Taxonomy & naming
Leporinus microphysus was described by James Birindelli and Heraldo Britski in 2013, part of a wave of species-level revisions that untangled the long-confused Leporinus of the rio Tapajós basin. The type locality lies within that basin in the Brazilian state of Pará, and the description places the species alongside several superficially similar Tapajós endemics — L. britskii, L. parvulus and L. vanzoi — distinguishing it chiefly by a reduced swim bladder and a lateral-line scale count of 38 to 40, together with its pattern of a dark midlateral stripe and dark transversal bars across the dorsum.
The genus Leporinus sits in the family Anostomidae — the headstanders — within Characiformes, and the Catalog of Fishes (Eschmeyer, California Academy of Sciences) currently recognises roughly 80 valid species spread across the Amazon, Orinoco, Paraná-Paraguay and Guianas drainages, several of them, like this one, still known only from their original description. No published common or trade name for L. microphysus was found in the available literature; it is referred to here by its scientific name.
Morphology
As with other members of its genus, Leporinus microphysus has the characteristic headstander build: an elongated, moderately compressed body, a small terminal-to-subterminal mouth suited to scraping rather than gulping, and a colour pattern of a dark stripe running along the flank overlaid with dark bars crossing the back. The original description separates it from its closest Tapajós relatives on the basis of a reduced gas bladder and a lateral line carrying 38–40 scales, both fine anatomical characters rather than obvious field marks.
Exact maximum size has not been reported in the sources available for this account. Most small-to-medium Leporinus species top out well under the largest members of the genus, which can approach 15.5–19.5 in, but until a specific figure for L. microphysus is published, keepers should assume a moderate adult size typical of Tapajós Leporinus rather than the genus's largest extremes, and plan the tank generously rather than optimistically.
Habitat
Leporinus microphysus is known from the rio Tapajós basin, a major clearwater tributary of the Amazon in Brazil, an environment of rocky and sandy river channels, submerged wood and rapids-influenced stretches that support a dense grazing community of algae- and biofilm-feeding fish. Detailed water-chemistry data specific to the collection sites were not available in the sources reviewed here.
More broadly, Tapajós clearwater habitats tend to run warm and only mildly acidic to circumneutral, distinct from the deeply tannin-stained blackwater rivers elsewhere in Amazonia — but without species-specific measurements this should be treated as regional context rather than a confirmed profile for L. microphysus, and precise pH and hardness figures for the species are data-sparse.
Feeding
Leporinus as a genus are grazers and aufwuchs feeders, working algae and biofilm off submerged wood, rock and vegetation in the head-down, oblique posture that gives headstanders their common name, while also taking small invertebrates and readily browsing soft aquatic plants. Nothing in the available sources suggests L. microphysus departs from this pattern, and its small, scraping mouth is consistent with the same grazing lifestyle documented across its relatives.
In the aquarium, this translates to a diet built around vegetable matter — blanched vegetables, algae wafers and spirulina-based foods — supplemented with some protein such as small live or frozen invertebrate foods. Keepers should not expect a predatory or purely carnivorous fish, and should expect it to sample any soft-leaved plants in the tank.
Mating
No courtship behaviour specific to Leporinus microphysus has been documented in the sources available for this account. Across the genus generally, spawning is tied to seasonal cues — rising water levels and the chemistry shifts of the flood season — rather than to any elaborate pair-bonding display, and external sexual dimorphism is not well documented for most Leporinus, including this species.
Breeding
Leporinus microphysus has not been reported bred in the aquarium, and the genus as a whole is only rarely spawned in captivity. Where Leporinus breeding has been documented at all — mostly in a handful of larger, more widely traded congeners — it follows the pattern typical of migratory Neotropical characins: an egg-scattering spawn over open substrate or fine vegetation in seasonally flooded habitat, triggered by rising water and falling conductivity, with no parental care of eggs or fry afterward.
Given the complete absence of species-specific breeding accounts for L. microphysus, keepers should not expect to reproduce it under normal aquarium conditions, and any claim of home breeding for this particular species should be treated with caution until documented.
In the aquarium
Leporinus microphysus is essentially unknown in the aquarium trade — this account is built from the original taxonomic description and from genus-level knowledge of Leporinus, not from hobbyist experience with this specific fish. Prospective keepers should treat it accordingly: size it for a substantial, long, well-filtered tank appropriate to a mid-sized-to-large grazing characin, furnish it with driftwood and rock for grazing surfaces plus open swimming room, and expect a robust appetite for algae, vegetables and soft plants.
The genus's best-documented behavioural trait is territoriality that sharpens with age and close quarters: many Leporinus and their anostomid relatives are notorious fin-nippers as adults, and tankmates should be chosen for robustness and speed rather than delicate fins. Until more is known about L. microphysus specifically, keepers should assume it shares this temperament rather than assume it is the exception.
Conservation
Leporinus microphysus has not been evaluated by the IUCN Red List and carries a status of Not Evaluated. It is a recently described, range-restricted Tapajós basin endemic, and like many such recently split Leporinus it has not yet attracted a dedicated conservation assessment, so there is no documented population trend or specific threat data to report.
The rio Tapajós basin more broadly faces well-documented pressures from hydroelectric damming, mining-related sedimentation and deforestation, all of which are long-term watch items for its endemic fish fauna even though none has been formally linked to this species in the available literature.