male specimens. Females also tend to be more common than males. Taxonomy When first described, A. abramis was given the basionym Tetragonopterus abramis. English naturalist Leonard Jenyns prescribed this name in 1842, building from the work of well-known English natural historian Charles Darwin, who collected the type specimens in the 19th century. At one point, it was described as a separate species under the name Bertoniolus paraguayensis, but this name has been synonymized with A. abramis. In 2016, its classification as a species was confirmed as valid, and it received a redescription. Within Astyanax, there are three subgenera - Astyanax strictu sensu, Poecilurichthys, and Zygogaster. Multiple species in the genus Astyanax are considered cryptic - that is, two or more possible species that are currently considered synonymous because of remarkable similarity, but that cannot reproduce with each other. A. abramis is no exception to this and is considered a cryptic species. It is also a part of the Astyanax bimaculatus species complex, alongside Astyanax lacustris. At the time of description, Jupiaba species J. abramoides was believed to be closely related to A. abramis. This is the origin of its specific epithet - "oides" means "having the shape of". The basionym of J. abramoides is, in fact, Astyanax abramoides. Etymology and nomenclature The specific name "abramis" is an allusion to European species Abramis brama, a leuciscid that has a similar body shape (described as "subrhomboidal"). The genus name "Astyanax" comes from a figure in Homer's Iliad, Astyanax, who was the son of Hector, a famed Trojan warrior. Why the genus has this name was not made clear in the original text, but could possibly refer to the large, armor-like scales of species A. argentatus. In terms of a common name, A. abramis is one of various species of Astyanax referred to as "lambari". Distribution and habitat Astyanax abramis can be found in the La Plata basin, as well as the upper Amazon and Meta River basins. It is most often found in lentic (still water) environments. Lentic environments, without the oxygenation provided by flowing water, are generally lower in dissolved oxygen, which has resulted in A. abramis developing adaptations to such conditions, including morphological plasticity (albeit limited). The relevant habitat stretches through multiple countries, including Brazil, Argentina, Bolivia, Uruguay, and Paraguay. Specific rivers, regions, and tributaries include the Juramento, Yabotí, and Parana. Ecology and biology In environments of strong hypoxia, A.