title: Co-located 18S/5S rDNA arrays: an ancient and unusual chromosomal trait in Julidini species (Labridae, Perciformes).
abstract: Wrasses (Labridae) are extremely diversified marine fishes, whose species exhibit complex interactions with the reef environment. They are widely distributed in the Indian, Pacific and Atlantic oceans. Their species have displayed a number of karyotypic divergent processes, including chromosomal regions with complex structural organization. Current cytogenetic information for this family is phylogenetically and geographically limited and mainly based on conventional cytogenetic techniques. Here, the distribution patterns of heterochromatin, GC-specific chromosome regions and Ag-NORs, and the organization of 18S and 5S rDNA sites of the Atlantic speciesThalassoma noronhanum(Boulenger, 1890),Halichoeres poeyi(Steindachner, 1867),Halichoeres radiatus(Linnaeus, 1758),Halichoeres brasiliensis(Bloch, 1791) andHalichoeres penroseiStarks, 1913, belonging to the tribe Julidini were analyzed. All the species exhibited 2n=48 chromosomes with variation in the number of chromosome arms among genera.Thalassoma noronhanumhas 2m+46a, while species of the genusHalichoeresRüppell, 1835 share karyotypes with 48 acrocentric chromosomes. TheHalichoeresspecies exhibit differences in the heterochromatin distribution patterns and in the number and distribution of 18S and 5S rDNA sites. The occurrence of 18S/5S rDNA syntenic arrangements in all the species indicates a functionally stable and adaptive genomic organization. The phylogenetic sharing of this rDNA organization highlights a marked and unusual chromosomal singularity inside the family Labridae.
authors.affiliation: Departamento de Biologia Celular e Genética, Centro de Biociências, Universidade Federal do Rio Grande do Norte, Campus Universitário, Lagoa Nova, 3000, 59078-970, Natal, RN, Brasil.
authors.forename: Karlla Danielle Jorge
authors.initials: KD
authors.lastname: Amorim
authors.affiliation: Departamento de Genética e Evolução, Universidade Federal de São Carlos, Rodovia Washington Luís, km 235,13565-905, São Carlos, SP, Brasil.
authors.forename: Marcelo de Bello
authors.initials: MB
authors.lastname: Cioffi
authors.affiliation: Departamento de Genética e Evolução, Universidade Federal de São Carlos, Rodovia Washington Luís, km 235,13565-905, São Carlos, SP, Brasil.
authors.forename: Luiz Antonio Carlos
authors.initials: LA
authors.lastname: Bertollo
authors.affiliation: Departamento de Biologia Celular e Genética, Centro de Biociências, Universidade Federal do Rio Grande do Norte, Campus Universitário, Lagoa Nova, 3000, 59078-970, Natal, RN, Brasil.
authors.forename: Rodrigo Xavier
authors.initials: RX
authors.lastname: Soares
authors.affiliation: Departamento de Biologia Celular e Genética, Centro de Biociências, Universidade Federal do Rio Grande do Norte, Campus Universitário, Lagoa Nova, 3000, 59078-970, Natal, RN, Brasil.
authors.forename: Allyson Santos
authors.initials: AS
authors.lastname: de Souza
authors.affiliation: Departamento de Biologia Celular e Genética, Centro de Biociências, Universidade Federal do Rio Grande do Norte, Campus Universitário, Lagoa Nova, 3000, 59078-970, Natal, RN, Brasil.
authors.forename: Gideão Wagner Werneck Felix
authors.initials: GW
authors.lastname: da Costa
authors.affiliation: Departamento de Biologia Celular e Genética, Centro de Biociências, Universidade Federal do Rio Grande do Norte, Campus Universitário, Lagoa Nova, 3000, 59078-970, Natal, RN, Brasil.
authors.forename: Wagner Franco
authors.initials: WF
authors.lastname: Molina
keywords: Chromosome evolution; Halichoeres; rDNA; syntenic genes; wrasses