Lanzone C, Rodríguez D, Cuello P, Albanese S, Ojeda A, Chillo V, Martí D A
Grupo de Investigaciones de la Biodiversidad, IADIZA, CONICET, CCT-Mendoza, CC 507, CP5500 Mendoza, Argentina.
Genetica. 2011 Sep;139(9):1143-7. doi: 10.1007/s10709-011-9616-7. Epub 2011 Nov 22.
Salinomys delicatus is considered a rare species due to its restricted and patchy distribution, poor records and low abundances. It is also the phyllotine with the lowest known diploid chromosome number (2n = 18), however its sex chromosome system has never been described. Here, we studied the chromosomes of six females and three males with bands G, C, DAPI/CMA(3) and meiosis. In males, the chromosome number was 2n = 19, with one large metacentric X-chromosome and two medium-sized acrocentrics absent in females. The karyotype of females was the same as previously described (2n = 18, FN = 32), with X-chromosomes being metacentric and the largest elements of the complement. In males, the two acrocentrics and the large metacentric form a trivalent in meiotic prophase. This indicates that S. delicatus has XY(1)Y(2) sex chromosomes, which is confirmed by G and DAPI bands. Constitutive heterochromatin (CH) is restricted to small pericentromeric blocks in all chromosomes. The X-chromosome shows the largest block of centromeric CH, which could favor the establishment of this X-autosome translocation. This sex chromosome system is rare in mammals and, compared with other phyllotine rodents, S. delicatus seems to have undergone a major chromosome restructuring during its karyotypic evolution.
细弱盐鼠因分布范围有限且不连续、记录稀少以及数量稀少而被视为稀有物种。它也是已知二倍体染色体数最低（2n = 18）的叶鼻鼠，但从未有人描述过它的性染色体系统。在此，我们通过G、C、DAPI/CMA(3)带型以及减数分裂研究了6只雌性和3只雄性的染色体。雄性的染色体数为2n = 19，有一条大的中着丝粒X染色体和两条中等大小的近端着丝粒染色体，而雌性没有这两条近端着丝粒染色体。雌性的核型与之前描述的相同（2n = 18，FN = 32），X染色体为中着丝粒染色体，是染色体组中最大的染色体。在雄性中，两条近端着丝粒染色体和大的中着丝粒染色体在减数分裂前期形成三价体。这表明细弱盐鼠具有XY(1)Y(2)性染色体，G带和DAPI带型证实了这一点。组成型异染色质（CH）局限于所有染色体的小的着丝粒周围区域。X染色体显示出最大的着丝粒CH区域，这可能有利于这种X - 常染色体易位的形成。这种性染色体系统在哺乳动物中很罕见，并且与其他叶鼻鼠相比，细弱盐鼠在其核型进化过程中似乎经历了一次重大的染色体重组。
