title: Polymorphisms of the nucleolus organizing regions in Loricaria cataphracta (Siluriformes, Loricariidae) of the upper Paraguay River basin indicate an association with transposable elements.
abstract: A cytogenetic analysis of Loricaria cataphracta revealed a diploid number of 2n = 64 chromosomes, distributed as 12 metacentric + 8 submetacentric + 2 subtelocentric + 42 acrocentric, with a fundamental number of 86. Analysis of the nucleolus organizing region (NOR) using silver nitrate impregnation and fluorescence in situ hybridization (18S rDNA probe) techniques showed intra-population chromosomal polymorphism that could be classified into five different patterns (I to V), involving four pairs of chromosomes (8, 9, 12, and 13). In pattern I, the NOR was located in pair 12, whereas in pattern II, the NOR was detected in pair 8; these two patterns were characterized as a simple-NOR system. A multiple NOR system was evident in the other patterns (III, IV, and V). In pattern III, the NOR was located in only one of the homologs of pairs 12 and 8, and in patterns IV and V, the NOR was observed in pair 12 and in only one of the homologs of pairs 9 and 13, respectively. In addition, C-band analysis also showed this pattern of variation, and characterized a polymorphism in relation to the constitutive heterochromatin; the composition of this region was GC-rich (positive CMA3) and 4',6-diamidino-2-phenylindole negative. Transposition of NOR sites for mobile elements is suggested to explain this polymorphism.
authors.affiliation: Departamento de Biotecnologia, Genética e Biologia Celular, Universidade Estadual de Maringá, Maringá, PR, Brasil ferreroporto@yahoo.com.br.
authors.forename: F E
authors.initials: FE
authors.lastname: Porto
authors.affiliation: Universidade Estadual de Mato Grosso do Sul, Unidade Universitária de Coxim, Coxim, MS, Brasil.
authors.forename: B S
authors.initials: BS
authors.lastname: Gindri
authors.affiliation: Universidade Estadual de Mato Grosso do Sul, Unidade Universitária de Coxim, Coxim, MS, Brasil.
authors.forename: M M R
authors.initials: MM
authors.lastname: Vieira
authors.affiliation: Departamento de Biotecnologia, Genética e Biologia Celular, Universidade Estadual de Maringá, Maringá, PR, Brasil.
authors.forename: L A
authors.initials: LA
authors.lastname: Borin
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; D004251:DNA Transposable Elements / Q000235:genetics*; D007915:Lepidoptera / Q000235:genetics*; D009697:Nucleolus Organizer Region / Q000235:genetics*; D010239:Paraguay; D011110:Polymorphism, Genetic; D045483:Rivers
chemical_list: D004251:DNA Transposable Elements