title: Chromosomal diversity in Hypostomus (Siluriformes,  Loricariidae) with emphasis on physical mapping of 18S and 5S rDNA sites.
abstract: We examined chromosomes of three species of the genus Hypostomus,  in order to contribute to the understanding of the karyotype evolution of this  group. Specimens of H. ancistroides and H. nigromaculatus displayed  differences in karyotype formulas, distribution and location of heterochromatin  and nucleolus organizer regions when compared to other populations of the same  species. We made the first cytogenetic characterization of H. tapijara,  an endemic species in the Ribeira de Iguape River. These specimens had 2n = 66  chromosomes, while H. ancistroides showed 2n = 68 and H.  nigromaculatus 2n = 76 chromosomes. Physical mapping of 18S and 5S rDNA  sites of the three species showed simple, multiple and syntenic clusters.  Synteny of ribosomal sites was found in H. ancistroides and H.  tapijara, and an interspersed pattern between these sites in all  chromosomes bearing the synteny was observed. We conclude that the genus Hypostomus has a high chromosome complexity that is accompanied by great morphological  variation. It is evident that this group comprises an interesting model for  understanding the chromosome evolution of Neotropical ichthyofauna.
authors: Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brasil. jositraldi@hotmail.com
authors: J B
authors: JB
authors: Traldi
authors: D R
authors: DR
authors: Blanco
authors: M R
authors: MR
authors: Vicari
authors: J F
authors: JF
authors: Martinez
authors: R L
authors: RL
authors: Lui
authors: A V
authors: AV
authors: Barros
authors: R F
authors: RF
authors: Artoni
authors: O
authors: O
authors: Moreira-Filho
mesh_terms: D000818:Animals; D002397:Catfishes / Q000235:genetics*; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics*; D003582:Cytogenetics / Q000379:methods; D004275:DNA, Ribosomal / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D014644:Genetic Variation; D006570:Heterochromatin / Q000235:genetics; D007621:Karyotyping / Q000379:methods; D008297:Male; D009697:Nucleolus Organizer Region / Q000235:genetics
chemical_list: D004275:DNA, Ribosomal; D006570:Heterochromatin