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Abstract：
BACKGROUND: Chromosomal painting in manatees has clarified questions about the rapid evolution of sirenians within the Paenungulata clade. Further cytogenetic studies in Afrotherian species may provide information about their evolutionary dynamics, revealing important insights into the ancestral karyotype in the clade representatives. The karyotype of Trichechus inunguis (TIN, Amazonian manatee) was investigated by chromosome painting, using probes from Trichechus manatus latirostris (TML, Florida manatee) to analyze the homeologies between these sirenians.
RESULTS: A high similarity was found between these species, with 31 homologous segments in TIN, nineteen of which are whole autosomes, besides the X and Y sex chromosomes. Four chromosomes from TML (4, 6, 8, and 9) resulted in two hybridization signals, totaling eight acrocentrics in the TIN karyotype. This study confirmed in TIN the chromosomal associations of Homo sapiens (HSA) shared in Afrotheria, such as the 5/21 synteny, and in the Paenungulata clade with the syntenies HSA 2/3, 8/22, and 18/19, in addition to the absence of HSA 4/8 common in eutherian ancestral karyotype (EAK).
CONCLUSIONS: TIN shares more conserved chromosomal signals with the Paenungulata Ancestral Karyotype (APK, 2n = 58) than Procavia capensis (Hyracoidea), Loxodonta africana (Proboscidea) and TML (Sirenia), where TML presents less conserved signals with APK, demonstrating that its karyotype is the most derived among the representatives of Paenungulata. The chromosomal changes that evolved from APK to the T. manatus and T. inunguis karyotypes (7 and 4 changes, respectively) are more substantial within the Trichechus genus compared to other paenungulates. Among these species, T. inunguis presents conserved traits of APK in the American manatee genus. Consequently, the karyotype of T. manatus is more derived than that of T. inunguis.
RESULTS: A high similarity was found between these species, with 31 homologous segments in TIN, nineteen of which are whole autosomes, besides the X and Y sex chromosomes. Four chromosomes from TML (4, 6, 8, and 9) resulted in two hybridization signals, totaling eight acrocentrics in the TIN karyotype. This study confirmed in TIN the chromosomal associations of Homo sapiens (HSA) shared in Afrotheria, such as the 5/21 synteny, and in the Paenungulata clade with the syntenies HSA 2/3, 8/22, and 18/19, in addition to the absence of HSA 4/8 common in eutherian ancestral karyotype (EAK).
CONCLUSIONS: TIN shares more conserved chromosomal signals with the Paenungulata Ancestral Karyotype (APK, 2n = 58) than Procavia capensis (Hyracoidea), Loxodonta africana (Proboscidea) and TML (Sirenia), where TML presents less conserved signals with APK, demonstrating that its karyotype is the most derived among the representatives of Paenungulata. The chromosomal changes that evolved from APK to the T. manatus and T. inunguis karyotypes (7 and 4 changes, respectively) are more substantial within the Trichechus genus compared to other paenungulates. Among these species, T. inunguis presents conserved traits of APK in the American manatee genus. Consequently, the karyotype of T. manatus is more derived than that of T. inunguis.
摘要：
背景：海牛的染色体绘画已经澄清了有关Paenungulata进化枝中的鼠尾草快速进化的问题。对非洲物种的进一步细胞遗传学研究可能会提供有关其进化动力学的信息，揭示了进化枝代表祖先核型的重要见解。inunguis（TIN，亚马逊海牛）通过染色体绘画进行了研究，使用来自Trichusmanatuslatirostris（TML，佛罗里达海牛）来分析这些海牛之间的同源性。
结果：在这些物种之间发现了很高的相似性，在TIN中有31个同源片段，其中19个是完整的常染色体，除了X和Y性染色体.来自TML的四个染色体(4、6、8和9)产生两个杂交信号,TIN核型中总共有8个acrocentric。这项研究在TIN中证实了南非人（HSA）的染色体关联，例如5/21同理，以及在具有同构HSA2/3、8/22和18/19的Paenungulata进化枝中，除了在Eutherian祖先核型（EAK）中不存在HSA4/8。
结论：TIN与Paenungulata祖先核型共享更保守的染色体信号（APK，2n=58)比Procaviacapensis(Hyracoidea)，非洲Loxodonta（Proboscidea）和TML（Sirenia），其中TML与APK呈现较少保守的信号，证明其核型是Paenungulata代表中最衍生的。从APK演变为T.manatus和T.inunguis核型的染色体变化（7和4变化，分别）与其他paenumulates相比，在毛虫属中的含量更高。在这些物种中,T.inunguis表现出美国海牛属中APK的保守特征。因此,Manatus的核型比Inunguis的核型更多。
结果：在这些物种之间发现了很高的相似性，在TIN中有31个同源片段，其中19个是完整的常染色体，除了X和Y性染色体.来自TML的四个染色体(4、6、8和9)产生两个杂交信号,TIN核型中总共有8个acrocentric。这项研究在TIN中证实了南非人（HSA）的染色体关联，例如5/21同理，以及在具有同构HSA2/3、8/22和18/19的Paenungulata进化枝中，除了在Eutherian祖先核型（EAK）中不存在HSA4/8。
结论：TIN与Paenungulata祖先核型共享更保守的染色体信号（APK，2n=58)比Procaviacapensis(Hyracoidea)，非洲Loxodonta（Proboscidea）和TML（Sirenia），其中TML与APK呈现较少保守的信号，证明其核型是Paenungulata代表中最衍生的。从APK演变为T.manatus和T.inunguis核型的染色体变化（7和4变化，分别）与其他paenumulates相比，在毛虫属中的含量更高。在这些物种中,T.inunguis表现出美国海牛属中APK的保守特征。因此,Manatus的核型比Inunguis的核型更多。
