title: Cytogenetic analysis in the neotropical fish Astyanax goyacensis Eigenmann, 1908 (Characidae, incertae sedis): karyotype description and occurrence of B microchromosomes.
abstract: BACKGROUND
  B chromosomes, also known as supernumerary or accessory chromosomes, are additional chromosomes over the standard complement found in various groups of plants and animals. We investigated the presence of, and characterized, supernumerary microchromosomes in Astyanax goyacensis using classical and molecular cytogenetic methods.
  
  
  RESULTS
  Three specimens possessed 2n = 50 chromosomes (8m + 26sm + 8st + 8a), and two specimens contained 1 to 9 additional B microchromosomes varying intra- and inter-individually. Chromosome painting with a B chromosome-specific probe yielded signals for several B microchromosomes, with one exhibiting no markings. Acrocentric chromosomes of the standard complement were also painted. Fluorescence in situ hybridization (FISH) using ribosomal probes located two chromosome pairs carrying 18S rDNA marked on the short arm, and one pair carrying 5S rDNA with pericentromeric markings. One chromosome was observed in synteny with 18S cistrons.
  
  
  CONCLUSIONS
  These data contribute to knowledge of the karyotype evolution, the origin of B chromosomes, and to an understanding of the functionality of rDNA.
authors.affiliation: Instituto de Genética e Bioquímica, Universidade Federal de Uberlândia, Av, Pará, 1720, 38400-902 Uberlândia, MG, Brazil. luanabio3@gmail.com.
authors.forename: Luana Pereira
authors.initials: LP
authors.lastname: Dos Santos
authors.forename: Jonathan Pena
authors.initials: JP
authors.lastname: Castro
authors.forename: Carine Mendonça
authors.initials: CM
authors.lastname: Francisco
authors.forename: Marcelo Ricardo
authors.initials: MR
authors.lastname: Vicari
authors.forename: Mara Cristina
authors.initials: MC
authors.lastname: de Almeida
authors.forename: Leonardo Gusso
authors.initials: LG
authors.lastname: Goll
authors.forename: Sandra
authors.initials: S
authors.lastname: Morelli
authors.forename: Roberto Ferreira
authors.initials: RF
authors.lastname: Artoni