Machado Milla de Andrade, da Silva Maelin, Feldberg Eliana, O'Brien Patricia Caroline Mary, Ferguson-Smith Malcolm Andrew, Pieczarka Julio Cesar, Nagamachi Cleusa Yoshiko
Laboratório de Citogenética, Centro de Estudos Avançados da Biodiversidade, Instituto de Ciências Biológicas, Universidade Federal Do Pará (UFPA), Belém, Brazil.
Departamento de Biologia Estrutural, Molecular e Genética, Universidade Estadual de Ponta Grossa, Ponta Grossa, Brazil.
Front Genet. 2022 Mar 24;13:832495. doi: 10.3389/fgene.2022.832495. eCollection 2022.
The genus is a large monophyletic group of freshwater weakly-electric fishes, with wide distribution in Central and South America. It has 46 valid species divided into six subgenera (, , , , and ) with large chromosome plasticity and diploid numbers (2n) ranging from 34 to 54. Within this rich diversity, there is controversy about whether () species is a single widespread species or a complex of cryptic species. Cytogenetic studies show different diploid numbers for species, ranging from 40 to 54 chromosomes with varied karyotypes found even between populations sharing the same 2n. Whole chromosome painting has been used in studies on fish species and recently has been used for tracking the chromosomal evolution of and assisting in its cytotaxonomy. Comparative genomic mapping using chromosome painting has shown more complex rearrangements in than shown in previous studies by classical cytogenetics. These studies demonstrate that multiple chromosome pairs are involved in its chromosomal reorganization suggesting the presence of a complex of cryptic species due to a post zygotic barrier. In the present study, metaphase chromosomes of "catalão" (GCC, 2n = 40, 30m/sm+10st/a) from the Catalão Lake, Amazonas, Brazil, were hybridized with whole chromosome probes derived from the chromosomes of (GCA, 2n = 42, 30m/sm+12st/a). The results reveal chromosome rearrangements and a high number of repetitive DNA sites. Of the 12 pairs of chromosomes that could be individually identified (GCA 1-3, 6, 7, 9, 14, 16 and 18-21), 8 pairs (GCA 1, 2, 6, 7, 9, 14, 20, 21) had homeology conserved in GCC. Of the GCA pairs that are grouped (GCA [4, 8], [5, 17], [10, 11] and [12, 13, 15]), most kept the number of signals in GCC (GCA [5, 17], [10, 11] and [12, 13, 15]). The remaining chromosomes are rearranged in the GCC karyotype. Analysis of both populations of the cytotypes shows extensive karyotype reorganization. Along with previous studies, this suggests that the different cytotypes analyzed here may represent different species and supports the hypothesis that is not a single widespread species, but a group of cryptic species.
该属是淡水弱电鱼的一个大型单系类群，在中美洲和南美洲分布广泛。它有46个有效物种，分为六个亚属（、、、、和），具有较大的染色体可塑性，二倍体数目（2n）从34到54不等。在这种丰富的多样性中，关于（）物种是单一的广布种还是隐存种复合体存在争议。细胞遗传学研究表明，物种的二倍体数目不同，染色体数目从40到54条不等，甚至在具有相同2n的种群之间也发现了不同的核型。全染色体涂染已用于鱼类物种研究，最近也用于追踪的染色体进化并辅助其细胞分类学。使用染色体涂染的比较基因组图谱显示，中的重排比经典细胞遗传学先前研究中显示的更为复杂。这些研究表明，多个染色体对参与了其染色体重组，这表明由于合子后屏障的存在，存在一个隐存种复合体。在本研究中，来自巴西亚马孙州卡塔朗湖的“卡塔朗”（GCC，2n = 40，30m/sm + 10st/a）中期染色体与来自（GCA，2n = 42，30m/sm + 12st/a）染色体的全染色体探针进行杂交。结果揭示了染色体重排和大量重复DNA位点。在12对可单独识别的染色体（GCA 1 - 3、6、7、9、14、16和18 - 21）中，8对（GCA 1、2、6、7、9、14、20、21）在GCC中具有保守的同源性。在成组的GCA对（GCA [4, 8]、[5, 17]、[10, 11]和[12, 13, 15]）中，大多数在GCC中保持信号数量（GCA [5, 17]、[10, 11]和[12, 13, 15]）。其余染色体在GCC核型中发生重排。对两种细胞型种群的分析显示出广泛的核型重组。与先前的研究一起，这表明这里分析的不同细胞型可能代表不同的物种，并支持不是单一广布种而是一组隐存种的假设。
