Volumen 41 - Número 1: 57-62 | 2006
Article

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Cytogenetic characterization of the silverside fish Odontesthes regia (Humboldt, 1833) (Teleostei: Atheriniformes: Atherinopsidae) from Iquique, Chile

Carlos Muñoz¹, Mauro Nirchio²*, Julio E. Pérez³, Ernesto Ron² Claudio Oliveira⁴ and Irani A. Ferreira⁴

¹Departamento de Ciencias del Mar, Universidad Arturo Prat, Iquique, Chile, Casilla Nº 121
²Escuela de Ciencias Aplicadas del Mar, Universidad de Oriente, Isla de Margarita, Venezuela, Apartado Postal 147
³Instituto Oceanográfico de Venezuela, Universidad de Oriente, Cumaná, Venezuela
⁴Departamento de Morfologia, Instituto de Biociências, Universidade Estadual Paulista, 18618-000 Botucatu, São Paulo, Brazil

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This paper describes the karyotype of Odontesthes regia by means of Giemsa staining, C-banding, to reveal the distribution of the constitutive heterochromatin, and by Ag-staining and fluorescent in situ hybridization (FISH), to locate ribosomal genes (rDNA). The chromosome diploid modal count in the species was 2n = 48. The karyotype is composed of one submetacentric pair (pair 1), 16 subtelocentric pairs (pairs 2 to 17), and 7 acrocentric pairs (pairs 18 to 24). With the exception of pair 1 it was not possible to classify the homologous chromosomes accurately because differences in chromosome size were too slight between adjacent pairs. The distribution of C-banded heterochromatin allowed for a more accurate matching of the majority of chromosomes of the subtelocentric series. Silver staining of metaphase spreads allowed for the identification of Nucleolus Organizer Regions (Ag-NOR) on pair 1. FISH experiments showed that 18S rDNA sequences were located, as expected, in the same chromosome pair identified as the Ag-NOR-bearing one.

Key words: Karyotype, NOR, C-bands, FISH