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Cytogenetic analyses were performed in four species of the Hypostominae subfamily, three from Hypostomus (Hypostomini) genus and Rhinelepis aspera (Rhinelepini). Three populations of Hypostomus ancistroides were analyzed, which had 2n=68 chromosomes, but presented different karyotype formulas. Hypostomus regani and H. strigaticeps, both from Ivaí river, showed 2n=72 chromosomes with two distinct cytotypes. In turn, R. aspera of the upper Paraná river basin presented 2n=54 chromosome. Multiple Nucleolar Organizer Regions (NORs) have been evidenced by silver nitrate staining in species of Hypostomus and single NOR in R. aspera. The observed variation in the chromosome number and the marked variability in karyotype formulas and NORs reveal a certain amount of karyotype variation in the genus Hypostomus suggesting the probable existence of cryptic species with independent chromosome traits. Therefore, our data can be of great value in discriminating species and understanding their chromosomal evolution.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:26:27Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:42:13Z : No. of bitstreams: 1 2-s2.0-84859169365.pdf: 2551591 bytes, checksum: a386cc8e20c36820fa37034ae15df718 (MD5) Made available in DSpace on 2014-05-27T11:26:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-04-04 Cytogenetic analyses were performed in four species of the Hypostominae subfamily, three from Hypostomus (Hypostomini) genus and Rhinelepis aspera (Rhinelepini). Three populations of Hypostomus ancistroides were analyzed, which had 2n=68 chromosomes, but presented different karyotype formulas. Hypostomus regani and H. strigaticeps, both from Ivaí river, showed 2n=72 chromosomes with two distinct cytotypes. In turn, R. aspera of the upper Paraná river basin presented 2n=54 chromosome. Multiple Nucleolar Organizer Regions (NORs) have been evidenced by silver nitrate staining in species of Hypostomus and single NOR in R. aspera. The observed variation in the chromosome number and the marked variability in karyotype formulas and NORs reveal a certain amount of karyotype variation in the genus Hypostomus suggesting the probable existence of cryptic species with independent chromosome traits. Therefore, our data can be of great value in discriminating species and understanding their chromosomal evolution. Departamento de Biologia Centro de Ciências Biológicas Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900, Maringá, Paraná Departamento de Morfologia Instituto de Biociências Universidade Estadual Paulista Júlio de Mesquita Filho, Botucatu, São Paulo Departamento de Morfologia Instituto de Biociências Universidade Estadual Paulista Júlio de Mesquita Filho, Botucatu, São Paulo