Taxonomy & naming
Leporinus microphthalmus was described by the Brazilian ichthyologist João Carlos Garavello in 1989. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) confirms it as a currently valid species within Leporinus, a large genus of South American headstanders placed in the family Anostomidae, order Characiformes. ITIS carries a corresponding taxonomic record (TSN 641283) for the name.
The genus Leporinus has historically been treated broadly, and molecular and morphological work over the past few decades has reshaped anostomid classification considerably, including the erection of segregate genera for some species once placed here; nothing in the available sources suggests L. microphthalmus itself has been affected by such a move, and it remains listed under Leporinus. The species epithet microphthalmus is Greek for "small-eyed," a descriptive name referring to the fish's eye size relative to its head, and distinguishing it from larger-eyed congeners in formal keys.
Morphology
Leporinus microphthalmus is a small member of its genus, reaching a maximum recorded standard length of 4.5 in — noticeably smaller than well-known aquarium headstanders such as the banded leporinus, which can exceed 10 in. As its name implies, its eyes are comparatively small relative to head size, a useful field character for separating it from similar-looking congeners in the same river system.
Like other Leporinus, it has an elongated, moderately compressed body, a small subterminal mouth adapted for grazing, and the genus-typical dentition suited to scraping algae, biofilm and plant material from hard surfaces. Detailed published descriptions of its colour pattern and fin morphology beyond the original species description were not found in the available sources; readers should treat any specific colour claims with caution until confirmed against the primary literature.
Habitat
The species is recorded from the Paraná River basin in Brazil, with its type locality given as the Rio Araguari at the Salto de Nova Ponte waterfall near Nova Ponte, in the state of Minas Gerais. This places it in the same broad drainage as many other headstanders and headwater characins of southeastern Brazil's subtropical plateau country, an area with a more pronounced cool season than the equatorial Amazon.
Specific water-chemistry data for this species was not found in the available sources. As a general guide for Paraná-basin characins, expect flowing, well-oxygenated water over rock and wood, with temperatures running cooler in winter than typical equatorial Amazon conditions; keepers should not assume the warm, soft blackwater parameters often generalised for Neotropical fish without confirming them for this particular drainage.
Feeding
Leporinus microphthalmus is a grazer in the pattern typical of its genus, feeding in the oblique, head-down posture that gives headstanders their common name. It picks algae and biofilm (aufwuchs) from submerged wood, rock and vegetation, supplementing this with small invertebrates and, opportunistically, soft plant material.
In the aquarium a Leporinus of this type should be offered a vegetable-forward diet — blanched vegetables, spirulina-based foods and algae wafers — alongside occasional protein such as bloodworm or quality pellets. Because grazing headstanders will readily turn to soft-leaved aquarium plants when other grazing surfaces run short, robust or unpalatable plant species are a safer choice for a planted setup housing this genus.
Mating
No courtship or pairing behaviour specific to Leporinus microphthalmus was found in the available sources. Research on the wider genus describes headstanders spawning over weedy or vegetated substrate, but detailed observations for this particular species — spawning triggers, pair formation, or any external sexual dimorphism — are not documented in the sources reviewed here. This account does not speculate beyond what is recorded.
Breeding
Leporinus microphthalmus is not known to be bred in the aquarium hobby. Headstanders in this genus are generally egg-scatterers over vegetation with no parental care, and a small number of Leporinus and related Anostomus species have been reported spawning in captivity or reared commercially on fish farms, but no breeding record specific to this species was found in the available sources.
Given the almost complete absence of published reproductive data for this species, any aquarium breeding attempt would be working from genus-level generalities rather than confirmed information for L. microphthalmus itself.
In the aquarium
Leporinus microphthalmus is essentially unknown in the aquarium trade, and this account should be read as a caution rather than a care guide. At a modest maximum size of 4.5 in SL it is smaller than most commonly kept Leporinus, which would in principle make it more manageable in a home aquarium than the larger banded species — but like its relatives it should still be expected to nip fins and graze on soft plants, since these are genus-wide traits rather than exceptions.
Any keeper who does encounter this species should provide flowing, well-oxygenated water with algae-covered wood and rock for grazing, robust rather than delicate plants, and tankmates too fast or too large to be viewed as fin-nipping targets. Given how little is documented about its behaviour and requirements in captivity, this is a species for the experienced, research-minded keeper rather than a routine community-tank choice.
Conservation
Leporinus microphthalmus has not been evaluated by the IUCN Red List; its conservation status is Not Evaluated. This is common for narrow-range or infrequently surveyed characins of Brazil's interior river systems, and Not Evaluated should not be read as evidence of either safety or risk.
No specific threats or population trend data for this species were found in the available sources. Its type locality at a named waterfall on the Rio Araguari places it in a Paraná-basin drainage subject to the general pressures facing southeastern Brazilian rivers — damming and hydropower development in particular — but no source reviewed here documents how, or whether, those pressures affect this species specifically.