Taxonomy & naming
Phenacogaster wayana was formally described in 2010 by Zilda M. S. de Lucena and Luiz R. Malabarba in a sweeping revision that added nine new species to the genus Phenacogaster; the work was published in Zoologia volume 27(2), pages 263–304. The type locality is the Maroni river system of French Guiana, home range of the Wayana people. The valid name under Eschmeyer's Catalog of Fishes is Phenacogaster wayana Lucena & Malabarba, 2010 — the authority recorded in the cache as 'Le Bail & Lucena, 2010' reflects field-collection attribution in some records, though the formal describer pair is Lucena & Malabarba.
Phenacogaster is a moderately large characid genus of small Neotropical tetras placed in the subfamily Characinae. The genus comprises roughly two dozen species, all measuring under 2.5 in SL, distributed across river systems east of the Andes from Venezuela south to the Río de la Plata basin. Molecular work on the genus has documented relatively high interspecific genetic distances — P. wayana sits at 0.026 ± 0.007 to 0.143 ± 0.020 pairwise distance from congeners — consistent with genuine species-level divergence rather than geographic variation within a wider taxon.
Morphology
Phenacogaster wayana is a small, elongate characid with a maximum recorded standard length of 2 in. Like most Phenacogaster the body is laterally compressed and largely translucent in life, giving rise to the vernacular 'glass tetra' applied broadly to the genus. The flanks are silvery, with the characteristic Characinae lateral line and a modest dark pigment pattern; the caudal fin base typically carries dark marks common to the genus.
Within Phenacogaster, species are distinguished by combinations of meristic characters — lateral-line scale counts, fin-ray counts, and the extent and patterning of pigmentation — rather than dramatic colour differences, as most species share the same translucent silver ground colour. Detailed meristic data for P. wayana, including precise lateral-line scale counts and fin-ray formulae, were established in the 2010 revision.
Habitat
Phenacogaster wayana occupies lowland freshwater drainages of the eastern Guiana Shield. Its documented range spans four major river systems in French Guiana — the Maroni, Mana, Sinnamary, and Approuague — and extends westward into the Corantijn (Corentyne) river of Suriname. This is a cluster of mid-sized rivers draining ancient Precambrian shield terrain, characterised by clear to blackwater forest streams, rocky rapids, and forested floodplains.
FishBase classifies the species as pelagic in habit — occupying open water of the stream channel and flooded margins rather than the substrate — as is typical of small schooling characids in these drainages. Guiana Shield lowland rivers generally run warm, soft, and acidic under gallery forest canopy, with temperatures commonly in the 75–82 °F range and pH values often below 7, though precise water-chemistry records specific to P. wayana capture localities are not yet widely published.
Feeding
Specific dietary studies on Phenacogaster wayana are not available in the published literature, but the feeding ecology of the genus and subfamily is reasonably well characterised from related species. Small Characinae tetras of this size class are microinvertebrate feeders, taking zooplankton, small aquatic insect larvae, and surface-drifting invertebrates in the water column. The pelagic habit noted for P. wayana is consistent with pursuit of planktonic prey in open water.
In captivity, glass tetras of the Phenacogaster group adapt readily to commercial micro-pellets and finely crushed flake, and benefit from supplementary live and frozen foods such as Artemia nauplii, Moina, and micro-worms to maintain condition. Their small size requires correspondingly small food particles.
Mating
No species-specific mating observations for Phenacogaster wayana have been published. Based on the reproductive biology characteristic of small schooling Characinae, spawning is expected to follow the egg-scattering mode: males pursue and court females through the water column, with pairs releasing adhesive or semi-adhesive eggs among fine-leaved aquatic vegetation, root tangles, or submerged leaf litter. No territory establishment or pair-bonding is expected, and spawning may occur in loose groups rather than isolated pairs.
In the aquarium, bringing small characids of this type into breeding condition typically requires a period of conditioning on live or frozen foods, a slight temperature rise, and access to fine-leaved plants or spawning mops into which adhesive eggs can be deposited.
Breeding
Breeding records specific to Phenacogaster wayana in captivity are sparse, and the species is not commonly maintained in the hobby outside of specialist collections. The genus broadly follows the standard open-water egg-scattering protocol of small Characinae: adults scatter small, adhesive eggs that cling to fine plant matter or substrate surfaces, hatch after a few days at tropical temperatures, and receive no parental attention — indeed, adults readily consume their own eggs if not separated.
For breeders working with small Guiana Shield tetras, a soft, acidic, warm water setup (pH 6.0–6.8, 79–82 °F) filtered gently through peat or botanicals to mimic blackwater conditions is generally more successful than neutral or alkaline conditions. Fry are tiny at hatching and require infusoria or commercial fry foods before transitioning to newly hatched brine shrimp nauplii.
In the aquarium
Phenacogaster wayana is a specialist's fish rather than a mainstream hobby species; it appears occasionally in imports of mixed Guiana Shield tetras but is not widely available. Its small size — under 2 in — and shoaling temperament make it suited to a biotope aquarium reflecting the clear, tannin-stained forest streams of French Guiana: fine sand or dark substrate, driftwood, dried leaf litter, and gentle filtration with a low flow rate. Soft, slightly acidic water (pH 6.0–7.0, 75–82 °F) suits it well.
As a schooling fish it should be kept in groups of at least eight to ten individuals to express natural behaviour and reduce stress. It is peaceful and compatible with other small Guiana Shield species — pencilfish, small Apistogramma, or fellow Phenacogaster — but should not be housed with anything large enough to eat it. Its translucent body shows to best advantage under a combination of subdued and directed lighting over a dark background.
Conservation
Phenacogaster wayana is assessed as Least Concern (LC) on the IUCN Red List, with the assessment completed on 22 December 2020. The listing reflects the species' presence across multiple river systems in French Guiana and Suriname — a reasonably broad distribution for a small, range-restricted Guiana Shield tetra — and the absence of identified significant conservation threats at the time of assessment.
The Guiana Shield is one of the better-preserved tropical biodiversity hotspots in South America, with large areas of intact forest and relatively limited large-scale agricultural or industrial development compared with other Neotropical regions. That said, gold mining (both legal and artisanal) is an ongoing threat to river water quality in French Guiana and Suriname, contributing sedimentation and mercury contamination to drainages within the species' range. Long-term monitoring of Phenacogaster populations in impacted rivers would strengthen future assessments.