Taxonomy & naming
Diapoma terofali was originally described by the French-Brazilian ichthyologist Jacques Géry in 1964 under the genus Glandulocauda. Subsequent revisionary work on stevardiine characids relocated the species to Diapoma, a genus erected to accommodate a cluster of small temperate South American characids now placed in the subfamily Stevardiinae of the family Characidae. The valid name as maintained in Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) is Diapoma terofali (Géry, 1964), with the parenthetical authority reflecting the original description under a different genus.
A systematic review of Diapoma published in the journal Papéis Avulsos de Zoologia confirmed the type locality as Argentina, Provincia Buenos Aires, Canal El Cazador, río Luján — a lowland coastal drainage of the lower Paraná system. That same review distinguished D. terofali from its closest congener, D. thauma, partly on gill-raker counts: D. terofali carries 11–13 rakers on the lower limb of the first arch, compared with 15–18 in D. thauma. The genus name Diapoma derives from the Greek dia (through) and poma (cover or lid), a reference to the opercular region. The species epithet honours Dr Fritz Terofal (1932–1988), ichthyologist at the Bavarian State Collection of Zoology (Zoologische Staatssammlung München) in Munich.
Morphology
Diapoma terofali is a small, elongate characid reaching approximately 2.5 in standard length. The body form is typical of stevardiine characids: moderately slender and laterally compressed, with the body deepest just ahead of the dorsal fin and tapering to a narrow caudal peduncle. The head is small and pointed. Like other members of Diapoma, it lacks the bold patterning of many aquarium tetras and has a relatively plain silvery appearance.
The distinguishing meristic character within the genus is the gill-raker count on the lower limb of the first gill arch: D. terofali consistently shows 11–13 rakers, setting it apart from D. thauma with its higher count of 15–18. Beyond that, detailed morphometric and meristic data are sparse in the accessible literature, which reflects the group's status as a taxonomically modest, regionally studied genus rather than a widely profiled aquarium fish.
Habitat
The species is distributed across the lower Paraná and Uruguay River basins of south-eastern South America, a broad lowland region encompassing parts of Argentina, Uruguay, and southern Brazil. The type locality — Canal El Cazador in the río Luján drainage of Buenos Aires Province — typifies the habitat: lowland coastal streams and canals in the temperate Pampas region, with neutral pH and relatively cool water compared with the tropical streams that host many other characid species.
FishBase classifies D. terofali as benthopelagic, indicating it occupies the lower water column as well as the middle levels of standing and slow-flowing water. The broader Diapoma genus review associates the genus with temperate freshwater habitats in lowland drainages of the southern cone, where seasonal temperature swings are considerable and water chemistry tends toward neutral to slightly alkaline.
Feeding
No detailed dietary study of Diapoma terofali in the wild appears in the accessible literature. By analogy with other small stevardiine characids of similar size and habitat, the species is presumed to be an opportunistic micro-predator and omnivore, feeding on small aquatic invertebrates, insect larvae, microcrustaceans, and incidentally on plant material or algae.
In the aquarium, Diapoma terofali and its congeners are reported to accept standard small-particle prepared foods — fine flake, micro-pellets — as well as small live and frozen invertebrates such as Daphnia, brine shrimp nauplii, and Cyclops. Providing a varied diet with a live or frozen component is recommended to maintain condition.
Mating
Diapoma terofali is an egg-scattering species with no parental care, consistent with the reproductive mode documented across Stevardiinae and the broader Characidae. Courtship behaviour in the genus is not described in detail in the available literature. Males of stevardiine genera are typically distinguished by secondary sexual characters such as hook-like spines on the anal-fin rays or glandular tissue, which play a role in courtship; whether D. terofali shows prominent secondary characters is not confirmed in the accessible sources.
As with most small egg-scattering characids, spawning is presumed to involve brief courtship chases among fine-leaved vegetation or other substrate, with the pair releasing eggs and milt simultaneously before separating. Eggs are not guarded.
Breeding
Diapoma terofali has been bred in aquaria, and its breeding mode is that of a typical egg-scattering characid with no parental care. Adults scatter adhesive or semi-adhesive eggs among fine-leaved plants or over other substrate; the eggs are not guarded and will be eaten by the parents if not removed.
Specific data on clutch size, incubation time, and fry rearing for this species are not documented in the accessible literature. General stevardiine practice would suggest conditioning adults with live and frozen foods, using a densely planted breeding tank or spawning mops, and removing adults after spawning. Fry are presumed to be small and may require infusoria or similarly fine first foods before graduating to newly hatched brine shrimp. As a temperate species, it is likely tolerant of somewhat cooler breeding temperatures than tropical tetras.
In the aquarium
Diapoma terofali is not commonly encountered in the aquarium trade outside of South America, and availability in the broader hobby is limited. When kept, it does best as a schooling species in a group of six or more individuals, in a well-planted aquarium with gentle to moderate flow and neutral, moderately soft to moderately hard water. As a temperate fish from the southern cone, it tolerates and may benefit from cooler temperatures than most aquarium tetras — conditions in the low-to-mid 20s Celsius are appropriate, and warmer tropical temperatures are best avoided.
Its subdued colouration and modest size make it a fish for the specialist rather than the general community aquarium. It is compatible with similarly sized, peaceful species that share its temperate preference. Standard small-particle foods and clean, well-oxygenated water are the key requirements. Data on longevity in captivity are not available in the literature.
Conservation
Diapoma terofali was assessed as Least Concern (LC) on the IUCN Red List in 2021, indicating that the species does not approach the thresholds for a threatened category. The assessment, published as version 2025-2 (assessment ID 167669), reflects a species with a reasonably wide distribution across the lower Paraná and Uruguay drainages — large, well-connected river systems — without evidence of population-level decline severe enough to warrant an elevated listing.
That said, the lower Paraná basin faces ongoing pressure from agricultural runoff, urbanisation (particularly around Buenos Aires Province where the type locality lies), water extraction, and channelisation of small coastal drainages. Small stevardiine characids in modified lowland streams can be locally affected by such changes even when the species remains broadly stable. No specific conservation measures are documented for D. terofali, and ongoing monitoring of lowland stream communities in the southern cone remains important for detecting changes in species like this that attract little commercial or hobbyist attention.