Chromosome polymorphism in <i>Astyanax fasciatus</i> (Teleostei, Characidae). 2 – Chromosomal location of a satellite DNA

Abstract

Studies about composition of repetitive sequences and their chromosomal location have been helpful to evolutionary studies in many distinct organisms. In order to keep on assessing the possible relationships among different cytotypes of Astyanax fasciatus (Teleostei, Characiformes) in the Mogi-Guaçu River (São Paulo State, Brazil), C-banding, chromomycin A₃ staining, and fluorescent in situ hybridization with a repetitive DNA sequence (As51) isolated from Astyanax scabripinnis were performed in the present work. The constitutive heterochromatin was distributed in terminal regions on long arms of submetacentric, subtelocentric, and acrocentric chromosomes and in the terminal region on short arms of a pair of submetacentric chromosomes in both standard cytotypes. This latter heterochromatic site was also GC-rich, as revealed by chromomycin A₃ staining, corresponding to the nucleolar organizer region (NOR), as shown by previous studies. The sites of the satellite As51 DNA were located in terminal regions on long arms of several chromosomes. Some variant karyotypic forms, which diverge from the two standard cytotypes, also presented distinctive chromosomes carrying As51 satellite DNA. It is possible that the standard 2n = 46 cytotype represents an invader population in the Mogi-Guaçu River able to interbreed with the resident standard 2n = 48 cytotype. Therefore, the variant karyotypes would be related to a possible viable offspring, where complementary chromosomal rearrangements could favor new locations of the satellite DNA analyzed.

Divergence of Repetitive DNA Sequences in the Heterochromatin of Medaka Fishes: Molecular Cytogenetic Characterization of Constitutive Heterochromatin in Two Medaka Species: <b><i>Oryzias hubbsi</i></b> and <b><i>O. celebensis</i></b> (Adrianichthyidae, Beloniformes)

“…The 177-bp OHU-Rsa I-Stelo was also shown to be an AT-rich highly repetitive sequence, which constituted telomeric heterochromatin at the proximal and/or distal ends of about half of all acrocentric chromosomes. Very similar types of AT-rich telomere-specific repetitive sequences have also been reported for Parodon hilarii of the Parodontidae [Vicente et al, 2003] and Astyanax fasciatus of the Characidae [Mestriner et al, 2000;Pazza et al, 2008;Vicari et al, 2008]. These centromeric/telomeric repetitive sequences have evolved in a concerted manner, predominantly via recombination events among homologous chromosome regions.…”

“…chromomycin A3) [Sumner, 1990]. Information on the chromosomal distribution and nucleotide sequences of highly repetitive DNA and their genomic organization has enabled more precise characterization of constitutive heterochromatin in many teleostean fish species [Garrido-Ramos et al, 1994;Oliveira and Wright, 1998;Fischer et al, 2000;Mestriner et al, 2000;Phillips and Reed, 2000;Canapa et al, 2002;de Jesus et al, 2003;Vicente et al, 2003;de la Herrán et al, 2008;Pazza et al, 2008] and the phylogenetic relationships between related fish species [Garrido-Ramos et al, 1995;Mazzuchelli and Martins, 2009].…”

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)

“…These characteristics are related to distinct karyotype macrostructure and diploid number, ranging from 36 to 50 chromosomes [Moreira-Filho and Bertollo, 1991;Almeida-Toledo et al, 2002;Pazza et al, 2008], occurrence of B chromosomes Hashimoto et al, 2011], different patterns of constitutive heterochromatin distribution [Mantovani et al, 2000;Hashimoto and Porto-Foresti, 2010], and differential dispersion of repetitive DNAs [Almeida-Toledo et al, 2002;Kantek et al, 2009]. In A .…”

“…Similarly, cytogenetic studies also reveal an extensive diversity in Astyanax [Morelli et al, 1983;Moreira-Filho and Bertollo, 1991;Almeida-Toledo et al, 2002;Pazza et al, 2008] and may help understanding relationships among different species and populations. Indeed, some species exhibit populations with constant diploid numbers, like A .…”

“…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 .…”