Gavazzoni Mariane, Paiz Leonardo M, Oliveira Carlos A M, Pavanelli Carla S, Graça Weferson J, Margarido Vladimir P
1 Centro de Ciências Biológicas e da Saúde , Universidade Estadual do Oeste do Paraná, Cascavel, Paraná, Brazil .
2 Pós Graduação em Biologia Comparada, Universidade Estadual de Maringá , Maringá, Paraná, Brazil .
Zebrafish. 2018 Aug;15(4):382-388. doi: 10.1089/zeb.2018.1574. Epub 2018 Apr 10.
Astyanax is a species-rich polyphyletic genus distributed between the southern United States and central Argentina. The genus contains groups of cryptic species, which are difficult to distinguish, and are sometimes identified wrongly. Basic and molecular cytogenetic analyses were run on Astyanax abramis and three junior synonyms of Astyanax lacustris: Astyanax altiparanae, from the upper Paraná River basin, Astyanax asuncionensis, from the lower Paraná basin, and Astyanax jacuhiensis, from the upper Uruguay River. These species all belong to the Astyanax bimaculatus group. All species presented 2n = 50 chromosomes and single nucleolar organizing regions (NORs). In A. altiparanae, the karyotype was 6m + 28sm+4st+12a and the NORs were present in pair 20, while A. jacuhiensis was 8m + 28sm+6st+8a, with NORs in pair 22, and A. asuncionensis was 8m + 24sm+6st+12a, with NORs in pair 20. A. abramis was 4m + 30sm+8st+8a with NORs in pair 22. Fluorescence in situ hybridization revealed single 5S rDNA cistrons in A. altiparanae and A. asuncionensis, and multiple (4) cistrons in A. abramis and A. jacuhiensis. Heterochromatin had a distinct distribution in each species, but was predominantly centromeric and interstitial proximal. In A. abramis and A. asuncionensis, the first acrocentric chromosome pair presented centromeric, telomeric, and interstitial-proximal heterochromatin in the long arm, which may represent the presence of homologous chromosomes in these species. While there are some cytogenetic similarities, differences in the location of 5S rDNA, distribution of heterochromatin, and karyotype formulae contribute to the differentiation of the study species, and support the identification of phylogenetically proximate groups in the "Astyanax clade."
丽脂鲤属是一个物种丰富的多系属，分布于美国南部和阿根廷中部之间。该属包含一些难以区分的隐存物种群，有时会被错误识别。对阿氏丽脂鲤以及湖栖丽脂鲤的三个次异名进行了基础和分子细胞遗传学分析：来自巴拉那河上游流域的高巴拉那丽脂鲤、来自巴拉那河下游流域的亚松森丽脂鲤以及来自乌拉圭河上游的雅库希丽脂鲤。这些物种均属于双斑丽脂鲤组。所有物种的染色体数目均为2n = 50，且具有单个核仁组织区（NORs）。在高巴拉那丽脂鲤中，核型为6m + 28sm + 4st + 12a，NORs位于第20对染色体上；而雅库希丽脂鲤的核型为8m + 28sm + 6st + 8a，NORs位于第22对染色体上；亚松森丽脂鲤的核型为8m + 24sm + 6st + 12a，NORs位于第20对染色体上。阿氏丽脂鲤的核型为4m + 30sm + 8st + 8a，NORs位于第22对染色体上。荧光原位杂交显示，高巴拉那丽脂鲤和亚松森丽脂鲤中有单个5S rDNA顺反子，而阿氏丽脂鲤和雅库希丽脂鲤中有多个（4个）顺反子。异染色质在每个物种中的分布都不同，但主要位于着丝粒和近侧间区。在阿氏丽脂鲤和亚松森丽脂鲤中，第一对近端着丝粒染色体的长臂上呈现着丝粒、端粒和近侧间区异染色质，这可能表明这些物种中存在同源染色体。虽然存在一些细胞遗传学上的相似性，但5S rDNA的位置、异染色质的分布以及核型公式的差异有助于区分所研究的物种，并支持在“丽脂鲤进化枝”中识别亲缘关系较近的类群。
