Taxonomy & naming
Anablepsoides gaucheri was described by Keith, Le Bail and Planquette in 2000, in the comprehensive survey 'Poissons d'eau douce de Guyane' — the authoritative reference work covering the freshwater fishes of French Guiana. The original description placed the fish in the genus Rivulus, which historically served as the receptacle for virtually all New World rivuline killifishes. Subsequent molecular and morphological revision of that assemblage resulted in the genus Rivulus being dismembered into a set of more natural, monophyletic genera; the valid combination is now Anablepsoides gaucheri (Keith, Le Bail & Planquette, 2000) under the genus Anablepsoides Costa, 2011, which accommodates the larger-bodied, elongate South American rivulines. The parentheses around the authority signal that the original generic assignment has been changed.
The specific epithet gaucheri is a Latinised genitive, most probably a patronym honouring an individual named Gaucher who contributed to the original collecting or study of the material — a common practice in Guianan ichthyology, where many species are named for local biologists, naturalists, or collectors. The Catalog of Fishes (Eschmeyer, Fricke and van der Laan) records the valid name as Anablepsoides gaucheri (Keith, Le Bail & Planquette, 2000) and that combination is followed here. No synonyms are listed for this species in the sources available.
Morphology
Specific morphological data for Anablepsoides gaucheri is sparse in the sources reviewed. As a member of the genus Anablepsoides the species can be expected to share the group's general body plan: a slender, slightly cylindrical to gently laterally compressed form, a subtly upturned mouth oriented toward the water surface, and dorsally placed eyes that give the fish a wide field of view above the water — morphological features linked to the surface- and near-surface foraging strategy characteristic of this group.
Males across Anablepsoides typically display brighter colouration than females, with rows of reddish or brownish spots or vermiculations on the flanks and often with extended, pigmented dorsal and caudal fins in breeding condition. Females are generally plainer and develop a notably rounded abdomen when gravid. Species-specific size and colouration data for A. gaucheri is not documented in the sources available; the typical size range for Anablepsoides species from the Guianas falls roughly between 4 and 3 in total length.
Habitat
French Guiana is the sole documented range for Anablepsoides gaucheri. The country's freshwater fish fauna drains into the Atlantic via a series of coastal rivers — among them the Maroni (which forms the border with Suriname), the Sinnamary, the Approuague, and the Oyapock (which forms the border with Brazil) — and their associated tributary networks. The interior is largely covered by intact Amazonian-type rainforest underlain by the Guiana Shield, one of the geologically oldest land masses on Earth, and the upland streams are typically clear, soft, and mildly acidic, while coastal-plain waterways can carry more tannin staining from decaying leaf litter.
Anablepsoides species in the Guiana region are non-annual: they are found in permanent or near-permanent watercourses where water persists year-round, rather than in seasonal pools that dry completely during the dry season. This habitat association is the ecological basis for their plant-spawning, non-diapausing reproductive strategy. The species is expected to favour shallow, vegetated margins of forest streams and pools, where submerged plant matter, roots, and leaf litter provide both cover and spawning substrate. Specific water chemistry data for the collecting localities of A. gaucheri is not documented in the sources reviewed; Guianan lowland streams of this type typically run at temperatures of 72–82 °F with pH values broadly in the range of 5.5–7.0 and low hardness.
Feeding
No dietary study specific to Anablepsoides gaucheri has been published in the sources reviewed. Based on the biology of closely related Guianan Anablepsoides species and the group's morphological features — upturned mouth, dorsally positioned eyes, surface-oriented body posture — the wild diet is presumed to consist primarily of small invertebrates: aquatic insect larvae, small worms, crustaceans such as copepods and cladocerans, and terrestrial insects falling onto or near the water surface.
In the aquarium, rivulines of this group are best maintained on a varied diet centred on live and frozen invertebrate prey: brine shrimp (nauplii and adults), daphnia, cyclops, micro-worms, and small chironomid larvae. Acceptance of prepared dry foods varies among individual fish and populations; offering a mix of live, frozen, and high-quality granular food is advisable to ensure complete nutrition and maintain the brighter colouration that breeding males display.
Mating
Anablepsoides gaucheri is a non-annual killifish. The permanent-water habitat of the Guianan forest streams it occupies means there is no seasonal desiccation event driving the evolution of diapausing eggs, and the species instead reproduces by the plant-spawning strategy typical of non-annual South American rivulines. Pairs spawn repeatedly over an extended period, depositing small numbers of adhesive eggs among fine-leaved aquatic vegetation, floating surface roots, or fibrous spawning mops provided in aquarium settings. Each spawning act produces one or a small number of eggs rather than a large clutch, and the process is repeated across days and weeks.
Male Anablepsoides signal breeding readiness through intensified body colouration and erect, fanned unpaired fins. Courtship consists of the male positioning alongside and below the female, displaying laterally, and guiding her toward the spawning site. The pair align side by side at or near the substrate or surface vegetation, and a brief embrace or tight juxtaposition accompanies each egg release. No parental care follows spawning.
Breeding
The eggs of Anablepsoides gaucheri are adhesive and incubate in water at ambient temperature — there is no diapause, no requirement for dry storage in peat or coir, and no need for a wet-then-dry incubation cycle. At temperatures in the range typical for Guianan rivulines (75–81 °F), incubation for non-annual Anablepsoides generally takes two to four weeks; fertility should be checked by candling eggs every few days, with unfertilised or fungused eggs removed promptly to prevent spread.
Aquarists working with Guianan non-annual rivulines typically remove egg-bearing plants or mop strands to a separate shallow rearing vessel with gentle aeration and aged water matched to the parent tank's parameters. Fry are small but capable feeders immediately upon hatching, accepting newly hatched brine shrimp nauplii, micro-worms, and commercial fry foods as first foods. Water quality in the rearing vessel must be maintained carefully; small daily partial water changes with temperature-matched water prevent ammonia and nitrite accumulation that would otherwise suppress growth or cause losses. Growth proceeds steadily and sexual maturity is typically reached within several months.
In the aquarium
Anablepsoides gaucheri is essentially absent from the mainstream aquarium hobby and is not listed by major hobbyist databases. Guianan Anablepsoides species as a group occupy a niche corner of the killifish hobby, appealing primarily to killifish specialists and members of organisations such as the American Killifish Association or the Deutsche Killifisch Gemeinschaft, where occasional imports or captive-bred material circulates through study-group auctions and species distribution lists.
For those who do obtain this fish, the appropriate setup mirrors that used for other small, non-annual rivulines from the Guianas: a modestly sized, well-covered species aquarium of 5.5–10 US gal with gentle filtration, a dark substrate and background, floating surface cover (Indian fern, water lettuce, or floating mop material), and stable water conditions in the temperature range of approximately 72–81 °F with moderately soft, slightly acidic to neutral water. A tight-fitting lid is essential — rivulines jump readily and can escape through surprisingly small gaps. Tankmates, if used at all, should be small and non-competitive; housing a pair or small group as a species-only setup is the preferred approach for breeding efforts. Willingness to invest in live and frozen food provision and meticulous water quality management is a prerequisite for success.
Conservation
Anablepsoides gaucheri has not been formally assessed by the IUCN Red List; it carries a status of Not Evaluated (NE). For a species endemic to a single country — French Guiana — with an apparently restricted distribution in the coastal-plain and forest-stream systems of the Guiana Shield, the absence of an assessment does not indicate ecological security. Several Anablepsoides species from similarly restricted Guianan habitats are known to have very small areas of occupancy, and species described from a single or small number of collecting localities are inherently vulnerable to localised habitat degradation.
French Guiana's forest cover remains comparatively intact relative to other parts of the Guianan Shield, and the country's status as a French overseas territory affords some regulatory protection to its interior. However, coastal-plain habitats — the lowland streams and swampy margins most likely to support this species — face mounting pressure from urban expansion around Cayenne and associated infrastructure development, agricultural drainage, and modification of watercourses for road building. Gold mining in the interior, which affects stream water quality through mercury contamination and sedimentation, is an additional threat to Guianan freshwater biodiversity. A targeted survey to characterise the range, population size, and habitat requirements of A. gaucheri, followed by a formal IUCN assessment, would be a meaningful step toward understanding the conservation status of this and related underevaluated Guianan rivulines.