Taxonomy & naming
Phenacogaster wayampi was described by Le Bail and Lucena in 2010, with the type locality in the Ouaqui River drainage of French Guiana. The genus Phenacogaster belongs to the family Characidae and is placed within the diverse assemblage of small Neotropical tetras that radiate across South American lowland river basins from the Orinoco to the La Plata. Eschmeyer's Catalog of Fishes is the authority for the valid name Phenacogaster wayampi Le Bail & Lucena, 2010.
The genus Phenacogaster comprises roughly two dozen species of small, often transparent or translucent characins. Members are characterised by their elongate, compressed bodies, a well-developed lateral line, and often a distinct humeral spot and mid-lateral stripe. Several species are sympatric across the Guiana Shield region, and accurate identification requires close attention to meristics and pigmentation pattern. The species epithet wayampi references the Wayampi (Wayãpi) people, an indigenous Tupi-Guarani group inhabiting the upper Oyapock River region of French Guiana and Brazil — a naming tradition in French Guianan ichthyology that honours the peoples of the interior.
Morphology
Phenacogaster wayampi is a small, slender characin typical of the genus. Members of Phenacogaster generally reach 1–2.5 in standard length, and P. wayampi is expected to fall within this range; precise maximum size data for this species are sparse given its recent description. The body is laterally compressed and moderately elongate, with a somewhat pointed snout and a terminal or slightly upturned mouth adapted for feeding in open water.
Coloration in Phenacogaster species is typically translucent to silvery, often with a dark mid-lateral stripe running from behind the humeral spot to the base of the caudal fin, and a distinct caudal spot. The humeral spot — a dark blotch behind the operculum — is a genus characteristic shared by most species. Fin pigmentation is usually minimal, though breeders and displaying males in some Phenacogaster may show a slight reddish or yellowish flush to the unpaired fins. Definitive meristic and pigmentation data specific to P. wayampi are best obtained from the original description.
Habitat
Phenacogaster wayampi is known from the Ouaqui River drainage, a tributary system in French Guiana that drains the interior of the Guiana Shield. The rivers of French Guiana's interior are characteristically clear to slightly tannin-stained, flowing over granitic or sandy substrates through dense tropical rainforest. Water is warm, soft, and moderately to strongly acidic in these upland shield drainages, reflecting the geology of ancient Precambrian rocks with low buffering capacity.
Like other Phenacogaster recorded from Guiana Shield waters, P. wayampi likely inhabits the mid-water column of slower stream reaches, backwaters, and flooded margins, where it can be found among submerged roots and woody debris as well as in open water. Seasonal flooding and the resulting expansion of available habitat are characteristic of Neotropical lowland ichthyofaunas, and the species probably exploits forest-inundated margins during high-water periods.
Feeding
Phenacogaster species are opportunistic carnivores to omnivores in the wild, feeding primarily on small aquatic and terrestrial invertebrates taken from the water column and surface film. Typical prey items for small characins of this type include microcrustaceans, insect larvae, small insects falling onto the water surface, and, to a lesser extent, algae and detritus ingested incidentally.
In the aquarium, Phenacogaster are undemanding feeders that accept most small prepared foods — quality flake and micropellets are readily taken — alongside live and frozen foods such as brine shrimp nauplii, Daphnia, and Cyclops. A varied diet with a live-food component improves condition and encourages natural behaviour. The species' small mouth size limits it to finely sized foods.
Mating
No specific mating observations for Phenacogaster wayampi have been published. The genus as a whole is presumed to follow the generalized characid pattern of open egg-scattering with no pair bond and no parental care. In related Phenacogaster species, males may exhibit slightly more intense fin coloration and a slimmer body profile compared with gravid females, but reliable dimorphism data for this species are not available.
Spawning behaviour in Phenacogaster is expected to involve brief chasing and side-by-side swimming as the pair releases eggs and milt simultaneously into fine-leaved vegetation or open water, after which the adults disperse. The adhesive or semi-adhesive eggs settle among plants or substrate debris. Males from social groups in aquaria may display laterally to one another, intensifying any available body colour.
Breeding
Phenacogaster wayampi has not been documented in aquarium breeding reports in the available literature. By analogy with the genus and family, breeding would be expected to follow the standard characid model: egg-scattering over fine-leaved plants or a spawning mop, with eggs released in small numbers during a spawning bout, no parental care, and the adults likely to consume any eggs within reach after spawning.
Conditioning adults on live and varied foods, maintaining soft and slightly acidic water consistent with the species' French Guiana origin, and providing fine-leaved spawning substrate would be the recommended approach if attempting captive propagation. Fry are expected to be small and to require fine first foods such as infusoria or commercial liquid fry preparations before graduating to newly hatched brine shrimp. Data-sparse species in this genus often breed without difficulty once the correct triggers are supplied.
In the aquarium
Phenacogaster wayampi is not established in the mainstream aquarium hobby and is unlikely to be encountered outside of specialist collections or imports of mixed French Guianan characins. If available, it would suit a small species aquarium or a biotope aquascape mimicking the Guiana Shield's dark, soft, acidic streams: tannin-stained water, sandy or fine-gravel substrate, driftwood, dried leaf litter, and subdued lighting.
As a small, shoaling characin, it should be kept in groups of six or more to promote natural behaviour and reduce individual stress. Water chemistry should lean soft and acidic — pH in the 5.5–7.0 range and low hardness — and temperatures in the 73–82 °F range consistent with French Guiana lowland streams. Tankmates should be similarly small and peaceful; other Guiana Shield micro-tetras, small pencilfish, dwarf cichlids, and small Corydoras are compatible choices. The species is best treated as delicate on import and allowed time to acclimate to aquarium conditions before being mixed with more competitive species.
Conservation
Phenacogaster wayampi has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated (NE). Its known range is restricted to the Ouaqui River drainage of French Guiana, which places it among the narrowly endemic elements of the Guiana Shield ichthyofauna. French Guiana retains extensive intact primary forest, and the interior drainages experience relatively low levels of direct human disturbance compared with many other parts of the Amazon and Guiana Shield regions.
However, the restricted known range of P. wayampi and the general threats facing Guiana Shield ichthyofaunas — gold mining (orpaillage) with associated mercury contamination and sedimentation, and forest clearance — mean the species warrants monitoring. A formal IUCN assessment would require survey data on its actual distribution width and population status. Until such data are gathered, the precautionary approach is to treat it as potentially sensitive to catchment-level disturbance.