TOBIOJ The Open Biology Journal Open Bio. J. 1874-1967 Bentham Open TOBIOJ-2-91 10.2174/1874196700902010091 Biology Conserved Cytogenetic Features in the Amazonian Arapaima, Arapaima gigas (Schinz 1822) from Jamari River, Rondônia–Brazil da Rosa Renata 1 Rubert Marceléia 2 Caetano-Filho Mauro 3 Giuliano-Caetano Lucia * 4 Departamento de Biologia Celular e Genética, Universidade Estadual de Maringá, CEP 87020-900, Caixa Postal 331, Maringá, Paraná, Brazil Departamento de Genética e Evolução, Universidade Federal de São Carlos, CEP 13565-905, Caixa Postal 676, São Carlos, São Paulo, Brazil Departamento de Biologia Animal e Vegetal, CCB, Universidade Estadual de Londrina. CEP 86051-990, Caixa Postal 6001, Londrina, Paraná, Brazil Departamento de Biologia Geral, CCB, Universidade Estadual de Londrina. CEP 86051-990, Caixa Postal 6001, Londrina, Paraná, Brazil Address correspondence to this author at the Departamento de Biologia Geral - CCB - Universidade Estadual de Londrina, P. O. Box 6001 – CEP: 86051-990, Londrina – Paraná – Brazil; Tel: 55 (43)33714417; Fax: 55(43)33714527; E-mail: giuliano@uel.br 31 8 2009 2009 2 91 94 22 11 2008 15 05 2009 05 06 2009 © 2009 da Rosa et al. 2009 Renata da Rosa

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Specimens of Arapaima gigas from Jamari River (RO) were cytogenetically analyzed. A diploid number of 2n=56 chromosomes was found (28m-sm + 28st-a). Secondary constrictions were observed on the short arms of chromosome 3. Nucleolar Organizer Regions (NORs) were detected at the subterminal region on short arms of the third chromosomal pair by both silver nitrate staining and FISH with 45S rDNA probe, being equivalent to secondary constrictions. The ribosomal sites were also characterized by size heteromorphism and presence of CMA3+/DAPI- blocks.

The constitutive heterochromatin was located at pericentromeric region of some chromosomes. After sequential Cbanding and base-specific fluorochromes staining, most of the heterochromatins proved to be neutral, i.e., with similar amounts of AT and GC bases. Nonetheless, some heterochromatic regions were marked by GC-specific fluorochromes in one chromosomal pair and by AT-specific fluorochrome staining on two pairs. The present data are in agreement with previous reports in populations from Araguaya River, indicating that conserved cytogenetic features are present in this important fish species.

 Keywords Fish cytogenetics pirarucu chromosomal conservativeness FISH