title: Nucleolar organizing regions, 18S and 5S rDNA in Astyanax scabripinnis (Pisces, Characidae): populations distribution and functional diversity.
abstract: Astyanax scabripinnis specimens from four distinct populations in Brazil were studied with respect to their karyotype macrostructure, nucleolar organizer regions, and 18S and 5S rRNA genes. The four populations showed a 2n = 50 chromosomes (3 M + 11 SM + 5 ST + 6 A pairs) and 1-2 B chromosomes. No chromosomal differentiations were observed between sexes. Although a karyotypic diversity has been characterized in this fish group, the populations now analyzed presented the same macrokaryotypic pattern. Chromosome mapping of 5S rDNA showed a total of eight sites located in four distinct chromosomal pairs, with no apparent differences among populations. A comparative study on 18S rDNA locations and Ag-NORs showed some secondary NOR sites that are not usually expressed in karyotypes and a probable differential NOR activity among populations. Correlations between these data, environmental conditions and B chromosomes are discussed.
authors.affiliation: Universidade Federal de São Carlos, Departamento de Genética e Evolução, SP, Brazil.
authors.forename: D A
authors.initials: DA
authors.lastname: Ferro
authors.forename: D M
authors.initials: DM
authors.lastname: Néo
authors.forename: O
authors.initials: O
authors.lastname: Moreira-Filho
authors.forename: L A
authors.initials: LA
authors.lastname: Bertollo
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D004275:DNA, Ribosomal / Q000235:genetics*; D005399:Fishes / Q000235:genetics*; D007621:Karyotyping; D009697:Nucleolus Organizer Region; D012337:RNA, Ribosomal, 18S / Q000235:genetics*; D012341:RNA, Ribosomal, 5S / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D012341:RNA, Ribosomal, 5S