Cytogenetic data for the genus Cichla Bloch et Schneider, 1801 are still very limited, with only four karyotype descriptions to date. The sum of the available cytogenetic information for Cichla species, points to a maintenance of the diploid number of 48 acrocentric chromosomes, considered a typical ancestral feature in cichlids. In the current study, we performed molecular and classical cytogenetic analyses of the karyotype organization of six species of Cichla, the earliest-diverging genus of Neotropical cichlids. We cytogenetically analysed Cichla kelberi Kullander et Ferreira, 2006, Cichla monoculus Agassiz, 1831, Cichla piquiti Kullander et Ferreira, 2006, Cichla temensis Humboldt, 1821, Cichla vazzoleri Kullander et Ferreira, 2006 and Cichla pinima Kullander et Ferreira, 2006, including three individuals that showed mixed morphological characteristics, likely from different species, suggesting they were hybrid individuals. All individuals analysed showed 2n = 48 acrocentric chromosomes, with centromeric heterochromatic blocks on all chromosomes and a terminal heterochromatic region on the q arm of the 2nd pair. Mapping 18S rDNA gave hybridization signals, correlated with the nucleolus organizer regions, on the 2nd pair for all analyzed individuals. However, we found distinct patterns for 5S rDNA: interstitially at the proximal position on 6th pair of four species (C. kelberi, C. pinima, C. piquiti and C. vazzoleri), and on the distal of the 4th pair in two (C. monoculus and C. temensis). Accordingly, we present here new data for the genus and discuss the evolutionary trends in the karyotype of this group of fish. In addition, we provide data that supports the occurrence of hybrid individuals in the Uatumã River region, mainly based on 5S rDNA mapping.

中文翻译：

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六种亚马逊孔雀鲈（Cichla，Cichlinae）的比较细胞遗传学：同胞种之间的染色体内变异和遗传渗入

Cichla Bloch et Schneider，1801属的细胞遗传学数据仍然非常有限，迄今为止仅描述了四个核型。丽鱼科物种可获得的细胞遗传学信息的总和表明维持了48个顶心染色体的二倍体数，这被认为是丽鱼科动物的典型祖先特征。在当前的研究中，我们进行了分子和经典细胞遗传学分析的六个物种的慈鲷的核型组织，这是新热带慈鲷的最早分化属。我们用细胞遗传学方法分析了Cichla kelberi Kullander et Ferreira，2006，Cichla monoculus Agassiz，1831，Cichla piquiti Kullander et Ferreira，2006，Cichla temensis Humboldt，1821，Cichla vazzoleri Kullander et Ferreira，2006和Cichla pinima Kullander et Ferreira，2006。包括三个具有不同形态特征的个体，可能来自不同物种，这表明它们是杂种个体。分析的所有个体均显示2n = 48个顶心染色体，所有染色体上均存在着着丝粒异色块，第二对的q臂上有末端异色区域。映射18S rDNA在所有分析的个体的第二对上均给出了与核仁组织者区域相关的杂交信号。但是，我们发现了5S rDNA的不同模式：间隙地位于四个物种的第6对对（C. kelberi，C。pinima，C。piquiti和C. vazzoleri），以及第4对的远端（两个） C. monoculus和C. temensis）。因此，我们在此提供该属的新数据，并讨论这组鱼的核型的进化趋势。