Oliveira Isabel Araújo, Argolo Leandro Araújo, Bitencourt Jamille de Araújo, Diniz Débora, Vicari Marcelo Ricardo, Affonso Paulo Roberto Antunes de Mello
1 Departamento de Ciências Biológicas, Laboratório de Citogenética, Universidade Estadual do Sudoeste da Bahia , Jequié, Bahia, Brazil .
2 Departamento de Biologia Estrutural, Molecular e Genética, Universidade Estadual de Ponta Grossa , Ponta Grossa, Paraná, Brazil .
Zebrafish. 2016 Feb;13(1):33-44. doi: 10.1089/zeb.2015.1169. Epub 2015 Dec 18.
Among American cichlids, Geophagus stands out as a species-rich genus widespread over neotropical region. Despite their diversity and confusing taxonomy, only few and basic chromosomal reports are available in populations/species along Atlantic coast, hindering our understanding about evolutionary trends in this genus. Therefore, detailed chromosomal studies were performed in "Geophagus" brasiliensis complex from coastal rivers in northeastern Brazil, totalizing seven populations of Geophagus brasiliensis and one of Geophagus itapicuruensis. All samples shared a diploid number (2n) of 48 divided into 2 submetacentric and 46 subtelocentric/acrocentric chromosomes with (peri)centromeric heterochromatin, hypothesized as a symplesiomorphy for Geophagini. Although G. itapicuruensis and two populations of G. brasiliensis presented single NORs on short arms, multiple GC-rich rDNA sites were observed in the remaining G. brasiliensis samples, ranging from three to six NOR-bearing chromosomes. Inversely, 5S rDNA sites were invariably located at interstitial region on a st/a pair, nonsyntenic to NORs. A compilation of the data set in Geophagus shows that their chromosomal evolution has been driven by pericentric inversions and microstructural changes. Besides, the divergence found in northeastern Brazil places this region as a biodiversity hotspot. A taxonomic revision in the complex "Geophagus" brasiliensis is recommended with the support of cytogenetic analyses.
在美洲丽鱼科鱼类中，土丽鱼属是一个物种丰富的属，广泛分布于新热带地区。尽管它们种类多样且分类混乱，但关于大西洋沿岸种群/物种的染色体报告却很少且基础，这阻碍了我们对该属进化趋势的理解。因此，我们对巴西东北部沿海河流中的巴西土丽鱼复合体进行了详细的染色体研究，总共研究了7个巴西土丽鱼种群和1个伊塔皮库鲁土丽鱼种群。所有样本的二倍体数目（2n）均为48，分为2条亚中着丝粒染色体和46条亚端着丝粒/近端着丝粒染色体，带有（近）着丝粒异染色质，推测这是土丽鱼科的一个共近裔性状。尽管伊塔皮库鲁土丽鱼和两个巴西土丽鱼种群在短臂上呈现单个核仁组织区（NOR），但在其余的巴西土丽鱼样本中观察到多个富含GC的核糖体DNA（rDNA）位点，范围从3条到6条带有NOR的染色体。相反，5S rDNA位点总是位于一对st/a染色体的中间区域，与NOR不同源。对土丽鱼属数据集的汇总表明，它们的染色体进化是由着丝粒倒位和微观结构变化驱动的。此外，在巴西东北部发现的差异使该地区成为一个生物多样性热点。建议在细胞遗传学分析的支持下，对巴西土丽鱼复合体进行分类修订。
