Ortells M O, Reig O A, Brum-Zorrilla N, Scaglia O A
Departamento de Ciencias Biologicas, Universidad de Buenos Aires, Argentina.
Genetica. 1988 Jul 31;77(1):53-63. doi: 10.1007/BF00058549.
The chromosomes of 14 specimens of the genus Reithrodon from three different localities of Argentina and two localities of Uruguay were studied using G- and C-banding techniques. Specimens of Uruguay showed a karyotype of 2n = 28 chromosomes having a large metacentric X, and a telocentric Y chromosome. This karyotype is very similar to that recently described in a sample from southern Brazil, differing only in the nature of the Y chromosome, which is metacentric in the Brazilian form. All specimens from Argentina showed a 2n = 34 karyotype, differing from the Brazilian karyotype by two centric fusions, an acquisition of chromosome material, and at least one pericentric inversion, and by the telocentric nature of both the X and the Y chromosomes. G- and C-banding suggest that the metacentric gonosomes in the Brazilian form resulted from a double autosomal-X-Y Robertsonian translocation. The Uruguayan cytotype is interpreted as derived from a hypothetical neo-X/Y1Y2 ancestral form by the secondary loss of the Y1 chromosome. The karyotypic differences between the Brazilian-Uruguayan and the Argentinian forms afford evidence of species differentiation. It is proposed to assign the former to Reithrodon typicus, and the later to R. auritus.
利用G带和C带技术，对来自阿根廷三个不同地点和乌拉圭两个地点的14个稻鼠属标本的染色体进行了研究。乌拉圭的标本显示其核型为2n = 28条染色体，有一条大的中着丝粒X染色体和一条端着丝粒Y染色体。这种核型与最近在巴西南部一个样本中描述的非常相似，只是Y染色体的性质不同，在巴西的样本中Y染色体是中着丝粒的。所有来自阿根廷的标本都显示出2n = 34的核型，与巴西核型的差异在于两次着丝粒融合、染色体物质的获得、至少一次臂间倒位，以及X和Y染色体均为端着丝粒的性质。G带和C带分析表明，巴西样本中的中着丝粒性染色体是由两次常染色体 - X - Y罗伯逊易位产生的。乌拉圭的细胞型被解释为是通过Y1染色体的二次丢失，从一个假设的新X/Y1Y2祖先形式衍生而来的。巴西 - 乌拉圭型和阿根廷型之间的核型差异为物种分化提供了证据。建议将前者归为典型稻鼠（Reithrodon typicus），后者归为金色稻鼠（R. auritus）。
