Taxonomy & naming
Corydoras paucerna was described in 2004 by Joachim Knaack, in a paper that introduced six new corys from eastern Bolivia (alongside C. albolineatus, C. negro, C. isbrueckeri, C. noelkempffi and a sixth). The epithet is taken from the type locality, the Río Paucerna, a tributary within the Iténez (Guaporé) river basin. The species belongs to the family Callichthyidae, subfamily Corydoradinae, and was placed in Corydoras Lacépède, 1803.
The 2024 revision by Dias, Tencatt and colleagues split that overloaded genus along molecular lines. The small, slender species of the 'elegans' group were assigned to the resurrected genus Gastrodermus, and C. paucerna falls there: the current valid combination is Gastrodermus paucerna. The specialist Corydoras World, which maintains the post-2024 lineage classification, lists it within Gastrodermus, and FishBase places it there too. We keep 'Corydoras paucerna' as the heading because that is the name still familiar to the hobby, while noting the Gastrodermus placement.
Morphology
This is a very small cory, reaching only about 1.5 in in standard length — a dwarf species, among the smaller members of the genus. It has the fusiform (spindle-shaped), relatively slender body typical of the 'elegans' group rather than the deep, stocky build of the bronze cory. Fin counts are modest: a single dorsal spine with six or seven soft rays, and an anal fin with a spine and five or six soft rays.
The body carries the usual cory armour of two rows of overlapping bony scutes down each flank and a hard helmeted head, with three pairs of barbels fringing the downturned mouth. As in all corys, the dorsal, pectoral and adipose fins each bear a stiff leading spine.
Habitat
Corydoras paucerna is known from eastern Bolivia, from the Río Paucerna in the Iténez (Guaporé) basin — part of the upper Madeira system that drains the Brazilian–Bolivian Shield. Its documented range is confined to this region, with no confirmed records from elsewhere.
Detailed water-chemistry data for the type locality have not been published. Streams of the Iténez/Guaporé basin are typically warm, soft and slightly acidic, running clear or tea-stained over sand with leaf litter and submerged wood. Like other corys it is a facultative air-breather, darting to the surface to gulp air and absorb oxygen through a vascularised hindgut — an adaptation for warm, low-oxygen water.
Feeding
No dedicated diet study has been published for C. paucerna, but as a member of the Corydoradinae it is a benthic omnivore and detritivore. It works the bottom, sifting sand and fine sediment with its snout and barbels to take small invertebrates, micro-crustaceans, insect larvae, worms and organic detritus. In an aquarium a dwarf cory of this type would take finely sized sinking dried foods and small live and frozen items such as baby brine shrimp and microworm.
Mating
The reproductive behaviour of C. paucerna has not been documented, but corys are egg-laying shoalers with a conserved courtship. A ready female cleans a spawning site and the group becomes active; a male takes up the 'T-position' at right angles to her head, and a few adhesive eggs are clasped in a basket formed by her pelvic fins and pressed onto the chosen surface, the sequence repeating until the clutch is laid. The dwarf 'elegans'-group corys are expected to follow this same pattern, typically with small clutches.
Breeding
There are no captive-breeding records for Corydoras paucerna, which is essentially unknown in the hobby. If it follows its relatives, spawning would likely be cued by a cool, large water change mimicking the rainy season; the adhesive eggs would receive no parental care (adults readily eat their own spawn); and eggs would hatch in roughly three to five days, with the very small fry taking microworm and baby brine shrimp once the yolk sac is absorbed. Dwarf corys often spawn small numbers of eggs at a time and demand attentive fry care because of their size.
In the aquarium
Corydoras paucerna is not established in the trade and there is no real body of aquarium experience for it. General dwarf-cory husbandry would apply: keep it in a sizeable shoal of six or more (small corys are especially nervous in small numbers) over soft sand, which protects the delicate barbels that coarse gravel erodes. Warm, soft, well-filtered water with gentle flow and meticulous cleanliness suits the group, and tankmates must be small and peaceful — a dwarf cory can be out-competed or intimidated by anything boisterous. The usual cautions hold: fin spines can snag in a net (a cup is safer), and a stressed cory can release skin toxins dangerous in the small volume of a bag.
Conservation
Corydoras paucerna is listed by the IUCN as Data Deficient (2014) — there is not enough information to judge its extinction risk. That reflects how little is known about this small, narrowly recorded Bolivian endemic: its full distribution, population size and ecology are essentially undocumented. The Iténez/Guaporé basin remains relatively intact compared with much of the Amazon, but agricultural expansion, deforestation and changes to flow could affect the small streams such a fish depends on. With negligible collection pressure, the real need is field survey work to establish where it occurs and how it is faring.