title: Chromosomal painting and ZW sex chromosomes differentiation in Characidium (Characiformes, Crenuchidae).
abstract: BACKGROUND
  The Characidium (a Neotropical fish group) have a conserved diploid number (2n = 50), but show remarkable differences among species and populations in relation to sex chromosome systems and location of nucleolus organizer regions (NOR). In this study, we isolated a W-specific probe for the Characidium and characterized six Characidium species/populations using cytogenetic procedures. We analyzed the origin and differentiation of sex and NOR-bearing chromosomes by chromosome painting in populations of Characidium to reveal their evolution, phylogeny, and biogeography.
  
  
  RESULTS
  A W-specific probe for efficient chromosome painting was isolated by microdissection and degenerate oligonucleotide primed-polymerase chain reaction (DOP-PCR) amplification of W chromosomes from C. gomesi. The W probe generated weak signals dispersed on the proto sex chromosomes in C. zebra, dispersed signals in both W and Z chromosomes in C. lauroi and, in C. gomesi populations revealed a proximal site on the long arms of the Z chromosome and the entire W chromosome. All populations showed small terminal W probe sites in some autosomes. The 18S rDNA revealed distinctive patterns for each analyzed species/population with regard to proto sex chromosome, sex chromosome pair, and autosome location.
  
  
  CONCLUSIONS
  The results from dual-color fluorescence in situ hybridization (dual-color FISH) using W and 18S rDNA probes allowed us to infer the putative evolutionary pathways for the differentiation of sex chromosomes and NORs, from structural rearrangements in a sex proto-chromosome, followed by gene erosion and heterochromatin amplification, morphological differentiation of the sex chromosomal pair, and NOR transposition, giving rise to the distinctive patterns observed among species/populations of Characidium. Biogeographic isolation and differentiation of sex chromosomes seem to have played a major role in the speciation process in this group of fish.
authors.affiliation: Departamento de Biologia Estrutural, Molecular e Genética, Universidade Estadual de Ponta Grossa, Av. Carlos Cavalcanti, 4748, Ponta Grossa-PR, 84030-900, Brazil.
authors.forename: Tatiana C
authors.initials: TC
authors.lastname: Machado
authors.forename: José C
authors.initials: JC
authors.lastname: Pansonato-Alves
authors.forename: Marcela B
authors.initials: MB
authors.lastname: Pucci
authors.forename: Viviane
authors.initials: V
authors.lastname: Nogaroto
authors.forename: Mara C
authors.initials: MC
authors.lastname: Almeida
authors.forename: Claudio
authors.initials: C
authors.lastname: Oliveira
authors.forename: Fausto
authors.initials: F
authors.lastname: Foresti
authors.forename: Luiz A C
authors.initials: LA
authors.lastname: Bertollo
authors.forename: Orlando
authors.initials: O
authors.lastname: Moreira-Filho
authors.forename: Roberto F
authors.initials: RF
authors.lastname: Artoni
authors.forename: Marcelo R
authors.initials: MR
authors.lastname: Vicari
mesh_terms: D000818:Animals; D005075:Biological Evolution; D020223:Chromosome Painting; D005260:Female; D005399:Fishes / Q000235:genetics*; D007621:Karyotyping; D010802:Phylogeny; D012730:Sex Chromosomes; D012733:Sex Differentiation