Taxonomy & naming
Poptella brevispina was described by the Brazilian ichthyologist Roberto E. Reis in 1989. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) records the valid name as Poptella brevispina Reis, 1989, and it remains placed in the genus Poptella within the family Characidae. Poptella is a small New World genus of laterally compressed, schooling characids distributed across the Amazon, Orinoco, and Paraguay–Paraná drainages of tropical and subtropical South America.
The genus Poptella was erected by Eigenmann in 1908, and its members have historically been placed in the subfamily Stethaprioninae alongside other deep-bodied, silvery characins. Relationships within the group have been revised several times as phylogenetic methods have improved, and the limits and composition of the subfamily remain the subject of ongoing work. P. brevispina has not been revised since its original description, and its relationships to the other three or four species recognised in the genus — including the widespread P. compressa and P. orbicularis — have not been resolved by a published cladistic analysis.
Morphology
Poptella brevispina is a small to moderately sized characid, laterally compressed and moderately deep-bodied in the manner characteristic of the genus. The specific epithet brevispina — from the Latin brevis (short) and spina (spine) — refers to the reduced or fewer dorsal-fin spines that distinguish this species from its congeners and were the primary diagnostic character noted at the time of description.
The overall colour is silvery, with the flanks catching light in the manner of many open-water schooling characids. A lateral stripe or humeral spot may be present as in related species; precise meristic and morphometric data beyond what is encoded in the original description are not widely published in accessible literature. The species is unlikely to exceed about 3–4 in standard length, consistent with the size range seen in other Poptella, though reliable maximum-size data are not available in the sources consulted.
Habitat
Poptella brevispina occurs in the Rio Paraguay basin, which drains the vast Pantanal wetland system of western Brazil, eastern Bolivia, and Paraguay — one of the world's largest tropical flooded savannahs. Within this system, characids of the genus Poptella are associated with slow-flowing or still, often turbid waters of the lowland floodplain: rivers, lakes, oxbows, and seasonally flooded grasslands.
Water conditions in the Paraguay basin floodplain are warm and typically slightly acidic to neutral, with low to moderate conductivity, though values shift considerably across the seasonal flood pulse that defines Pantanal hydrology. During the wet season, fish disperse widely across inundated floodplain habitats; as waters recede, populations concentrate in residual water bodies. Like many open-water characids, P. brevispina is likely to be a mid-water schooling species rather than a substrate-associated one. Detailed field ecology specific to this species has not been published in the accessible literature.
Feeding
No published feeding study specific to Poptella brevispina is available in the sources consulted. Based on the ecology of congeners and similarly positioned mid-water characids in South American floodplain systems, the species is expected to be an opportunistic omnivore, consuming small invertebrates — aquatic insect larvae, microcrustaceans, and similar zooplankton — along with organic detritus and plant material suspended in the water column.
In the aquarium, related Poptella species adapt readily to prepared foods including good-quality flake, micro-pellets, and small frozen foods such as Daphnia, Cyclops, and brine shrimp nauplii. A varied diet that supplements dry foods with small live or frozen invertebrates is likely to maintain condition in P. brevispina, consistent with what is reported for its congeners.
Mating
No specific observations on the mating behaviour of Poptella brevispina have been published. Members of the genus Poptella are egg-scattering characids, and the available evidence for the group is consistent with the standard characid pattern: non-adhesive or slightly adhesive eggs broadcast among fine-leaved aquatic plants or over the substrate, with no parental care and a risk of egg predation by the spawning adults themselves.
In floodplain-dwelling South American characids, spawning is commonly triggered by rising water levels and the associated temperature and chemical cues of the wet season, which flood new habitats and provide shelter for eggs and fry. Whether P. brevispina follows a similarly seasonal pattern has not been specifically documented.
Breeding
Poptella brevispina has not been reported as bred in the aquarium in the available literature. Given the egg-scattering mode expected for the genus, captive breeding — if achieved — would likely follow the approach used for similar open-water characids: a separate, well-planted or mop-equipped breeding tank, a small group of well-conditioned adults, and removal of adults after spawning to prevent egg predation.
Eggs of small to medium characids typically hatch within 24–72 hours at tropical temperatures, and the resulting fry require very fine first foods — infusoria or commercial fry preparations — before progressing to newly hatched brine shrimp. No specific data on incubation time, fry size, or larval development are available for this species.
In the aquarium
Poptella brevispina is not a regularly traded aquarium species and is rarely, if ever, encountered in hobby literature or commercial stock lists. It may occasionally appear in shipments of wild-caught Pantanal fish or mixed characid collections, but it has not become an established aquarium subject in the way that some of its congeners — notably P. compressa — have.
Were it to be kept, an aquarium approach appropriate for similarly sized, mid-water Paraguayan characids would apply: a spacious tank with a long swimming lane, warm soft to moderately hard water (around 75–82 °F, pH 6.5–7.5), a school of at least six individuals to express natural behaviour, and a varied diet. The genus as a whole is peaceful in mixed communities. The near-absence of hobbyist records means that specific advice on keeping this species must be extrapolated from congeners rather than drawn from documented experience.
Conservation
Poptella brevispina has not been formally assessed for the IUCN Red List and is currently listed as Not Evaluated (NE). No species-specific conservation data have been published in the sources consulted. The broad distribution of the species within the Rio Paraguay basin, including the Pantanal, means it is unlikely to face the same acute range-restriction pressures as endemics of small lake systems, though Pantanal habitats face ongoing threats from agricultural conversion, water diversion, and the expansion of soy and cattle ranching across the catchment.
The Pantanal as a whole is recognised as a globally significant freshwater biodiversity hotspot, and the fish fauna it supports — including poorly known species such as P. brevispina — benefits indirectly from conservation attention directed at the broader system. A formal IUCN assessment would require current distribution data and population trend information that have not, to this author's knowledge, been compiled for this species.