Taxonomy & naming
Poptella fortispina was formally described by Garcia-Ayala and Benine in 2023 in the journal Neotropical Ichthyology (volume 21, issue 1, article e220086). The holotype, INPA 59843, is a specimen of 2 in standard length (SL) collected from the igarapé Cobal in the rio Xingu basin, Pará state, Brazil (approximately 03°23'S 51°75'W). The species belongs to the genus Poptella Eigenmann, 1908, within the family Characidae, and its valid name per the Catalog of Fishes is Poptella fortispina Garcia-Ayala & Benine, 2023.
The species is diagnosed within Poptella by a combination of characters centred on the predorsal spine: that structure in P. fortispina is notably robust, thick, and curved downward, in contrast to the more slender spines of congeners. Meristically, it carries 15–18 scale rows around the caudal peduncle, distinguishing it from the 13–14 rows found in other members of the genus, and possesses 9 branched dorsal-fin rays rather than the 10–11 seen in P. brevispina, P. longipinnis, and P. fuscata. With this addition, Poptella contains seven valid species.
Morphology
Poptella fortispina is a small, laterally compressed characid with a standard-length range of 1–2.5 in in the type series, with the holotype measuring 2 in SL. Like all members of the genus it has the general body plan typical of small schooling characids: a rounded lateral profile, a moderate body depth, and a forked caudal fin.
The species' defining character is its predorsal spine, which is unusually strong and thick relative to those of other Poptella species, and curves noticeably downward — an unusual configuration within the genus. Scale counts around the caudal peduncle (15–18 rows) and the reduced branched dorsal-fin ray count (9, versus 10–11 in the closest congeners) provide additional hard meristic characters that support its distinctness. The overall colour pattern in preserved material is unreported in detail in the primary description, but the body form and proportions are consistent with the small-bodied, silvery schooling characid aspect shared by its congeners.
Habitat
The type series was collected from the igarapé Cobal and associated waters within the rio Xingu basin, spanning Pará and Mato Grosso states in Brazil. Igarapés are small, forested headwater streams typical of Amazonian terra firme; they characteristically run over sandy or leaf-littered substrates shaded by dense gallery forest, carry soft, acidic, poorly mineralised water, and experience seasonal fluctuations in volume and temperature driven by Amazonian wet and dry cycles.
The broader rio Xingu basin is one of the most biodiverse river systems in the Amazon, with strong endemism in its middle and lower reaches. No detailed in-situ habitat or water-chemistry data for the collection sites of P. fortispina are provided in the original description, so specific temperature, pH, or conductivity figures for this species' native waters cannot be confirmed from available sources. The Xingu's headwater igarapés are generally warm, soft, and acidic, consistent with other Amazonian interior drainages.
Feeding
No specific dietary data have been published for Poptella fortispina, and the diet has not been examined in the original description. Based on the feeding ecology documented for other small characids of similar body size and habitat — including other Poptella species — the species is presumed to be an opportunistic omnivore, taking small aquatic and terrestrial invertebrates, micro-crustaceans, insect larvae, and plant or algal material available in the water column and at the surface.
In an aquarium context, small Poptella characids readily accept dried foods of appropriate size — fine-grade flake and small pellets — along with frozen or live items such as Daphnia, small brine shrimp, and Cyclops. Providing a varied diet supports general health and condition, as is true of virtually all small characids in captivity.
Mating
No observational data on the mating behaviour of Poptella fortispina have been published. As a small, schooling characid in the family Characidae, it almost certainly follows the egg-scattering, open-water or plant-associated spawning strategy typical of the group: males court females in the water column or among vegetation, with no territory formation or nest building, and eggs are released and fertilised in open water or deposited among fine-leaved plants.
In related small characids, spawning activity is often triggered by water changes and a slight drop in temperature, mimicking the onset of the rainy season. Males may display actively to females by circling or lateral positioning before a brief spawning rush among vegetation or surface cover. No specific observations exist for this species.
Breeding
Poptella fortispina has not been reported in the aquarium hobby and its breeding in captivity has not been documented in the available literature. Based on the reproductive biology of small South American characids generally, it would be expected to be an egg-scatterer with adhesive or semi-adhesive eggs deposited among fine-leaved plants or spawning mops, with no parental care and a tendency for adults to consume eggs if not removed.
Should the species become available in the hobby, standard small-characid breeding protocols — conditioning adults on live and frozen foods, performing a partial water change to trigger spawning, providing dense fine-leaved vegetation or synthetic mops as a spawning medium, and separating adults from eggs — would be a reasonable starting point. Incubation times and fry requirements are unknown but, by analogy with other small Amazonian characids of similar size, eggs would be expected to hatch within 24–48 hours at warm temperatures, with fry requiring very fine foods initially.
In the aquarium
Poptella fortispina is not known to be established in the aquarium hobby as of 2023–2024. It was described from museum material and research collections, and no husbandry accounts have been published. Should specimens become available, the species would likely be kept similarly to other small Amazonian characids: in a group in a well-filtered, planted aquarium with soft, slightly acidic to neutral water at Amazonian temperatures (approximately 75–82 °F), with a varied diet of fine dried and live or frozen foods.
Its small size (under 2.5 in SL) and presumed peaceful schooling disposition would make it suitable for a community of similarly scaled fishes from soft-water South American biotopes. The species' rarity and lack of trade presence mean that practical husbandry guidance remains to be established by first-hand keepers.
Conservation
The authors of the original description evaluated Poptella fortispina against IUCN Red List criteria and recommended a status of Least Concern (LC), finding no imminent threats detected in the area of occurrence at the time of description. The assessment was conducted against the IUCN Standards and Petitions Subcommittee (2022) guidelines.
The species is currently known only from the rio Xingu basin in Pará and Mato Grosso, Brazil. While its restricted known range from a small number of Xingu headwater igarapés warrants monitoring, the Xingu drainage is a large system and the species may occur more broadly than the type series suggests. Large-scale threats to Amazonian river systems — deforestation, agricultural runoff, and hydrological alteration — remain relevant background pressures on all small stream-dwelling endemics in the basin, even those not currently regarded as threatened.