dos Santos Silva Danillo, Milhomem Susana Suely Rodrigues, de Souza Augusto Cezar Paes, Pieczarka Julio Cesar, Nagamachi Cleusa Yoshiko
Bolsista CAPES de Mestrado em Genética e Biologia Molecular, Brazil.
Micron. 2008 Dec;39(8):1251-4. doi: 10.1016/j.micron.2008.04.001. Epub 2008 Apr 12.
We studied the karyotypes of 35 Sternopygus macrurus fishes of four localities from rivers of the Eastern Amazon basin. In these four places the karyotypes have 2n=46 chromosomes, NF=92, where 30 are metacentric (M) and 16 submetacentric (SM). The constitutive heterochromatin (CH) is found in the centromeric region of most chromosomes and in the pericentromeric region of pairs 5, 17 and 19. Pair 1 has a large and not common heterochromatic block in the short arm, useful as a marker for this species if not found in other Sternopygus taxa. The NOR is located in the distal region of the short arm of pair 1, showing a size heteromorphism in some specimens. The CMA(3) and DAPI fluorochrome bandings and the fluorescent in situ hybridization (FISH), using pantelomeric human probes techniques are described for the first time for this species. DAPI has banding coincident with the C-banded regions, which suggests that the CH is AT base-pair-rich. CMA(3) banding is coincident with the NOR, meaning that this region is GC base-pair-rich. The FISH showed that the probes hybridized only with the telomeric regions, without any sign of interstitial telomeric regions. The karyotype of the samples from different places in the Amazon basin is quite conserved, probably because of the gene flow among the populations. The karyotype differences among the Sternopygus macrurus from the Amazon basin and the São Francisco and Paraná rivers suggest that these taxa may be different species.
我们研究了来自亚马逊东部流域河流四个地点的35条大吻电鳗的核型。在这四个地点，核型具有2n = 46条染色体，NF = 92，其中30条为中着丝粒染色体（M），16条为亚中着丝粒染色体（SM）。组成型异染色质（CH）存在于大多数染色体的着丝粒区域以及第5、17和19对染色体的近着丝粒区域。第1对染色体在短臂上有一个大的且不常见的异染色质块，如果在其他大吻电鳗分类群中未发现，可作为该物种的一个标记。核仁组织区（NOR）位于第1对染色体短臂的远端区域，在一些标本中显示出大小多态性。首次描述了该物种使用人端粒探针技术的CMA(3)和DAPI荧光带型以及荧光原位杂交（FISH）。DAPI带型与C带区域一致，这表明CH富含AT碱基对。CMA(3)带型与NOR一致，意味着该区域富含GC碱基对。FISH显示探针仅与端粒区域杂交，没有任何中间端粒区域的迹象。亚马逊流域不同地点样本的核型相当保守，可能是由于种群间的基因流动。来自亚马逊流域与圣弗朗西斯科河和巴拉那河的大吻电鳗之间的核型差异表明这些分类群可能是不同的物种。
