Chromosomal characterization of the bonytongue Arapaima gigas (Osteoglossiformes: Arapaimidae)

Abstract

The mitotic chromosomes of the pirarucu Arapaima gigas inhabiting the middle Araguaia River and collected in the municipality of Araguaiana (MT, Brazil) were studied. The chromosomes were analyzed through Giemsa staining, C-banding, Ag-NOR staining and in situ hybridization using an 18S rRNA gene probe. The karyotype had 2n=56 comprising 14 biarmed and 14 uniarmed chromosome pairs in both sexes. No cytologically distinguishable sex chromosome was identified. A single NORbearing chromosome pair was detected by Ag-NOR staining and confirmed by 18S rDNA -FISH. Faint constitutive heterochromatin was C-banded in the centromeric region of some chromosomes.Estudamos os cromossomos mitóticos do pirarucu Arapaima gigas, proveniente do médio rio Araguaia, município de Araguaiana (MT, Brasil). As preparações mitóticas foram analisadas através de coloração com Giemsa, bandas-C e nitrato de prata (AgNORs). Também foram realizadas análises através de hibridização in situ utilizando sondas de DNAr 18S. O cariótipo mostrou 2n=56 cromossomos, sendo 14 pares meta-submetacêntricos e 14 subtelo-acrocêntricos. Não foram observadas diferenças cromossômicas associadas ao sexo. Foi detectado apenas um par de cromossomos portador de Ag-NORs. Essa observação foi confirmada pelo FISH do DNAr 18S. Pequenos blocos de heterocromatina foram observados na região centromérica de alguns pares cromossômicos.

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

“…In the specimens of A. gigas from Rondônia, the subterminal secondary constrictions were located on the third chromosomal pair, coincidently to the active single NORs, just like reported in the populations from Araguaya River [19,8]. Indeed, most of the Neotropical fish species present single NORs, such as reported in Curimatidae [20], Parodontidae [21,22], Salminae, and Bryconinae [23], among others.…”

“…The present results showed similar karyotype features with previous reports in A. gigas. A diploid number of 56 chromosomes were also reported in specimens from Araguaya River, Amazon region, by Marques et al [8].…”

“…Marques et al [8] carried out cytogenetic studies in a population of this species collected in Middle Araguaya River, municipality of Araguaiana (MT, Brazil). These authors reported a diploid number of 2n= 56 chromosomes for both males and females, single NORs, and small heterochromatic blocks at the centromeric region.…”

Genetic diversity of Arapaima gigas (Schinz, 1822) (Osteoglossiformes: Arapaimidae) in the Araguaia-Tocantins basin estimated by ISSR marker

“…Several studies about genetic diversity in A. gigas have been carried in the Amazon region, with the purpose of determining the risk of extinction of this species and helping to define appropriate strategies for their management (Farias et al, 2003;Hrbek et al, 2005;Hrbek & Farias, 2008;Hamoy et al, 2008;Araripe et al, 2013). Thus, while there are already several studies concerning the stocks of the Amazonian plain, there is only one study based on chromosomal/ genetic markers in the plain of the rio Araguaia, and this study was conducted at a single location in the middle rio Araguaia (Marques et al, 2006). This study indicated that the samples collected were part of a single population with high intra-population genetic diversity.…”

The monotony of transferrin and esterase electrophoretic patterns in pirarucu, Arapaima gigas (Schinz, 1822) from Santa Cruz Lake, Tefé River, Amazonas, Brazil

“…More recently, there have been other studies on population genetics, based on mitochondrial DNA sequences (Hrbek et al, 2005), gonadal morphology and reproductive traits (Godinho et al, 2005), feeding analyses (Olivera et al, 2005), and mitotic chromosomes (Marques et al, 2006), in wild-fish samples from several sites in the Amazon region. All of these studies without exception have yielded valuable information for the management and conservation policies of this species.…”