Distribution and morphological diversity of Astyanax rivularis Lütken, 1874 (Teleostei Characiformes) in the upper São Francisco River basin, Brazil

Abstract

Baird et Girard, 1854 (Teleostei Characiformes) is one of the most well characterized of the neotropical ichthyofauna and is composed of fish with great ability to adapt to different environmental conditions and a wide spectrum of interaction in fish assemblages due to its structure and population density. This study presents the geographical distribution and morphological diversity of Astyanax rivularis Lütken, 1874, a fish historically complex and extremely diverse, in tributary streams of the left side of upper São Francisco River.

Gonadal morphology and difference in reproductive development of two isolated populations of Astyanax rivularis (Teleostei, Characidae)

“…Data on the morphological diversity of populations of A. rivularis have been previously described and seven distinct populations distributed throughout the São Francisco River Basin have been established, demonstrating variety of size, shape and even meristic count for this species (Pasa et al, 2019). As a behavioural characteristic, animals of this genus present difficulty to pass through geographical barriers and tend to isolate themselves in different populations (Shibatta et al, 2002).…”

“…Among the species of this genus, Astyanax rivularis is an endemic species of the São Francisco River basin (Fricke et al, 2019). This basin crosses the Serra da Canastra, a mountain range considered a biodiversity hotspot and located in the southern centre of the state of Minas Gerais, Brazil (Pasa et al, 2019;Souza et al, 2014). A. rivularis specimens are small, omnivorous and diurnal animals that actively swim in the water column (Casatti & Castro, 1998;Casatti & Castro, 2006).…”

Ecomorphology of yellowtail lambari (Characiformes: Characidae) in the neotropical semi-arid region, Brazil

“…Among the smallsized species, the genus Astyanax Baird & Girard (1854), belonging to the family Characidae, order Characiformes, is one of the most diverse, with about 128 valid species (Toledo-Piza et al, 2024) and an increase of about 40 new species in the last ten years (Salgado, 2021). This genus is composed of fish with a remarkable ability to adapt to different environmental conditions and a wide distribution from the south of the United States of America to the north of Argentina (Garita-Alvarado and Ornelas-García, 2021;Pasa et al, 2019).…”