Amorim K D J, Cioffi M B, Bertollo L A C, Soares R X, Calado L L, Borges A T, Costa G W W F, Molina W F
Departamento de Biologia Celular e Genética, Centro de Biociências, , , Brasil.
Departamento de Genética e Evolução, , , Brasil.
Genet Mol Res. 2017 May 10;16(2):gmr-16-02-gmr.16029650. doi: 10.4238/gmr16029650.
The distribution patterns of marine biodiversity are complex, resulting from vicariant events and species dispersion, as well as local ecological and adaptive conditions. Furthermore, the wide geographic distribution of some species may be hindered by biogeographical barriers that can interfere in the gene flow. Cytogenetic analyses in marine fishes, especially those involving populations in small remote insular environments, remain scarce. In the Western Atlantic, species of wrasses from the genera Halichoeres and Thalassoma occur in biogeographic arrangements that make it possible to analyze cytogenetic patterns between coastal and widely separated island populations. Species of these genera were punctually analyzed in some Atlantic regions. In this study, we compared several chromosomal features, such as karyotype macrostructure, heterochromatic patterns, patterns of base-specific fluorochromes, Ag-NORs, and 18S and 5S ribosomal sites in Thalassoma noronhanum, Halichoeres poeyi, and Halichoeres radiatus individuals from distinct coastal or insular regions of Atlantic. Notably, all of them are characterized by multiple 18S and 5S rDNA sites with syntenic arrangements in some chromosome pairs. Individuals of T. noronhanum (between the insular regions of Rocas Atoll and Fernando de Noronha Archipelago - FNA) and H. poeyi (coastal areas from Northeastern Brazil) show no detectable differences among their cytogenetic patterns. On the other hand, H. radiatus from FNA and São Pedro and São Paulo Archipelago exhibit differences in the frequency of rDNA sites that could suggest some level of population structuring between these insular regions. Interregional cytogenetic inventories of marine species with wide geographic distribution need to be rapidly expanded. These data will allow a better understanding of the level of chromosomal stability between vast oceanic spaces, which may be less than previously thought.
海洋生物多样性的分布模式很复杂，这是由地理隔离事件、物种扩散以及当地生态和适应条件造成的。此外，某些物种广泛的地理分布可能会受到生物地理屏障的阻碍，这些屏障会干扰基因流动。对海洋鱼类进行细胞遗传学分析仍然很少，尤其是那些涉及偏远小岛屿环境中种群的分析。在西大西洋，海猪鱼属（Halichoeres）和锦鱼属（Thalassoma）的隆头鱼物种呈现出生物地理分布格局，这使得分析沿海和相距甚远的岛屿种群之间的细胞遗传学模式成为可能。在一些大西洋地区对这些属的物种进行了零散的分析。在本研究中，我们比较了来自大西洋不同沿海或岛屿地区的诺氏锦鱼（Thalassoma noronhanum）、波氏海猪鱼（Halichoeres poeyi）和辐射海猪鱼（Halichoeres radiatus）个体的几个染色体特征，如核型宏观结构、异染色质模式、碱基特异性荧光染料模式、银染核仁组织区（Ag-NORs）以及18S和5S核糖体位点。值得注意的是，它们都具有多个18S和5S rDNA位点，并且在一些染色体对中存在同线排列。诺氏锦鱼（在罗卡斯环礁和费尔南多·迪诺罗尼亚群岛——FNA的岛屿地区之间）和波氏海猪鱼（巴西东北部沿海地区）的个体在细胞遗传学模式上没有可检测到的差异。另一方面，来自FNA以及圣佩德罗和圣保罗群岛的辐射海猪鱼在rDNA位点频率上存在差异，这可能表明这些岛屿地区之间存在一定程度的种群结构。需要迅速扩大对具有广泛地理分布的海洋物种的区域间细胞遗传学清查。这些数据将有助于更好地了解广阔海洋空间之间染色体稳定性的水平，这可能比之前认为的要低。
