium hobby or in the scientific literature reviewed here, and the species should be considered essentially unbred in captivity. Data on its reproductive mode — egg placement, parental care, or spawning triggers — is sparse to the point of being unknown; nothing here should be taken to imply open-water egg-scattering or any other specific mode without direct evidence. Given how recently the species was described and how narrow its known range is, it is best treated as a wild-collected fish for the foreseeable future, with no established home-breeding protocol.
In the aquarium
Hassar shewellkeimi is essentially unknown in the aquarium trade — there is no established husbandry record to draw on, and it should not be assumed to be readily available. Anyone who does encounter it should plan around its real adult size of 8.5 in SL: this is a good-sized catfish that needs a large, long aquarium with a sandy substrate and good water movement to reflect its swift-river, sand-bed habitat, not a small community tank.
As an armoured doradid, it carries bony lateral plates rather than bare skin, but like other spine-bearing catfish it should still be handled with care: the stiff, serrated, locking dorsal and pectoral spines can jab the keeper and tangle badly in a net, so it is safer to move in a container than to net directly. It is a nocturnal fish and will want caves, wood, or other cover to retreat into by day, emerging to forage after dark. With no husbandry track record, water parameters should conservatively follow its native Tapajós conditions — warm, soft-to-neutral river water rather than anything mineral-rich or alkaline.
Conservation
The IUCN Red List assesses Hassar shewellkeimi as Vulnerable (VU), as of a 2020 assessment. This status reflects its narrow known distribution, restricted to the rio Teles Pires and upper rio Juruena in the Tapajós basin of Mato Grosso — a region under mounting pressure from agricultural expansion, deforestation, and hydroelectric dam development across the Tapajós system.
Because the species is known from only a small part of one Amazon sub-basin, localized threats such as damming, sedimentation, or water-quality changes in the Teles Pires or Juruena rivers carry outsized weight for its overall conservation status. There is no indication that Hassar shewellkeimi is currently part of the aquarium trade, so collection pressure is not a documented concern; habitat change within its native rivers is the relevant risk.