Gymnotus属是淡水弱电鱼类的大型单系类群,在中美洲和南美洲广泛分布。它有46个有效物种,分为六个亚属(Gymnotus,Tijax,蒂格雷,Lamontianus,Tigrinus和Pantherus)具有较大的染色体可塑性和二倍体数(2n),范围为34至54。在这种丰富的多样性中,关于Gymnotus(Gymnotus)carapo物种是单一的广泛物种还是神秘物种的复合体存在争议。细胞遗传学研究显示G.carapo物种的二倍体数量不同,甚至在共享相同2n的种群之间也发现了具有不同核型的40至54条染色体。全染色体绘画已用于鱼类物种的研究,最近已用于跟踪Gymnotus的染色体进化并协助其细胞分类学。使用染色体绘画的比较基因组作图显示,与经典细胞遗传学的先前研究相比,Gymnotuscarapo的重排更为复杂。这些研究表明,多个染色体对参与其染色体重组,表明由于合子后屏障而存在隐秘物种的复合物。在本研究中,西卡拉坡的中期染色体“catalão”(GCC,2n=40,30m/sm+10st/a)来自加泰罗尼亚湖,亚马逊,巴西,与来自G.carapo染色体的全染色体探针杂交(GCA,2n=42,30m/sm+12st/a)。结果显示染色体重排和大量重复DNA位点。在可以单独鉴定的12对G.carapo染色体中(GCA1-3、6、7、9、14、16和18-21),8对(GCA1、2、6、7、9、14、20、21)在GCC中具有保守的同源性。在分组的GCA对中(GCA[4,8],[5,17],[10,11]和[12,13,15]),大多数保持在GCC中的信号数量(GCA[5,17],[10,11]和[12,13,15])。其余染色体在GCC核型中重排。对两个G.carapo细胞型种群的分析显示出广泛的核型重组。除了以前的研究,这表明,这里分析的不同的细胞类型可能代表不同的物种,并支持G.carapo不是一个单一的广泛物种的假设,而是一群神秘的物种。
The genus Gymnotus 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 (Gymnotus, Tijax, Tigre, Lamontianus, Tigrinus and Pantherus) with large chromosome plasticity and diploid numbers (2n) ranging from 34 to 54. Within this rich diversity, there is controversy about whether Gymnotus (Gymnotus) carapo species is a single widespread species or a complex of cryptic species. Cytogenetic studies show different diploid numbers for G. carapo 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 Gymnotus and assisting in its cytotaxonomy. Comparative genomic mapping using chromosome painting has shown more complex rearrangements in Gymnotus carapo 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 G. carapo occidentalis \"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 G. carapo (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 G. carapo 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 G. carapo 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 G. carapo is not a single widespread species, but a group of cryptic species.