title: Possible origins of B chromosomes in Rineloricaria pentamaculata (Loricariidae, Siluriformes) from the Paraná River basin.
abstract: We made a cytogenetic study of Rineloricaria pentamaculata from the Tauá Stream, in the Pirapó River sub-basin in Paraná State, Brazil, focused on the occurrence and origins of the B chromosomes. The diploid number varied from 2n = 56 to 2n = 59, due to the presence of 0 to 3 B microchromosomes of the acrocentric type, which were observed in 92.3% of the specimens (N = 12). These chromosomes were totally heterochromatic, with the C banding technique, and there were inter- and intraindividual numerical differences. Meiotic cells in metaphase I had 28 bivalent chromosomes and 0 to 3 univalent chromosomes. We suggest that the B microchromosomes are centric fragments originated from chromosome rearrangements.
authors.affiliation: Departamento de Biologia Celular e Genética, Universidade Estadual de Maringá, Maringá, PR, Brasil. ferreroporto@yahoo.com.br
authors.forename: F E
authors.initials: FE
authors.lastname: Porto
authors.forename: A L B
authors.initials: AL
authors.lastname: Portela-Castro
authors.forename: I C
authors.initials: IC
authors.lastname: Martins-Santos
mesh_terms: D000818:Animals; D002397:Catfishes / Q000235:genetics*; D002875:Chromosomes / Q000235:genetics*; D006570:Heterochromatin / Q000235:genetics
chemical_list: D006570:Heterochromatin