Taxonomy & naming
Astyanax gandhiae was formally described in 2018 by Ruiz-C., Román-Valencia, Taphorn, Buckup, and Ortega in the European Journal of Taxonomy. The type series was collected from the upper Cenepa River drainage in the Department of Amazonas, Condorcanqui Province, Peru — a tributary of the Marañón River within the greater Amazon basin. The holotype (MUSM 46845) measures 3.5 in standard length. Additional material was collected from the Ucayali, Loreto, and Puno departments of Peru, indicating a range spanning several major drainages in the Peruvian Amazon.
The species belongs to the orthodus species-group within Astyanax, a vast, species-rich genus in the family Characidae that ranges across much of Latin America. Within the group, A. gandhiae is separated from relatives by a combination of characters: the lateral stripe is short and does not reach anterior to the anal fin origin; no caudal peduncle spot is present; and the maxillary teeth are fewer in number, covering no more than a third of the jaw length. The valid name as governed by the Catalog of Fishes is Astyanax gandhiae Ruiz-C., Román-Valencia, Taphorn, Buckup & Ortega, 2018.
Morphology
Astyanax gandhiae reaches a maximum recorded standard length of 4.5 in, based on the FishBase summary for the species, though the holotype was collected at 3.5 in SL. The body is laterally compressed, with a terminal mouth and a straight dorsal profile between the snout and the supraoccipital spine — a typical bauplan for the orthodus group.
Dentition is characteristic of the group: the premaxillary teeth are arranged in two series, with four tricuspid teeth in the outer row and five pentacuspid teeth in the inner row. The maxilla bears three to six tricuspid teeth. The key diagnostic characters that set this species apart are the short, truncated lateral stripe — confined to the posterior portion of the body and not extending forward past the anal fin origin — the complete absence of a caudal peduncle spot, and the relatively sparse maxillary dentition that does not cover more than a third of the maxillary length. Live colouration data are not documented in published accounts to date.
Habitat
The type locality of Astyanax gandhiae is in the upper Cenepa River drainage in Amazonas Department, northern Peru, at approximately 3°58′15″S, 78°41′15″W, within the Marañón River basin. Additional specimens are known from the Ucayali, Loreto, and Puno departments, suggesting the species is associated with a range of tributaries and drainages across the Peruvian Amazon, from the northern cordilleran foothills to the southern altiplano borderlands.
FishBase classifies the species as freshwater, benthopelagic, and tropical. No fine-scale habitat data — substrate type, current speed, vegetation cover, or riparian structure — are available for this species in the published literature. Given the genus and the Amazonian setting, the fish almost certainly inhabits warm, soft, mildly acidic to near-neutral waters typical of lowland and piedmont Amazonian streams, but specific water chemistry parameters have not been published for A. gandhiae itself.
Feeding
No published dietary data exist for Astyanax gandhiae specifically. Members of the orthodus group and of Astyanax broadly are omnivorous, consuming invertebrates, small fish, algae, and plant material in proportion to availability. The terminal mouth position is consistent with feeding across multiple water column levels.
In the absence of species-specific information, the feeding biology of A. gandhiae should be treated as data sparse. Aquarists who encounter the species would be expected to find it accepting the range of foods typical for Amazonian tetras — small live and frozen invertebrates, quality prepared foods, and some plant matter — but these assumptions are not yet supported by field observations.
Mating
No observations of reproductive behaviour have been published for Astyanax gandhiae. As a characid in the Astyanax lineage, it is expected to follow the egg-scattering pattern typical of the family: sexually active pairs scatter small adhesive eggs among fine-leaved vegetation or other substrate, with no pair bond and no parental care thereafter.
Sexual dimorphism, if present, has not been formally documented for this species. In many Astyanax species, females are stouter-bodied when gravid, but this has not been confirmed for A. gandhiae. The species has a high resilience rating on FishBase, with an estimated population doubling time of less than 15 months, which is consistent with the rapid, prolific spawning characteristic of small characids.
Breeding
Breeding in captivity has not been reported in the available literature for Astyanax gandhiae. On the basis of family-level biology, eggs would be expected to be small and adhesive, scattered among fine-leaved plants or deposited over substrate, hatching within a few days at tropical water temperatures. Adults in Astyanax offer no parental care and will consume both eggs and newly hatched fry, requiring separation if captive propagation is attempted.
Because this species was only described in 2018 and has not entered the aquarium trade as a recognised species, no captive husbandry or breeding accounts are available. Any breeding observations would constitute novel, publishable information.
In the aquarium
Astyanax gandhiae has not been established in the ornamental fish trade as of the description date and is not available commercially under this name. The species is currently known only from museum specimens collected during ichthyological surveys in Peru. Accordingly, there are no aquarium care accounts, and caregiving recommendations cannot be made on a species-specific basis.
Aquarists who might encounter this fish — for example, as an incidental catch in mixed lots of Peruvian wild-caught tetras — should treat it as a standard small Astyanax: a sociable, active schooling fish suited to a planted aquarium with soft to moderately hard, slightly acidic to neutral warm water, housed with similarly sized peaceful companions. Its maximum recorded size of 4.5 in SL means it is a medium-sized tetra by genus standards, requiring a tank of adequate length.
Conservation
Astyanax gandhiae has not been formally assessed by the IUCN Red List and carries no conservation status. FishBase records the species as Not Evaluated. Because it was described only in 2018, the population size, degree of endemism, and any pressures on its habitat across its Peruvian range have not been quantified in the conservation literature.
The species is documented from several departments of Peru — Amazonas, Ucayali, Loreto, and Puno — which, if confirmed, suggests a distribution broad enough to reduce immediate extinction risk relative to a narrow endemic. However, Amazonian stream fish communities throughout this region face ongoing pressure from deforestation, agricultural runoff, and small-scale mining activities. A formal IUCN assessment would be needed to evaluate whether A. gandhiae warrants a threat category.