Taxonomy & naming
Leptodoras acipenserinus was described by the German-British ichthyologist Albert Günther in 1868, and it is the type species of the genus Leptodoras — meaning every other member of the genus is defined by comparison to it. It belongs to the family Doradidae, the thorny or talking catfishes, a large South American family named for the stiff, serrated spines along the body and the audible sounds many species can produce by grinding their pectoral spines. Historically, doradid species passing through nineteenth-century taxonomy were shuffled among genera such as Doras and other early catfish groupings before the modern generic boundaries of Leptodoras were settled; the Catalog of Fishes treats Leptodoras acipenserinus as the valid combination today.
The genus name Leptodoras combines the Greek leptos, "slender" or "thin", with Doras, an older doradid genus name — an apt description of this genus's elongated build compared with the deeper-bodied doradids. The species epithet acipenserinus is Latin for "sturgeon-like", after Acipenser, the sturgeon genus, referencing the fish's long tapering body and pointed snout. The trade name "Peruvian sturgeon catfish" and local names such as "Pirillo" (Peru) and "Mandi-serra" (Brazil) echo the same resemblance.
Morphology
This is a slender, elongated catfish with a long, tapering body that narrows toward the caudal peduncle and a pointed, somewhat flattened snout — the source of its sturgeon comparison. Rows of small, bony scutes run along the flanks in typical doradid fashion, giving a plated rather than naked-skinned feel, though like other catfish it lacks true scales. The dorsal fin carries a single stiff spine followed by six soft rays (I/6), the anal fin has 9–13 rays, and a small adipose fin sits well back toward the tail. Barbels ring the mouth and help the fish feel its way over the substrate in low light.
Reported maximum size is around 8 in standard length, with total length reaching about 9.5 in in documented specimens (one voucher measured 7.5 in SL). As in other doradids, the pectoral and dorsal spines lock rigidly erect and are finely serrated — they catch in aquarium nets and can jab an unwary hand, so this fish is best moved in a container rather than netted.
Habitat
Leptodoras acipenserinus is native to the cis-Andean piedmont of the upper Amazon basin, recorded from Ecuador, Peru, Bolivia and Brazil across a wide network of rivers — the Napo, Marañón, Huallaga, Ucayali, Madre de Dios, Madeira, Guaporé (Iténez) and Paranapura among others. The type locality is Xeberos (Jeberos), near the río Aipana in Loreto, Peru.
It occupies both whitewater and blackwater river reaches, typically over sand banks and open bottom in areas of strong current, a demersal (bottom-dwelling) existence spent mostly out of sight by day. Because it ranges across both sediment-rich whitewater and tannin-stained blackwater tributaries, it is not confined to the soft, acidic conditions often assumed for Amazonian blackwater fish — it is a current-loving sand-bottom species first, with water chemistry secondary to a well-oxygenated, flowing environment.
Feeding
Leptodoras acipenserinus is a nocturnal benthic omnivore with a trophic level around 2.8, consistent with an omnivorous detritivore that forages the riverbed for small invertebrates, organic detritus and plant matter, feeling along the sand with its barbels well after dark.
In the aquarium it proves undemanding once settled, accepting sinking pellets, wafers and granules alongside frozen foods such as bloodworm, brine shrimp, mysis and chopped earthworm or market shrimp. Its barbels are sensitive, so a soft sand substrate free of sharp gravel is worth providing. Because it feeds mainly at night, offering food after the lights go out helps ensure this shy bottom-patroller gets its share in a mixed tank.
Mating
No courtship or spawning behaviour has been documented for Leptodoras acipenserinus in the wild or in captivity. Doradid catfishes as a family show varied reproductive strategies, but for this species specifically the sources consulted report reproduction as unknown.
Breeding
Breeding of Leptodoras acipenserinus has not been recorded in the aquarium, and reproductive biology is undescribed even from field studies. This mirrors many mid-sized, wild-collected Doradidae, which are imported as adults rather than propagated; there is no evidence of a bubble-nest, cavity-spawning or any other specific mode being used by this species, and none should be assumed. Anyone keeping the species should treat it as effectively unbred in the hobby and not expect fry from established tanks.
In the aquarium
Give this species room to stretch its elongated body: a minimum tank length of around 59 in is recommended, sized well beyond the footprint many keepers first picture for a 8–9.5 in catfish — the size trap that catches inexperienced buyers of "small" thorny cats. Water should run soft to moderately hard and mildly acidic to neutral, roughly pH 6.0–7.5 at 75–82 °F, with strong flow and good oxygenation echoing its sand-bank, current-swept native rivers; a fine sand substrate protects the sensitive barbels.
Like other doradids it is effectively scaleless (bony scutes aside) and therefore sensitive to copper-based and some other medications — dose conservatively, ideally at reduced strength, if treatment is ever needed. Its dorsal and pectoral spines lock rigidly and are seriously prone to tangling in nets, so always move it by herding into a container. It is peaceful, shy and strictly nocturnal, wanting caves, driftwood or dense cover to retreat into by day and calm, non-aggressive tankmates; it is not suited to nano tanks given its adult size and current requirements.
Conservation
The IUCN Red List has not evaluated Leptodoras acipenserinus, so no formal conservation status or threat assessment exists for the species (Not Evaluated). It is known from a broad span of the upper Amazon basin across four countries, which suggests a wide range, but population trends and pressures have not been formally studied.
As with many wide-ranging but poorly monitored Amazonian catfishes, general basin-scale pressures — deforestation, damming, sedimentation and unregulated fishing — are the plausible long-term concerns, though none have been specifically documented for this species. The aquarium trade appears to rely on wild-collected specimens, as no captive-breeding program has been reported.