Cytogenetic and morphological diversity in populations of Astyanax fasciatus (Teleostei, Characidae) from Brazilian northeastern river basins

Abstract

In the present work, morphometric and cytogenetic analyses were carried out in populations of the fish Astyanax fasciatus (Characidae) from Contas and Recôncavo Sul River basins (State of Bahia, Brazil), providing new data on the genetic structure of this species along the region. Based on morphologic measurements, we observed that populations from the same hydrographic basin were more similar to each other (Contas and Preto do Costa Rivers), and remarkably divergent from Recôncavo Sul (Mineiro Stream), as indicated by clustering analysis. Cytogenetic data revealed a same diploid number for all populations (2n = 48), but distinct karyotype formulae (8M+24SM+12ST+4A, FN = 92 in Contas River, 8M+24SM+10ST+6A, FN = 90 in Preto do Costa River, and 8M+18SM+16ST+6A, FN = 90 in Mineiro Stream). Ag-NORs were identified at telomeres on a subtelocentric chromosome pair, although multiple ribosomal sites have been detected in some specimens from Contas River. These results show that A. fasciatus populations from northeastern river basins are well differentiated and present peculiar cytogenetic features when compared to populations from other regions. Therefore, the apparent chromosomal plasticity of this species, likely to represent a complex of cryptic forms, is corroborated. Finally, we demonstrated that morphological features can be successfully used to support other sources of genetic information.

Interpopulational comparative cytogenetics analysis among three Astyanax (Characiformes: Incertae Sedis) species of two streams of upper Paraná River basin, Brazil

“…Souza & Moreira-Filho (1995) stated that the number of chromosomes carrying NORs also denotes an important factor for the differentiation among the populations. The presence of multiple NORs with interpopulational variation is common between the species of A. scabripinnis and A. fasciatus (Ferro et al 2001;Medrado et al 2008), as verified by the present study in A. paranae and A. fasciatus, presenting interpopulational differences in the location and in the number of chromosomes that carrying NORs. Variations in the NORs in A. altiparanae also have been observed (Fernandes & Martins-Santos 2004;Ferreira Neto et al 2009); however, in the present study, both populations presented the same pairs marked by the silver nitrate.…”

“…Differences in the karyotypic formula in distinct populations have been observed in the studies of A. scabripinnis (Alves & Martins-Santos 2002), A. fasciatus (Domingues et al 2007) and A. altiparanae (Medrado et al 2008). The presence of 48 chromosomes in Astyanax scabripinnis complex was also verified in the streams of the up- Malacrida et al 2003).…”

Chromosomal Mapping of Repetitive DNA and Cytochrome C Oxidase I Sequence Analysis Reveal Differentiation among Sympatric Samples of <b><i>Astyanax</i></b><b><i>fasciatus</i></b> (Characiformes, Characidae)

“…fasciatus has already been well characterized, studies concerning chromosomal characteristics together with morphological and/or molecular data are still scarce [Artoni et al, 2006;Pazza et al, 2007Pazza et al, , 2008Medrado et al, 2008;Kavalco et al, 2011]. Therefore, the use of multiple approaches for a better comprehension of evolution in A .…”

Performance of human immunostimulating agents in the improvement of fish cytogenetic preparations

“…This approach has been routinely tested on an array of fish species from several orders such as Perciformes (Sena and Molina, 2007), Anguilliformes (Vasconcelos and Molina, 2009), Beryciformes (Bacurau and Molina, 2004), and Characiformes (Medrado et al, 2008;Pamponet et al, 2008), among others.…”