Taxonomy & naming
Pseudocorynopoma doriae was described by the Italian naturalist Alberto Perugia in 1891, based on material from the La Plata region of South America. The valid name as recognised in Eschmeyer's Catalog of Fishes is Pseudocorynopoma doriae (Perugia, 1891); the parenthetical authority indicates that Perugia placed it in a different genus at the time of description and that it has since been assigned to Pseudocorynopoma.
Pseudocorynopoma is a small genus of characids in the family Characidae, part of the extraordinarily diverse South American freshwater fish radiation. The genus belongs to the subfamily Stevardiinae, a group notable for internal fertilisation and, in several members, for producing live young or retaining fertilised eggs — adaptations uncommon in characids generally. P. doriae is one of the better-known members of the genus, though the systematics of the group continue to be revised as molecular work clarifies relationships within the broader family.
Morphology
Pseudocorynopoma doriae is a slender, moderately elongated characid reaching up to 2.5 in standard length according to FishBase, with typical aquarium specimens usually somewhat smaller. The body is pale and translucent, with a silvery or slightly yellowish wash and a faint lateral band that may intensify under stress or during spawning. The fins are largely clear to pale.
Sexual dimorphism is pronounced. Adult males develop striking filamentous extensions on the lower rays of the caudal fin and on the posterior rays of the anal fin — the ornaments that give the fish its common name. These fin extensions are longer and more elaborate in well-conditioned males. Females are fuller-bodied, particularly when gravid, and lack the fin ornaments. The species also exhibits a feature unusual even among stevardiinae: the female retains sperm internally and can fertilise successive batches of eggs from a single mating, a form of delayed fertilisation that has practical implications in the aquarium.
Habitat
In nature, Pseudocorynopoma doriae inhabits clearwater streams and rivers across a broad arc of temperate South America, from southern Brazil south through Uruguay into the La Plata drainage of Argentina. This is a temperate to subtropical zone, distinctly cooler than the Amazonian tropics, and the fish's thermal tolerance reflects that origin.
FishBase records its preferred water conditions as 68–75 °F, pH 6.0–7.5, and general hardness up to about 20 dH. The species occupies slow to moderately flowing waters with substrates of sand or fine gravel, typically in areas with aquatic or marginal vegetation that provides cover and spawning sites. The clearwater streams of this region are generally soft to moderately hard and slightly acidic to neutral — conditions readily replicated in the aquarium.
Feeding
Pseudocorynopoma doriae is an omnivore in the wild, taking small invertebrates, insect larvae, and other zooplankton from the water column, supplemented by algae and plant material. Its slender, mid-water build suggests it feeds primarily in open water rather than at the substrate.
In the aquarium it accepts a broad diet without difficulty: quality dry foods including fine flakes and micro-pellets form a sound staple, and the fish benefits from regular offerings of small live or frozen invertebrates such as Daphnia, Cyclops, and newly hatched brine shrimp. Varied feeding improves condition and brings males' fin extensions to their best. The species is an active, alert feeder and competes well at mealtimes without being aggressive toward tankmates.
Mating
Pseudocorynopoma doriae is among the stevardiin characids that practice internal fertilisation. Males use a modified anal fin region to transfer sperm packets to the female, which can store sperm and use it to fertilise successive egg batches over an extended period — a female purchased without a male may spawn fertile eggs weeks or months after her last contact with one.
Male courtship involves displaying the ornamental caudal and anal fin extensions toward the female, often hovering alongside her and spreading the fins to full extent. The display is subtle compared with many tropical fish but unmistakable in a well-maintained group. Because sperm can be stored, hobbyists cannot always be certain whether a batch of eggs is fresh or derived from stored sperm, which adds a layer of interest to breeding these fish.
Breeding
Pseudocorynopoma doriae deposits adhesive eggs among fine-leaved plants or spawning mops, with no parental care provided after spawning; adults will consume eggs if given the opportunity and should be separated from the spawn. Eggs are small and hatch within a few days at typical breeding temperatures; the fry hang near the surface initially and require very fine first foods such as infusoria or commercial liquid fry food before graduating to newly hatched brine shrimp.
The internal fertilisation and sperm storage discussed under Mating mean that breeding groups can produce fertile spawns even without a male present at the time. Conditioning adults on a varied diet rich in live foods promotes spawning activity. A slightly reduced temperature toward the lower end of the species' range — around 68–72 °F — can trigger spawning, mimicking the seasonal cooling of the temperate South American rivers this fish inhabits.
In the aquarium
Pseudocorynopoma doriae is a peaceful, schooling fish best kept in groups of six or more in a well-planted aquarium. Its cool-water tolerance — comfortable at 68–75 °F — makes it one of the few characids suited to unheated tanks in warm temperate rooms, an asset often overlooked by hobbyists.
A tank of 23.5–31.5 in provides adequate space for a school, though larger tanks are always preferable. The species appreciates cover in the form of fine-leaved plants, floating vegetation, or spawning mops, and open water for mid-column swimming. Water should be soft to moderately hard and slightly acidic to neutral, with good filtration and regular water changes. Tankmates should be peaceful and of similar size; other cool-tolerant species such as white cloud mountain minnows or native temperate fish are natural companions, though the dragon fin tetra also works in a community with other small, undemanding tropical species kept at the lower end of their ranges. Males show their best fin ornaments in the presence of rivals or courting females, so a mixed-sex group is more interesting than a single-sex one.
Conservation
Pseudocorynopoma doriae has a broad natural distribution across temperate South America, from southern Brazil through Uruguay into the La Plata drainage of Argentina, and the species is considered of Least Concern (LC) based on available data. Its range spans multiple river systems and it tolerates a reasonably wide band of water conditions, giving it more resilience than narrow endemics.
The major stressors facing freshwater fish in this region — agricultural runoff, water abstraction, channelisation, and the introduction of exotic species — affect P. doriae as they do other stream-dwelling characids, but none of these pressures is thought to threaten the species at a rangewide level under current conditions. Most aquarium specimens are bred in captivity, which places no pressure on wild populations. The species' internal-fertilisation biology and ease of breeding in captivity make it straightforward to maintain in the hobby without wild collection.