Conserved Cytogenetic Features in the Amazonian Arapaima, Arapaima gigas (Schinz 1822) from Jamari River, Rondônia–Brazil

Renata da Rosa1, Marceléia Rubert2, Mauro Caetano-Filho3, Lucia Giuliano-Caetano*, 4
1 Departamento de Biologia Celular e Genética, Universidade Estadual de Maringá, CEP 87020-900, Caixa Postal 331, Maringá, Paraná, Brazil
2 Departamento de Genética e Evolução, Universidade Federal de São Carlos, CEP 13565-905, Caixa Postal 676, São Carlos, São Paulo, Brazil
3 Departamento de Biologia Animal e Vegetal, CCB, Universidade Estadual de Londrina. CEP 86051-990, Caixa Postal 6001, Londrina, Paraná, Brazil
4 Departamento de Biologia Geral, CCB, Universidade Estadual de Londrina. CEP 86051-990, Caixa Postal 6001, Londrina, Paraná, Brazil

© 2009 da Rosa et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* 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:


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.