title: Sequential steps of chromosomal differentiation in Atlantic surgeonfishes: evolutionary inferences.
abstract: Surgeonfishes are a species-rich group and a major biomass on coral reefs. Three species are commonly found throughout South Atlantic, Acanthurus bahianus, A. chirurgus, and A. coeruleus. In this paper, we present the first cytogenetic data of these species, revealing a sequential chromosomal diversification. A. coeruleus was characterized by a relatively conserved karyotype evolved by pericentric inversions of some pairs (2n = 48, 2sm + 4st + 42a). In contrast, the karyotypes of A. bahianus (2n = 36) and A. chirurgus (2n = 34) were highly differentiated by the presence of six large metacentric pairs in A. bahianus (12m + 2sm + 4st + 18a) and A. chirurgus (12m + 2sm + 4st +1 6a) probably derived by chromosomal fusions that corroborate their closer relationship. A discernible in tandem fusion represents an autapomorphic character to A. chirurgus. In spite of macrostructure variation, single nucleolar organizer regions (NORs) on short arms of a subtelocentric pair and similar distribution of C-bands were observed in the three species. Overlapping of chromosomal data with molecular phylogeny indicated pericentric inversions which took place nearly at 19 Ma while centric fusions are as recent as 5 Ma. A physical mapping of coding and noncoding sequences in Acanthurus could clarify the role of additional rearrangements during their chromosomal evolution.
authors.affiliation: Departamento de Ciências Biológicas, Universidade Estadual do Sudoeste da Bahia, 45206-150 Jequié, BA, Brazil.
authors.forename: Paulo Roberto Antunes de Mello
authors.initials: PR
authors.lastname: Affonso
authors.affiliation: Departamento de Biologica Celular e Genética, Universidade Federal do Rio Grande do Norte, 59078-970 Natal, RN, Brazil.
authors.forename: Maria Aparecida
authors.initials: MA
authors.lastname: Fernandes
authors.affiliation: Departamento de Ciências Biológicas, Universidade Estadual do Sudoeste da Bahia, 45206-150 Jequié, BA, Brazil.
authors.forename: Josivanda Santos
authors.initials: JS
authors.lastname: Almeida
authors.affiliation: Departamento de Biologica Celular e Genética, Universidade Federal do Rio Grande do Norte, 59078-970 Natal, RN, Brazil.
authors.forename: Wagner Franco
authors.initials: WF
authors.lastname: Molina
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D001938:Brazil; D002875:Chromosomes / Q000235:genetics*; D020732:Cytogenetic Analysis; D019143:Evolution, Molecular; D009697:Nucleolus Organizer Region / Q000235:genetics; D010473:Perciformes / Q000235:genetics*; D010802:Phylogeny; D013045:Species Specificity