Fernandes Carlos Alexandre, Paiz Leonardo Marcel, Baumgärtner Lucas, Margarido Vladimir Pavan, Vieira Margarida Maria de Rossi
1 Universidade Estadual de Mato Grosso do Sul, Unidade Universitária de Mundo Novo , Mato Grosso do Sul, Brazil .
2 Centro de Ciências Biológicas, Universidade Estadual de Maringá , Maringá, Paraná, Brazil .
Zebrafish. 2017 Oct;14(5):471-476. doi: 10.1089/zeb.2017.1432. Epub 2017 May 30.
The karyotype and chromosomal characteristics of Apteronotus albifrons and Apteronotus caudimaculosus collected from populations of two different large Brazilian river basins were analyzed by conventional and molecular cytogenetic techniques, to contribute to the differentiation and identification of the species in this genus. The diploid chromosome number was 2n = 24 for A. albifrons, but with difference in the karyotype structure and fundamental number values between two populations under study. In A. caudimaculosus, the diploid chromosome number was 2n = 26, which was classified as 22 metacentric (m), 2 submetacentric (sm), and 2 acrocentric (a) chromosomes. Heterochromatins were preferentially located in pericentromeric regions for both species. However, there are more C-banded chromosomes in A. caudimaculosus than A. albifrons. The sites of 18S DNA as revealed by fluorescence in situ hybridization (FISH) in the karyotypes of both species corresponded to sites revealed by Ag impregnation, although some additional 18S rDNA sites were observed in the genome of A. caudimaculosus. FISH with 5S rDNA-probe revealed interstitial sites on the m pair No. 1 for individuals of both A. albifrons populations, and in pericentromeric regions on the long arm of pair Nos. 5 and 9 in those of A. caudimaculosus. The karyotypes of A. albifrons and A. caudimaculosus indicated a reduction of 2n resulting from chromosomal fusion, as could be hypothesized from the presence of an interstitial telomere sequence in two chromosome pairs in karyotype of A. caudimaculosus. Thus, the present study demonstrated species-specific cytogenetic markers of otherwise morphologically very similar species A. albifrons and A. caudimaculosus.
采用传统和分子细胞遗传学技术，分析了从巴西两个不同大流域种群采集的白边光背电鳗和尾斑光背电鳗的核型及染色体特征，以促进该属物种的分化和鉴定。白边光背电鳗的二倍体染色体数为2n = 24，但所研究的两个种群在核型结构和基数数值上存在差异。尾斑光背电鳗的二倍体染色体数为2n = 26，可分为22条中着丝粒染色体（m）、2条亚中着丝粒染色体（sm）和2条近端着丝粒染色体（a）。两种电鳗的异染色质均优先位于着丝粒周围区域。然而，尾斑光背电鳗中C带染色体比白边光背电鳗更多。荧光原位杂交（FISH）显示，两种电鳗核型中18S DNA的位点与银染显示的位点相对应，不过在尾斑光背电鳗的基因组中观察到了一些额外的18S rDNA位点。用5S rDNA探针进行FISH分析发现，白边光背电鳗两个种群个体的第1对中着丝粒染色体上存在居间位点，而尾斑光背电鳗个体的第5和9对染色体长臂的着丝粒周围区域存在居间位点。白边光背电鳗和尾斑光背电鳗的核型表明，染色体融合导致2n减少，这可以从尾斑光背电鳗核型中两条染色体对存在居间端粒序列推测出来。因此，本研究证明了形态上非常相似的白边光背电鳗和尾斑光背电鳗具有物种特异性的细胞遗传学标记。
