Aichino D R, Pastori M C, Roncati H A, Ledesma M A, Swarça A C, Fenocchio A S
Departamento de Genetica, Facultad de Ciencias Exactas, Químicas y Naturales, Universidad Nacional de Misiones, Posadas, Misiones, Argentina.
Genet Mol Res. 2013 Jul 8;12(3):2368-75. doi: 10.4238/2013.January.16.3.
The Potamotrygonidae family represents the only freshwater group of specialized elasmobranchs and is composed of 4 genera: Plesiotrygon, Paratrygon, Potamotrygon, and Heliotrygon. Individuals of Potamotrygon motoro were collected from the Paraná River at Ituzaingó (Province of Corrientes) in Argentina. Mitotic preparations were obtained using direct techniques and lymphocyte cultures. Chromosomes were studied with conventional Giemsa, C-band and nucleolus organizer region stainings. The diploid number and karyotype formulae were 2n = 66 with 33 homomorphic pairs (14M + 16SM + 22ST + 14A) in females and 2n = 65 with 31 homomorphic pairs plus 3 heteromorphic chromosomes (13M + 15SM + 23ST + 14A) in males. Heterochromatin was distributed at the pericentromeric regions of almost all chromosomes and in the telomeric and interstitial positions of some chromosomes. nucleolus organizer regions were multiple and located at telomeric regions. Because of the clear karyotype differences between the 2 sexes and the presence of 3 unpaired chromosomes in males, it is possible to suggest the occurrence of a multiple sex chromosome system, with male heterogamety (X1X1X2X2/X1X2Y). Further cytogenetic studies are required to develop a hypothesis about the origin of the multiple sex chromosome system in P. motoro.
电鲼科是唯一的淡水特化板鳃鱼类群，由4个属组成：近电鲼属、副电鲼属、电鲼属和太阳电鲼属。阿根廷科连特斯省伊图萨因戈的巴拉那河采集了电鲼个体。采用直接技术和淋巴细胞培养获得有丝分裂标本。用常规吉姆萨染色、C带染色和核仁组织区染色研究染色体。雌性二倍体数和核型公式为2n = 66，有33对同形染色体对（14M + 16SM + 22ST + 14A），雄性二倍体数为2n = 65，有31对同形染色体对加3条异形染色体（13M + 15SM + 23ST + 14A）。异染色质分布在几乎所有染色体的着丝粒周围区域以及一些染色体的端粒和中间位置。核仁组织区多个且位于端粒区域。由于两性之间明显的核型差异以及雄性中存在3条不成对的染色体，有可能推测存在多性染色体系统，雄性为异配性别（X1X1X2X2/X1X2Y）。需要进一步的细胞遗传学研究来提出关于电鲼多性染色体系统起源的假说。
