title: Karyotypic variability in Iheringichthys labrosus (Teleostei, Pimelodidae) from the Tibagi River basin (Paraná State, Brazil).
abstract: Cytogenetic analyses were carried out in a populational sample of Iheringichthys labrosus from the Guaraúna River (Upper Tibagi River; Paraná State, Brazil) in order to provide a karyotypic comparison with another previously studied population from the Lower Tibagi River, characterized by the presence of 32m + 8sm + 6st + 10a (2n = 56, FN = 102) and occurrence of supernumerary chromosomes (80% of individuals). The 17 specimens of I. labrosus (6 females, 10 males and 1 of unknown sex) from the Upper Tibagi River showed 2n = 56 chromosomes, a karyotype formula of 14m + 32sm + 4st + 6a (FN = 106), without evidence of sex chromosome heteromorphism or supernumerary chromosomes. The heterochromatin was detected at telomeric and centromeric positions in several chromosomal pairs. The Ag-nucleolar organizer regions were heteromorphic and located at terminal position on short arms of the 16th chromosomal pair, suggesting a positive association with heterochromatic regions. The inter-populational karyotypic differentiation reported indicates distinct evolutionary pathways within I. labrosus in the Tibagi River basin.
authors.affiliation: Programa de Pós-Graduação em Genética, Conservação e Biologia Evolutiva, Instituto Nacional de Pesquisas da Amazônia, Manaus, AM, Brasil.
authors.forename: L B
authors.initials: LB
authors.lastname: Ribeiro
authors.forename: D A
authors.initials: DA
authors.lastname: Matoso
authors.forename: M C
authors.initials: MC
authors.lastname: Almeida
authors.forename: M R
authors.initials: MR
authors.lastname: Vicari
authors.forename: A
authors.initials: A
authors.lastname: Moraes-Neto
authors.forename: M C C M
authors.initials: MC
authors.lastname: Svidnicki
authors.forename: R F
authors.initials: RF
authors.lastname: Artoni