Taxonomy & naming
Lepthoplosternum ucamara was described by Reis & Kaefer in 2005, part of a broader revision that split the old, unwieldy genus Hoplosternum into several smaller, more clearly defined genera — Lepthoplosternum, Megalechis, Callichthys and Hoplosternum in the strict sense. It belongs to the family Callichthyidae, the armored catfishes, in the subfamily Callichthyinae, the non-cory armored catfishes that includes the larger hoplo and Megalechis species alongside these small Lepthoplosternum. The Catalog of Fishes treats Lepthoplosternum ucamara as the valid name; older literature discussing similar dwarf hoplos from the region may still use the broader, now-superseded Hoplosternum.
The species epithet ucamara references Project Ucamara, an NSF-funded research initiative, and the Ucamara Depression, a geological subsidence feature of the upper Amazon foreland basin that shapes the low-lying floodplain reaches of the Ucayali and Marañón rivers where the species was collected. The holotype (MUSM 23000), a 2 in SL female, was taken from a small creek draining into Ucayali River floodplain vegetation — almost exactly the size the species reaches as an adult.
Morphology
Lepthoplosternum ucamara has the classic callichthyid armored-catfish build in miniature: a moderately deep, laterally compressed body covered in two overlapping rows of bony dermal plates (scutes) rather than true scales, a blunt head with a pair of sensory barbels at the mouth, and a single stout, serrated spine leading each pectoral fin. This is one of the smallest species in its genus and family — FishBase gives a maximum size of just 2 in SL, and the holotype itself was a mature 2 in SL female, confirming the species is a genuine dwarf that reaches sexual maturity at only a few centimetres.
Because it lacks true scales and instead relies on bony plating, it shares the family's sensitivity to certain medications (notably copper-based treatments), which should always be dosed conservatively. The pectoral spines, while much smaller than those of larger catfish, can still lock and catch in netting, so it is safer to guide the fish with a container than to chase it with a net.
Habitat
The species is known from the upper Amazon basin in Peru, specifically the Ucayali and Marañón river systems and the Pacaya-Samiria National Reserve in Loreto, where it occupies floodplain lakes, side channels and small creeks with dense marginal or floating vegetation. These are classic Amazonian whitewater floodplain habitats — shallow, vegetated, seasonally flooded waters that can become hypoxic (low in dissolved oxygen) as they warm and stagnate during the dry season.
Like other callichthyids, Lepthoplosternum ucamara is an obligate air-breather, regularly rising to gulp air at the surface to supplement gill respiration — an adaptation that lets it survive in the warm, oxygen-poor backwaters where it lives. Specific pH, hardness and temperature figures were not reported in the available sources; aquarists should assume warm, soft-to-neutral Amazonian floodplain conditions typical of the region rather than guessing at precise numbers.
Feeding
As a small benthic callichthyid, Lepthoplosternum ucamara is best understood as a nocturnal bottom-forager, sifting sediment and vegetation debris for small invertebrates, detritus and organic matter, much like the Corydoras species that share its range. PlanetCatfish notes that care for the dwarf hoplos of this genus mirrors that of Corydoras from the same region — benthic omnivores that do best on sinking foods.
In the aquarium it will take sinking pellets, small frozen foods and general prepared fare offered after lights-out, when this naturally crepuscular-to-nocturnal fish is most active and not out-competed by more boisterous, light-loving tankmates.
Mating
Detailed courtship observations specific to Lepthoplosternum ucamara were not found in the available sources, but the genus and subfamily are well characterised: Callichthyinae armored catfishes (Hoplosternum, Megalechis, Dianema, Callichthys and their relatives, including Lepthoplosternum) are floating bubble-nest builders. The male blows a raft of mucus-coated bubbles at the water's surface, typically anchored beneath a broad leaf or floating plant, and courts a ripe female toward it.
This places Lepthoplosternum firmly among the minority of catfish families that pair-spawn with direct male parental investment, rather than scattering eggs with no care or relying on internal fertilisation as in the unrelated driftwood catfishes.
Breeding
Lepthoplosternum ucamara is a bubble-nest builder: the male constructs a floating raft of mucus-bound bubbles at the surface, the female deposits eggs into the nest, and the male then guards and tends the clutch until the fry hatch and disperse. This basic pattern is shared across the small-bodied dwarf hoplos of the genus and makes them, in principle, genuinely breedable in a home aquarium — one of the few catfish groups covered here where that is realistically achievable rather than a commercial-only or essentially unbred proposition.
No aquarium spawning reports specific to this species were found in the cached sources, so hobbyist experience with L. ucamara itself appears to be limited; expectations should be set from the wider genus and subfamily pattern rather than species-specific accounts. A shallow, well-planted or floating-leaf setup with soft, slightly acidic-to-neutral water and stable warm temperatures would follow the pattern used for its larger relatives.
In the aquarium
The most important fact for keepers is the size trap in reverse: Lepthoplosternum ucamara stays genuinely tiny, topping out around 2 in SL, so it is one of the few armored catfishes suited to a small aquarium rather than one that will eventually demand a much larger tank. PlanetCatfish recommends the dwarf Lepthoplosternum species as a good choice for small tanks precisely for this reason, with care matching Corydoras from the same Amazonian range — a soft substrate, gentle current, and shoaling companions.
As with all callichthyids it lacks true scales and is medication-sensitive, so copper-based treatments and other harsh medications should be used conservatively or avoided. It is an obligate air-breather and needs unobstructed access to the surface. Its pectoral spines, though small, can still snag a net, so scoop it gently with a container. It is naturally most active from dusk onward, so offer food after lights-out and provide low, dense cover (leaf litter, fine-leaved plants) for daytime retreat.
Conservation
The IUCN Red List assessed Lepthoplosternum ucamara as Least Concern in an assessment dated 15 October 2020. The species is known from the Pacaya-Samiria National Reserve and the lower Ucayali River in Loreto, Peru, and appears to range more broadly through whitewater floodplain habitat across the upper Amazon in Peru and Brazil, based on FishBase distribution data.
As a small, likely under-recorded floodplain species with much of its known range falling inside a protected reserve, it does not currently face the acute pressures that threaten larger, more heavily fished or more narrowly endemic Amazonian catfishes. General Amazon floodplain concerns — habitat conversion, water-level alteration and pollution — remain the relevant long-term watch items for this and similar dwarf callichthyids.