Taxonomy & naming
Tyttobrycon marajoara was described by Marinho, Bastos & Menezes in 2013 from material collected in the Marajó river basin, state of Pará, Brazil. The species belongs to the genus Tyttobrycon, a group of small characins within the family Characidae. Eschmeyer's Catalog of Fishes recognises the valid name as Tyttobrycon marajoara Marinho, Bastos & Menezes, 2013.
The genus name Tyttobrycon derives from the Greek tyttos (small or little) combined with brycon (a biter, from bryo, to bite or to be full), broadly used as a suffix for characins throughout the Amazon basin. The species epithet marajoara is a toponym and cultural reference honouring Marajó Island and the Marajó river basin of Pará, the type locality, and recalls the Marajoara culture, an ancient ceramics tradition of the region. Together, the name conveys 'the small characin of Marajó'.
Morphology
Tyttobrycon marajoara is a very small characid, with a maximum recorded standard length of 1 in in males or unsexed individuals. Like others in the genus it has the typical slender, laterally compressed body plan of small Amazonian characins, with the characid hallmarks of an adipose fin and a toothed premaxilla.
Detailed morphological data for this species are sparse in the hobbyist literature. As a member of a genus of miniature characins, it likely shows the subtly forked tail, moderate eye diameter, and relatively large mouth relative to body size that characterise many small characids exploiting invertebrate prey in still or slow-moving forest-edge waters. Coloration is not thoroughly documented in accessible sources; data sparse.
Habitat
Tyttobrycon marajoara is known from the Marajó river basin in the state of Pará, in the eastern Amazon drainage of Brazil. Marajó Island and the surrounding drainage represent a low-lying, seasonally flooded mosaic of freshwater channels, igapó forest, and várzea wetlands at the mouth of the Amazon system.
As a small characin from this region, it likely inhabits shallow, slow-moving to standing water — forest-margin pools, flooded vegetation margins, and blackwater or clearwater side channels. Specific water-chemistry records for the Marajó basin typically indicate warm temperatures consistent with lowland equatorial Amazonia and variable pH influenced by seasonally fluctuating floodwaters. Precise field measurements for this species' microhabitat are not available in widely accessible sources.
Feeding
No specific dietary studies of Tyttobrycon marajoara are documented in accessible literature. Small characins of this size class in the Amazon are broadly invertivorous, feeding on microcrustaceans, small insect larvae, and other zooplankton in the water column and at the surface film.
In the aquarium, comparably sized miniature characids generally accept small live and frozen foods such as newly hatched brine shrimp, micro-worms, and Daphnia, as well as finely crushed quality dry foods. Given the species' small adult size, food particle size is a practical consideration: items must be appropriately tiny to be taken readily.
Mating
No published mating observations specific to Tyttobrycon marajoara are available in accessible sources. Small characins of this type are generally egg-scattering open spawners; males likely court females with fin displays and active pursuit, with no pair bond formed and no territory maintained between individuals.
Spawning is expected to involve the scatter of adhesive eggs among fine-leaved aquatic plants or submerged vegetation, as is typical for the broader characid guild. No parental care of eggs or fry is expected in this group; adults do not guard or tend the spawn.
Breeding
Breeding has not been documented in the accessible hobbyist or scientific literature for this species. Based on the biology of related small Amazonian characins, spawning would likely consist of the scattering of small adhesive eggs over fine-leaved plants or a substrate of soft vegetation, with the adults offering no subsequent parental care.
Incubation period and fry development data are not available. As with other miniature characids, fry would be expected to be very small at hatching and would require appropriately sized first foods. Because the species is not established in the ornamental trade to any documented extent, captive-breeding experience is lacking.
In the aquarium
Tyttobrycon marajoara is not known to be present in the ornamental fish trade and has no established hobbyist literature. Its very small adult size of around 1 in SL would place it among the nano-sized characins appropriate only for small, dedicated species aquaria or carefully chosen nano community setups with equally small, non-predatory tankmates.
Any aquarist who obtains this species should research the water conditions of its native Marajó basin drainage — soft, warm, slightly acidic to neutral Amazonian water is a reasonable starting point. A densely planted aquarium with gentle filtration and subdued lighting would suit a fish accustomed to the shaded, vegetated margins of Amazonian flood-forest habitats. Data on specific husbandry requirements are sparse.
Conservation
Tyttobrycon marajoara is assessed as Least Concern (LC) on the IUCN Red List, with the assessment completed on 07 November 2018. The Least Concern listing indicates that, at the time of assessment, the species did not meet the threshold criteria for a threatened or near-threatened category.
The Marajó river basin, while part of a globally significant Amazonian wetland system, faces ongoing pressures from land-use change, deforestation, and drainage of seasonally flooded habitats. The restricted basin-level range of this species means that localised habitat changes could affect populations; however, detailed threat analysis for this microendem is not available in widely accessible sources. Continued monitoring of lowland Amazon floodplain habitats across Pará remains important for small-range endemics of this kind.