Anostomidae species have conserved diploid numbers (2n = 54), although comparative cytogenetic studies have demonstrated chromosomal rearrangements occurrence among them, especially in repetitive DNA rich regions. The location and distribution of ribosomal DNA (rDNA) and small nuclear RNAs (snRNAs) multigene families are highly dynamic in the genomes of several organisms. In this study, we in situ located the rDNA and snRNA sites in two populations of Megaleporinus obtusidens and a sample of Megaleporinus reinhardti to infer their chromosomal changes in the evolutionary lineages. Both species of Megaleporinus shared 2n = 54 chromosomes with the presence of ZZ/ZW sex chromosome system, but they diverged in relationship to the location of 5S and 45S rDNAs as well as the distribution of snRNAs sites. The characterization of the analyzed sequences revealed the presence of complete rDNA and snRNAs sequences as well as snRNAs containing transposable elements (TEs) and microsatellite repeats. After chromosomal mapping, the sequences encompassing TEs proved to be dispersed through autosomes and accumulated on sex chromosomes. The data demonstrate that intra- and interspecific chromosomal changes occurred involving the multigene family's sites in Megaleporinus karyotypes. Furthermore, we detected TE-like sequences in the differentiation of sex chromosome systems in M. obtusidens and M. reinhardti.

中文翻译：

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从重复DNA序列的原位定位推断两个巨噬菌属物种（Characiformes，Anostomidae）的核型多样化。

尽管比较细胞遗传学研究表明，其中有染色体重排发生，特别是在重复的DNA富集区域，但拟南芥属物种的二倍体数目却保守（2n = 54）。核糖体DNA（rDNA）和小核RNA（snRNA）多基因家族的位置和分布在几种生物的基因组中是高度动态的。在这项研究中，我们在现场位于rDNA序列和S nRNA网站在两个群体的Megaleporinus obtusidens和样本Megaleporinus reinhardti推断在进化谱系的染色体变化。巨Mega属的两种在存在ZZ / ZW性染色体系统的情况下共有2n = 54条染色体，但是它们在5S和45S rDNA的位置以及snRNA位点的分布方面存在分歧。所分析的序列的表征揭示完整rDNA和存在snRNAs序列以及snRNAs含有转座元件（TES）和微卫星重复。染色体作图后，证明包含TEs的序列通过常染色体分散并积累在性染色体上。数据表明种内和种间染色体发生了变化，涉及巨耳孢菌属中的多基因家族的位点核型。此外，我们检测到了M. obtusidens和M. reinhardti的性染色体系统分化中的TE样序列。