Taxonomy & naming
Thrissobrycon pectinifer was described by the American ichthyologist James E. Böhlke in 1953. The type locality is the upper Rio Negro at Cucuhy (São Antonio), Brazil, near the Venezuelan border. Eschmeyer's Catalog of Fishes records the valid name as Thrissobrycon pectinifer Böhlke, 1953, with no subsequent synonymy of note.
The genus Thrissobrycon is a small and poorly studied characid genus within the family Characidae. It was erected to accommodate a compact cluster of small South American characins sharing certain scale and fin characters; the genus has received limited modern phylogenetic attention, and its precise placement within the broader characid radiation is not fully resolved. T. pectinifer is one of very few accepted species in the genus, and detailed comparative work at the genus level remains sparse in the published literature.
Morphology
Thrissobrycon pectinifer is a small, slender characid. Detailed meristic and morphometric data for this species are sparse in the accessible literature beyond the original description, but members of Thrissobrycon share the general body plan common to many small Amazonian characins: a compressed, elongate-to-moderately deep body, a small terminal mouth, a complete lateral line, and the adipose fin that is the hallmark of the family.
The specific epithet pectinifer, from the Latin for 'comb-bearing', refers to a feature of the dentition or scale structure noted in the original description — a useful reminder that Böhlke's 1953 diagnosis was grounded in structural detail. Precise maximum size data were not accessible from the pre-crawled sources; based on the body plan typical of the genus, the species is believed to be small, likely under 2 in standard length, but this figure should be treated as provisional until confirmed by primary literature.
Habitat
The type locality places Thrissobrycon pectinifer in the upper Rio Negro, and the species is also recorded from the Orinoco basin of Colombia and Brazil. The upper Rio Negro is a blackwater river draining the Guiana Shield, with acidic, tannin-stained waters. Its tributaries encompass a range of habitat types, from fast-flowing, well-oxygenated montane streams to slow, blackwater or whitewater lowland channels fringed with flooded forest.
No habitat-specific data for T. pectinifer are available from the sources captured in this survey. By analogy with other small characids of the upper Amazon basin, the species likely occupies vegetated margins of slow-moving or still waters, or shallow forest streams and flooded areas where leaf litter and submerged roots provide cover and foraging substrate. Detailed water-chemistry records for the specific collection site of the type specimens have not been located.
Feeding
No dietary data specific to Thrissobrycon pectinifer are available from the sources surveyed. Small Amazonian characids of comparable body plan are generally opportunistic feeders, taking small aquatic invertebrates, terrestrial insects falling onto the water surface, micro-crustaceans, and organic detritus. It is reasonable to infer a similar omnivorous tendency in T. pectinifer, but this remains extrapolation from the broader family rather than direct observation.
In the aquarium, should the species become available, a diet of good-quality small prepared foods supplemented with live or frozen micro-invertebrates — Daphnia, Artemia nauplii, micro-worms — would be appropriate for a fish of this size class.
Mating
No mating observations for Thrissobrycon pectinifer have been published in the accessible hobby or scientific literature. The species has not been reported in the aquarium trade, and no captive-breeding accounts have been located.
By analogy with closely related small characids, T. pectinifer would be expected to practise open egg-scattering spawning over fine-leaved plants or substrate, with adhesive or semi-adhesive eggs and no parental care. This inference is based on the general reproductive mode of the broader Characidae and should not be taken as confirmed species-specific data.
Breeding
Thrissobrycon pectinifer has not been reported as bred in captivity, and no breeding accounts appear in the accessible literature. Given its apparent rarity in the trade, the reproductive biology of this species remains essentially undescribed in practical terms.
Aquarists encountering the species for the first time would likely approach breeding following the standard small-characid protocol: a well-conditioned group, a separate breeding tank with fine-leaved plants or spawning mops, slightly warmer and softer water to trigger spawning, and removal of adults after egg deposition to prevent predation. Incubation and fry care would follow the pattern typical of egg-scattering characids, with very small first foods required at hatching.
In the aquarium
Thrissobrycon pectinifer is essentially unknown in the aquarium hobby. It does not appear in mainstream trade lists, and no husbandry accounts have been published. The species is known from scientific collections and the ichthyological literature, and any appearance in the hobby would represent an exceptional import of wild-caught specimens from the upper Rio Negro region.
Were it to become available, the general care requirements expected for a small Amazonian characid would apply: a well-maintained planted aquarium, soft to moderately hard water at tropical temperatures, a peaceful community of similarly sized fishes, and a varied diet of small foods. Its small size and presumed peaceful temperament would make it suitable for a species tank or a quiet community setting. Aquarists interested in this genus should regard available husbandry literature as absent and be prepared to adapt from first principles.
Conservation
Thrissobrycon pectinifer has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated (NE). The species' small distributional footprint — known from the upper Rio Negro and Orinoco systems — and its near-total absence from monitoring programmes and the aquarium trade mean that population trends and threat levels are unknown.
The drainages it inhabits face the pressures common to much of Amazonia — deforestation, mining, and infrastructure development — which degrade stream and floodplain habitats. Whether T. pectinifer is locally common and simply uncollected, or genuinely restricted and potentially vulnerable, cannot be determined from existing data. A formal assessment supported by targeted field surveys would be the most useful first step in understanding this species' conservation position.