Pimelodidae has a high number of species, but cytogenetic studies are generally restricted to classical chromosomal characterization and in situ localization of ribosomal DNA (rDNA) genes. This study was developed to compare Pimelodus microstoma and Pimelodus pohli focusing on chromosomal diversification provided by the transposition of DNA sequences containing multigene families. Both species share 56 chromosomes, with centromeric and terminal heterochromatic blocks. The silver nucleolus organizer regions (Ag-NORs)/45S rDNA was located in the chromosome pair 24 for both species. The 5S rDNA sites were evidenced in the pair 8 of P. microstoma, and in the pairs 1, 17, and 18 in P. pohli. The U1 small nuclear RNA (snRNA) was located at terminal site in the first subtelocentric pair in both species. The U2 snRNA site was syntenic to 5S rDNA in non-homeologue chromosomes between analyzed species. The histones H3 and H4 were clustered in chromosome pairs 19 and 23 in P. microstoma, and 21 and 22 in P. pohli. Our study proposes that the movement of DNA sequences carrying multigene families has been driven on the chromosomal diversification of Pimelodidae. These multigene location in the genomes can explain most of the visualized chromosomal rearrangements in Pimelodidae and it is useful to understand the chromosomal changes and their distinctive karyotype formulae.

中文翻译：

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两种食蟹猴（Siluriformes：Pimelodidae）的染色体多样性：多基因家族的比较细胞遗传学定位。

mel科具有许多种，但是细胞遗传学研究通常局限于经典的染色体鉴定和核糖体DNA（rDNA）基因的原位定位。开展这项研究的目的是比较Pimelodus microstoma和Pimelodus pohli，后者着重于通过包含多基因家族的DNA序列的转座提供的染色体多样化。这两个物种共有56条染色体，带有着丝粒和末端异色块。银核仁组织者区域（Ag-NORs）/ 45S rDNA位于两个物种的染色体对24中。在微小假单胞菌的第8对中证实了5S rDNA位点，以及P. pohli中的对1、17和18 。的U1小核RNA（snRNA启动）被定位在在这两个物种的第一丝粒对终端站点。在U2 snRNA的网站是同线，以5S rDNA序列的分析物种之间的非homeologue染色体。的组蛋白H3和H4在染色体对19和23被聚P. microstoma，和21和22中P. pohli。我们的研究表明，携带多基因家族的DNA序列的移动已被带到了mel科的染色体多样化中。这些在基因组中的多基因位置可以解释皮mel科的大多数可视化的染色体重排，并且有助于了解染色体的变化及其独特的核型公式。