title: First description of B chromosomes in the family Auchenipteridae, Parauchenipterus galeatus (Siluriformes) of the São Francisco River basin (MG, Brazil).
abstract: B chromosomes are considered additional and non-essential; they likely originate from A chromosomes and follow a distinct evolution. In fish, approximately half of the Neotropical species with B chromosomes are Characiformes and 35% are Siluriformes. There has been no report of B chromosomes in Auchenipteridae until this moment. B chromosomes found in a population of Parauchenipterus galeatus from the São Francisco River basin in the state of Minas Gerais (Brazil) were small, metacentric, totally heterochromatic and exhibited intra-individual and inter-individual variation. The diploid number was 58 chromosomes (22 metacentric, 16 submetacentric, 12 subtelocentric and 8 acrocentric). The nucleolar organizing regions were simple and the heterochromatin intercalated in the ribosomal sites, characterized by CMA(3) and DAPI fluorochromes, was of a GC-rich constitution. The 5S rDNA genes were located in an intercalary position in only one chromosome pair. An hypothesis about the origin of the B chromosomes in P. galeatus and a review on B chromosomes in catfish are also presented in this study.
authors.affiliation: Departamento de Genética e Evolução, Universidade Federal de São Carlos, Rodovia Washington Luís (SP 310) Km 235, CEP: 13565-905, São Carlos, SP, Brazil.
authors.forename: Roberto Laridondo
authors.initials: RL
authors.lastname: Lui
authors.forename: Daniel Rodrigues
authors.initials: DR
authors.lastname: Blanco
authors.forename: Vladimir Pavan
authors.initials: VP
authors.lastname: Margarido
authors.forename: Orlando Moreira
authors.initials: OM
authors.lastname: Filho
mesh_terms: D000818:Animals; D001938:Brazil; D002397:Catfishes / Q000235:genetics*; D002875:Chromosomes / Q000648:ultrastructure*; D004171:Diploidy; D009697:Nucleolus Organizer Region; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D045483:Rivers
chemical_list: D012341:RNA, Ribosomal, 5S