Untitled

Abstract

Astyanax scabripinnis has been considered a species complex because it presents high karyotypic and morphological variability among its populations. In this work, individuals of two A. scabripinnis populations from different streams in the same hydrographic basin were analyzed through C-banding and AgNOR. Although they present distinct diploid numbers, they show meta and submetacentric chromosome groups highly conserved (numerically and morphologically). Other chromosomal characteristics are also shared by both populations, as the pattern of constitutive heterochromatin distribution (large blocks in the telomeric regions of subtelocentric and acrocentric chromosomes) and some nucleolar chromosomes. Inter-individual variations both in the number and size of heterochromatic blocks, and in the number and localization of NORs were verified in the studied populations, characterizing them as polymorphics for these regions. The mechanisms involved in the dispersion of heterochromatin and NORs through the karyotypes, as well as the possible events related to the generation of polymorphism of those regions are discussed. Furthermore, relationships between these populations and within the context of the scabripinnis complex are also approached.

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

“…Although there are different patterns of heterochromatin in A. scabripinis and A. fasciatus, the pattern of centromeric heterochromatin verified here in A. paranae was also observed by some authors in A. scabripinnis (Stange & Almeida-Toledo 1993; Souza et al 1996;Mantovani et al 2000;Vicari et al 2008). In A. fasciatus, the presence of telomeric heterochromatin verified in the present study was also observed by other authors (Daniel-Silva & Almeida Toledo 2001;Centofante et al 2003;Pazza et al 2008).…”

Karyotypic conservatism in five species of Prochilodus (Characiformes, Prochilodontidae) disclosed by cytogenetic markers

“…Differences in the amount or distribution of heterochromatin identified by C-banding are considered important for some fish groups and the distribution of C-bands may characterize genera, species and populations (Montovani et al , 2000). …”

Comparative cytogenetics among populations of Astyanax altiparanae (Characiformes, Characidae, Incertae sedis)

“…In the Jordão River population, chromosome pair 2 was smaller than the same pair in the Pântano and Feijão Streams populations (Figure 1). Variations in diploid number were observed between populations of species from the A. scabripinnis and A. fasciatus complexes and resulted from chromosome translocations (Mantovani et al , 2000; Artoni et al , 2006; Vicari et al , 2008a). Nevertheless, A. altiparanae exhibited a conserved 2n = 50 chromosomes in all the populations karyotyped (Table 1).…”