Vidotto A P, Swarça A C, Fenocchio A S, Dias A L
Universidade Estadual de Londrina, Depto. de Biologia Geral, Londrina, PR, Brazil, 86051-970, Caixa Postal 6001.
J Hered. 2004 Nov-Dec;95(6):517-20. doi: 10.1093/jhered/esh075.
We analyzed cytogenetically specimens of Pimelodella meeki from Tibagi River at Limoeiro (LM) and from two tributaries, Couro do Boi (CB) and Gabriel da Cunha (GC) Rivers. All specimens presented 2n=46 chromosomes, which were the karyotypes composed by 15 pairs metacentric (M) + 6 pairs submetacentric (SM) + 2 pairs subtelocentric (ST). In specimens of GC, CB, and LM, the results of analyses of the nucleolus organizer regions (NORs), done by means of AgNO3 and CMA3 staining, showed that they are identical, located in terminal position on the short arm of a SM chromosome pair, and they were observed to be a size heteromorphism in some metaphase plates. FISH with 18S rDNA probe yielded evidence for these regions but not for the size variation, indicating that they are not due to a greater number of NOR cistrons in one of the homologue chromosomes. An interesting characteristic of these regions is that they could appear divided in blocks, as evidenced by all the techniques. This work makes clear the necessity for more deeply systematic studies, because of the confused taxonomic situation of the genus Pimelodella.
我们对来自利莫埃罗（LM）蒂巴吉河以及两条支流库罗多博伊（CB）河和加布里埃尔达库尼亚（GC）河的米氏油鲶的细胞遗传学标本进行了分析。所有标本均呈现2n = 46条染色体，其核型由15对中着丝粒染色体（M）+ 6对亚中着丝粒染色体（SM）+ 2对亚端着丝粒染色体（ST）组成。在GC、CB和LM的标本中，通过硝酸银（AgNO₃）和CMA₃染色对核仁组织区（NORs）进行分析的结果表明，它们是相同的，位于一对SM染色体短臂的末端位置，并且在一些中期板中观察到它们存在大小异质性。用18S rDNA探针进行荧光原位杂交（FISH）为这些区域提供了证据，但未发现大小变异，这表明它们并非由于同源染色体之一中NOR顺反子数量更多所致。这些区域的一个有趣特征是，正如所有技术所证明的那样，它们可能呈现为块状分隔。由于油鲶属的分类情况混乱，这项工作明确了进行更深入系统研究的必要性。
