Physical mapping of the 18S and 5S ribosomal genes in nine Characidae species (Teleostei, Characiformes)

Abstract

Characidae is one of the largest fish families of the Neotropical region, and presenting a pronounced morphological variability, certainly does not constitute a monophyletic group. The cytogenetical data also show a large chromosomal variation and can provide important information for a better understanding of the relationships between the species of this group. 18S and 5S rDNA probes were used in the present study for the chromosomal mapping in different Characidae species from the São Francisco River (Astyanax lacustris, Astyanax scabripinnis, Hasemania nana, Piabina argentea, Orthospinus franciscensis, Serrapinnus heterodon, Serrapinnus piaba and Myleus micans) and Alto Paraná (Astyanax altiparanae) basins. Species with a single pair of chromosomes bearing the nucleolar organizing regions (NORs) were identified, as well as species with multiple NORs, up to a maximum of seven 18S rDNA sites. The number of 5S rDNA site was also not constant, varying from two to eight. The mapping of the ribosomal genes was useful for the characterization and differentiation of the analyzed species.

Cytogenetic and molecular markers reveal the complexity of the genus Piabina Reinhardt, 1867 (Characiformes: Characidae)

“…The 5S rDNA clusters have been identified in two pairs of chromosomes of P. argentea by Peres et al (2008), and this finding is consistent with the data obtained for the P. argentea sample from Itatinga (Fig. 3b).…”

“…Multiple sites of 18S rDNA were found in the sample of P. argentea collected in the São Francisco River Basin and analyzed by Peres et al (2008). Similar sites were also found in the population of P. argentea from the Bauru sample analyzed in the present work (Fig.…”

“…The same chromosome number was observed by Portela et al (1988) and Peres et al (2007Peres et al ( , 2008 in their analysis of P. argentea, which suggests that there is a conserved diploid number for this genus. The same chromosome number is also observed in other fish species belonging to the subfamily Stevardiinae (Oliveira et al, 2005), which includes the genus Bryconamericus (Eigenmann, 1907) and Mimagoniates (Regan, 1907).…”

Cytogenetic data on Astyanax jacuhiensis (Characidae) in the lago Guaíba and tributaries, Brazil

“…data), and in A. altiparanae from the Paraná River (Fernandes & Martins-Santos, 2004) and Monjolinho River (Peres et al, 2008).…”

Allopatric chromosomal variation in Nematocharax venustus Weitzman, Menezes & Britski, 1986 (Actinopterygii: Characiformes) based on mapping of repetitive sequences

“…The remarkable variation of both position and number of ribosomal sites in characins and other Characiformes might reflect the polyphyletism of this fish group (Peres et al, 2008) and/or the association of rDNA with transposable elements (TE) that mobilize adjacent ribosomal sequences (Cioffi et al, 2010). Reinforcing the polymorphic nature of rRNA genes in Characidae, the mapping of 18S and 5S rDNA by FISH revealed clear interpopulation cytogenetic divergence in N. venustus.…”