Taxonomy & naming
Aphyolebias claudiae was described by Jean H. Huber in 1998 and is placed within the family Rivulidae, subfamily Rivulinae — the South American rivulines, a large and taxonomically intricate radiation of annual and non-annual killifishes spanning the continent's seasonal lowlands. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) records the valid combination as Aphyolebias claudiae (Huber, 1998); the parenthetical authority indicates the species has been moved from the genus in which it was originally placed.
The genus Aphyolebias is a small Andean-foothill and adjacent lowland genus within the rivuline tribe, characterised by annual life histories tied to the flooding rhythms of the Mamoré and Guaporé sub-basins of Bolivia and adjacent Peru. Aphyolebias claudiae is regarded as one of the more distinctively marked members of the genus, and its rediscovery in 2024 — reported by Drawert and Litz in the journal Nature Conservation — prompted renewed attention to the taxonomic and conservation standing of this species.
Morphology
Males of Aphyolebias claudiae reach a maximum of 1.5 in standard length; females are smaller, reaching up to 1.5 in SL (Drawert & Litz 2025). The species exhibits the marked sexual dichromatism typical of the genus: males are brightly coloured, the distinguishing feature that made them recognisable to killifish hobbyists and prompted the rediscovery effort; females are cryptically coloured in the brown and olive tones common to rivuline females.
The body form is typical of the South American annual rivulines — a moderately elongate, laterally compressed profile with a relatively large mouth suited to ambush predation on invertebrates. The exact colour pattern description from the original 1998 description is not fully reproduced here, but the vivid male colouration is a consistent feature noted in hobby literature and was the basis on which the rediscovered population was identified as A. claudiae by killifish specialists in the field.
Habitat
The type locality of Aphyolebias claudiae lies at approximately 15°37'S, 63°35'W on the floodplains of the Río San Pablo, roughly 37 mi north of Ascención de Guarayos in the Iténez (Guaporé) basin of lowland Bolivia. Field survey in 2024 confirmed this original site has been destroyed by deforestation and agricultural conversion. The rediscovered population occupies a seasonal blackwater pool at approximately 15°04'S, 64°20'W, within the Mocovi River drainage of the Ibare River basin — itself a sub-basin of the Mamoré — some 62 mi northwest of the type locality.
The rediscovered habitat is a temporary flooded forest pool with a dense leaf-litter substrate, a maximum recorded depth of only 1 ft, and no submerged vegetation. Water chemistry reflects the blackwater character of the Bolivian lowland forest: stained, soft, and acidic. The pool dries out completely during the dry season; A. claudiae survives the drought as buried eggs in diapause. Six other rivulid species were recorded syntopically at the rediscovered site, confirming the habitat's importance for the broader annual killifish community of this drainage.
Feeding
No detailed dietary study specific to Aphyolebias claudiae has been published; however, the feeding biology of the species can be inferred from closely related South American annual rivulines. Members of Aphyolebias and allied genera are generalised micropredators, consuming small aquatic invertebrates — insect larvae (chironomids, mosquito larvae), microcrustaceans, worms, and similar soft-bodied prey — that proliferate in the newly flooded seasonal pools the fish inhabit.
In captivity, A. claudiae and related Aphyolebias species are reported to take live foods readily: brine shrimp nauplii and adults, Daphnia, small tubifex, and bloodworm. A diet weighted toward live or frozen invertebrates is recommended to maintain the intense colouration of males and to support the high metabolic rate associated with the species' compressed annual life cycle.
Mating
Aphyolebias claudiae is an annual killifish that reproduces by substrate-spawning — pairs dive into and bury eggs within the soft peat, mud, and detritus of the pool floor. This is the defining reproductive strategy of the South American annual killifish radiation: rather than depositing eggs on plants or other surfaces where they would desiccate as the pool dries, the eggs are placed deep in the substrate where moisture is retained through the dry season.
Male Aphyolebias are colourful and likely perform visual courtship displays toward females. Competition between males is presumed to be intense given the short season available for reproduction; males typically mature quickly and invest heavily in courtship and spawning activity during the brief wet-season window. In aquarium conditions, pairs are usually housed together in a small, peat-floored tank — the standard approach for annual killifish — to facilitate natural substrate-spawning behaviour.
Breeding
Like all South American annual killifishes, Aphyolebias claudiae deposits eggs in the substrate that then enter diapause — a state of arrested embryonic development that allows the eggs to survive the complete desiccation of their natal pool through the Bolivian dry season. When the rains return and the pool refills, the eggs resume development and hatch, producing a new generation that must grow, mature, spawn, and bury their own eggs before the pool dries again — completing the entire life cycle within a single wet season.
In the aquarium, the standard protocol for annual killifish applies: pairs are placed in a small tank with a layer of peat or coconut coir as the spawning substrate. After several weeks of spawning, the peat is removed, gently squeezed to remove excess water, and stored in a sealed bag or container at a moderate temperature for a diapause period of several weeks to months. The peat is then re-wetted to trigger hatching. First foods for the fry are infusoria and freshly hatched brine shrimp nauplii; growth is rapid in warm water, consistent with the selective pressure to reach reproductive maturity before the season ends. British Killifish Association records confirm the peat-spawning protocol for this genus, noting 2.3-gallon peat-substrate tanks as appropriate for Aphyolebias spawning setups.
In the aquarium
Aphyolebias claudiae has appeared in killifish hobby circles and is recorded in the Killi-News archives of the British Killifish Association, confirming its presence in specialised collections. As with most annual killifishes from Bolivia and adjacent lowlands, it requires the dedicated care approach used for peat-spawners: a small, species tank or a pair or trio setup, a soft peat or coir substrate, and water conditions that reflect the soft, slightly acidic blackwater pools of its native habitat.
Temperature should be kept moderate — Bolivian lowland annual killifishes do poorly in the higher temperatures sometimes used for tropical fish; a range of around 72–79 °F is appropriate, with cooler temperatures helping to extend the animals' naturally brief lifespan in captivity. Live and frozen foods are strongly recommended. Because of the species' Critically Endangered status and the destruction of its type locality, captive husbandry takes on added significance: responsible breeding programmes within the killifish hobby can maintain insurance populations and preserve genetic material while wild habitat work is pursued.
Conservation
The IUCN Red List assesses Aphyolebias claudiae as Critically Endangered (CR) under criterion B2ab(iii), with the assessment conducted by Carvajal-Vallejos et al. in 2016. The CR listing reflects the species' extremely limited known range, the destruction of the type locality by deforestation and agricultural expansion, and the ongoing deterioration of its seasonal forest-pool habitat throughout the Bolivian lowlands.
The 2024 rediscovery by Drawert and Litz, published in the journal Nature Conservation, provided a rare piece of encouraging news: a surviving population was located approximately 62 mi northwest of the destroyed type locality, in a seasonal blackwater pool within the Mocovi River drainage of the Ibare–Mamoré system. The survival of this population was unknown at the time of the 2016 IUCN assessment, which had been based on the apparent destruction of the only known locality. The rediscovered site remains vulnerable: the drivers of habitat loss across Bolivia's lowland Amazonian fringe — agricultural conversion, cattle pasture expansion, road building, and drainage of seasonal wetlands — have not abated.
The species illustrates the acute conservation problem facing narrow-range annual killifishes globally: their entire existence depends on the persistence of temporary pools that are trivially easy to drain, fill, or convert. A single plough cutting through the wrong wet-season forest patch can eliminate a species' only population. The killifish hobbyist community, through species preservation programmes coordinated by organisations such as the British Killifish Association and the American Killifish Association, represents one of the few practical mechanisms for maintaining captive assurance populations of species like A. claudiae while longer-term wild habitat protection is pursued.