Piscor Diovani, Pozzobon Allan Pierre Bonetti, Fernandes Carlos Alexandre, Centofante Liano, Parise-Maltempi Patricia Pasquali
1 Laboratório de Citogenética, Departamento de Biologia, Instituto de Biociências, Universidade Estadual Paulista "Júlio de Mesquita Filho" (UNESP), Rio Claro, Brazil.
2 Universidade Estadual de Mato Grosso do Sul (UEMS), Unidade de Mundo Novo, Mundo Novo, Brazil.
Zebrafish. 2019 Feb;16(1):98-105. doi: 10.1089/zeb.2018.1647. Epub 2018 Oct 24.
Astyanax is a genus with a wide distribution ranging from the south United States to north of Patagonia (Argentina). The available cytogenetic data on Astyanax indicate a high karyotypic diversity, with diploid number of 36-52 chromosomes, presence of B chromosomes, heterochromatin polymorphism, and variations with respect to the number and localization of nucleolar organizer regions (NORs) and 18S and 5S ribosomal DNA sites. In the present study, we estimated the evolutionary history and times of divergence for 10 nominal Astyanax species from the South and Central/North American (Cna) continents, which present distinct chromosomal characteristics, based on molecular clocks inferred from mitochondrial DNA sequence. The molecular clock results indicate the origin of three distinct clades (Humeral dark spot [Hds]; Diffuse humeral spot [Dhs]; Cna group) during the late Miocene about 11.2 million years ago (Mya). Thus, Astyanax mexicanus (Cna) represent a species that diverged a long time ago (∼8.6 Mya) from the Hds group, and Astyanax schubarti is the oldest species (∼6.5 Mya) among the Dhs species.
阿氏霓虹脂鲤属分布广泛，范围从美国南部到巴塔哥尼亚（阿根廷）北部。现有的关于阿氏霓虹脂鲤属的细胞遗传学数据表明其核型多样性很高，二倍体染色体数为36 - 52条，存在B染色体、异染色质多态性，以及核仁组织区（NORs）和18S及5S核糖体DNA位点在数量和定位上的变异。在本研究中，我们基于从线粒体DNA序列推断出的分子钟，估计了来自南美洲和中美洲/北美洲（Cna）大陆的10个名义阿氏霓虹脂鲤物种的进化历史和分歧时间，这些物种具有不同的染色体特征。分子钟结果表明，在约1120万年前（百万年前，Mya）的中新世晚期出现了三个不同的进化枝（肱部黑斑[Hds]；弥散肱部黑斑[Dhs]；Cna组）。因此，墨西哥阿氏霓虹脂鲤（Cna）代表了一个很久以前（约860万年前）就与Hds组分歧的物种，而舒氏阿氏霓虹脂鲤是Dhs物种中最古老的物种（约650万年前）。
