title: Karyotype structure of Hypostomus cf. plecostomus (Linnaeus, 1758) from Tapajós River basin, Southern Amazon: occurrence of sex chromosomes (ZZ/ZW) and their evolutionary implications.
abstract: Hypostomus is a group of fish with numerical and struc-tural karyotypic variability. Among them, only six species, three of which belong to the Amazon basin, show a sex chromosome. In this study, we present the karyotype structure of Hypostomus cf. plecos-tomus from the Teles Pires river basin in the municipality of Alta Flo-resta, MT. The species has 2n = 68 and the karyotype formula 14m+ 24sm+ 14st+ 16a [fundamental number (FN) = 120] in males and 15m+ 24sm+14st+15a (FN = 121) in females and sex chromosomes ZZ/ZW. Argyrophilic nucleolar organizer regions (AgNORs) were identified in two pairs of chromosomes at different positions: short arm of the pair 21and long arm of the pair 27, matching the signals displayed by 18S FISH and indicating multiple NORs. Analysis of band C detected few blocks of constitutive heterochromatin in the pericentromeric regions of most chromosomes and the telomeric regions of some pairs, includ-ing the nucleolar pair 21. However, large blocks on the long arm of the nucleolar pair 27 still stood out. GC-rich heterochromatin (CMA3) was visualized only coincidently with nucleolar sites. Mapping of 5S rDNA sites with FISH revealed markings in eight chromosomes, demonstrat-ing synteny between the 18S and 5S sites. The data obtained for H. cf. plecostomus are important for taxonomic studies of this Amazon com-plex "H. plecostomus group". The occurrence of sex chromosomes in Amazon species of Hypostomus suggests an evolutionary event that is independent of other species in the group.
authors.affiliation: Departamento de Ciências Biológicas, Universidade do Estado de Mato Grosso, Alta Floresta, MT, Brasil lucienecastuera@hotmail.com.
authors.forename: L C
authors.initials: LC
authors.lastname: Oliveira
authors.affiliation: Departamento de Ciências Biológicas, Universidade Estadual do Paraná, União da Vitória, PR, Brasil.
authors.forename: M O
authors.initials: MO
authors.lastname: Ribeiro
authors.affiliation: Departamento de Ciências Biológicas, Universidade do Estado de Mato Grosso, Nova Xavantina, MT, Brasil.
authors.forename: E S
authors.initials: ES
authors.lastname: Dutra
authors.affiliation: Departamento de Biologia, Nupélia, Universidade Estadual de Maringá, Maringá, PR, Brasil.
authors.forename: C H
authors.initials: CH
authors.lastname: Zawadzki
authors.affiliation: Departamento de Biotecnologia, Genética e Biologia Celular, Universidade Estadual de Maringá, Maringá, PR, Brasil.
authors.forename: A L B
authors.initials: AL
authors.lastname: Portela-Castro
authors.affiliation: Departamento de Biotecnologia, Genética e Biologia Celular, Universidade Estadual de Maringá, Maringá, PR, Brasil.
authors.forename: I C
authors.initials: IC
authors.lastname: Martins-Santos
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002397:Catfishes / Q000235:genetics*; D002871:Chromosome Banding; D005260:Female; D017404:In Situ Hybridization, Fluorescence; D059785:Karyotype; D008297:Male; D045483:Rivers; D012730:Sex Chromosomes / Q000235:genetics*