Despite conservation of the diploid number, a huge diversity in karyotype formulae is found in the Ancistrini tribe (Loricariidae, Hypostominae). However, the lack of cytogenetic data for many groups impairs a comprehensive understanding of the chromosomal relationships and the impact of chromosomal changes on their evolutionary history. Here, we present for the first time the karyotype of Panaqolus tankei Cramer amp; Sousa, 2016. We focused on the chromosomal characterization, using conventional and molecular cytogenetic techniques to unravel the evolutionary trends of this tribe. P. tankei, as most species of its sister group Pterygoplichthini, also possessess a conserved diploid number of 52 chromosomes. We observed heterochromatin regions in the centromeres of many chromosomes; pairs 5 and 6 presented interstitial heterochromatin regions, whereas pairs 23 and 24 showed extensive heterochromatin regions in their q arms. In situ localization of 18S rDNA showed hybridization signals correlating with the nucleolus organizer regions, which are located in the q arms of pair 5. However, the 5S rDNA was detected in the centromeric and terminal regions of the q arms of pair 8. (TTAGGG)_n hybridized only in the terminal regions of all chromosomes. Microsatellite in situ localization showed divergent patterns, (GA)₁₅ repeated sequences were restricted to the terminal regions of some chromosomes, whereas (AC)₁₅ and (GT)₁₅ showed a scattered hybridization pattern throughout the genome. Intraspecific comparative genomic hybridization was performed on the chromosomes of P. tankei to verify the existence of sex-specific regions. The results revealed only a limited number of overlapping hybridization signals, coinciding with the heterochromatin in centromeric regions without any sex-specific signals in both males and females. Our study provides a karyotype description of P. tankei, highlighting extensive differences in the karyotype formula, the heterochromatin regions, and sites of 5S and 18S rDNA, as compared with data available for the genus.
Cytogenet Genome Res

中文翻译：

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Panaqolus tankei Cramer & Sousa, 2016 (Siluriformes, Loricariidae) 的细胞遗传学分析，巴西新谷河特有的观赏鱼

尽管保留了二倍体数量，但在 Ancistrini 部落（Loricariidae，Hypostominae）中发现了核型公式的巨大多样性。然而，由于许多群体缺乏细胞遗传学数据，因此无法全面了解染色体关系以及染色体变化对其进化历史的影响。在这里，我们首次展示了Panaqolus tankei Cramer amp的核型；苏萨，2016 年。我们专注于染色体表征，使用传统和分子细胞遗传学技术来揭示这个部落的进化趋势。油菜与其姐妹群 Pterygoplichthini 的大多数物种一样，也拥有 52 条染色体的保守二倍体数。我们在许多染色体的着丝粒中观察到异染色质区域；对 5 和 6 呈现间质异染色质区域，而对 23 和 24 在其 q 臂中显示广泛的异染色质区域。18S rDNA 的原位定位显示与位于第 5 对 q 臂中的核仁组织者区域相关的杂交信号。然而，在第 8 对 q 臂的着丝粒和末端区域检测到 5S rDNA。（TTAGGG ) _n只在所有染色体的末端区域杂交。微卫星原位定位显示出不同的模式，(GA) ₁₅重复序列仅限于某些染色体的末端区域，而 (AC) ₁₅和 (GT) ₁₅在整个基因组中显示出分散的杂交模式。对P. tankei的染色体进行种内比较基因组杂交以验证性别特异性区域的存在。结果显示只有有限数量的重叠杂交信号，与着丝粒区域的异染色质一致，在雄性和雌性中都没有任何性别特异性信号。我们的研究提供了P. tankei的核型描述，与该属的可用数据相比，突出了核型公式、异染色质区域以及 5S 和 18S rDNA 位点的广泛差异。
细胞遗传基因组研究