Cytogenetic variation of repetitive DNA elements in Hoplias malabaricus (Characiformes - Erythrinidae) from white, black and clear water rivers of the Amazon basin

Abstract Hoplias malabaricus is a common fish species occurring in white, black and clear water rivers of the Amazon basin. Its large distribution across distinct aquatic environments can pose stressful conditions for dispersal and creates possibilities for the emergence of local adaptive profiles. We investigated the chromosomal localization of repetitive DNA markers (constitutive heterochromatin, rDNA and the transposable element REX-3) in populations from the Amazonas river (white water), the Negro river (black water) and the Tapajós river (clear water), in order to address the variation/association of cytogenomic features and environmental conditions. We found a conserved karyotypic macrostructure with a diploid number of 40 chromosomes (20 metacentrics + 20 submetacentrics) in all the samples. Heteromorphism in pair 14 was detected as evidence for the initial differentiation of an XX/XY system. Minor differences detected in the amount of repetitive DNA markers are interpreted as possible signatures of local adaptations to distinct aquatic environments

Chromosomal population structuring in carangids (Perciformes) between the north-eastern and south-eastern coasts of Brazil

The family Carangidae comprises 151 species, of which only 19 have been so far karyotyped, including a few representatives from the Western Atlantic Ocean. This study compared the cytogenetic features of three Atlantic carangids, Chloroscombrus chrysurus, Trachinotus goodei and T. falcatus, from north-eastern Brazilian coast, with previously obtained cytogenetic data from southern populations. All species presented 2n = 48 chromosomes. Chloroscombrus chrysurus showed a conserved karyotypic macrostructure (2n = 48a, FN = 48) whereas T. goodei (2m + 2sm + 44a; FN = 52) and T. falcatus (2n = 10m/sm + 38a; FN = 58) presented more diversified karyotypes. Data showed that the samples of C. chrysurus from the north-eastern and south-eastern regions did not differ cytogenetically. However, the frequency or position of ribosomal sites (Ag-NOR/18S rDNA) were effective in discriminating the populations of Trachinotus between these coastal regions. The distinct chromosomal patterns suggest a historical genetic fractionating of the Trachinotus populations along the Brazilian coast.Keywords: Chloroscombrus chrysurus, fish cytogenetics, population structure, ribosomal sites, Trachinotus falcatus, Trachinotus goodeiAfrican Journal of Marine Science 2012, 34(3): 383–38

Cytogenetic and Molecular Data Demonstrate that the Bryconinae (Ostariophysi, Bryconidae) Species from Southeastern Brazil Form a Phylogenetic and Phylogeographic Unit

<div><p><i>Brycon</i> spp. occur in Neotropical watersheds to the west and east of the Andes, and as they are sensitive to anthropogenic changes, many these species are endangered in southeastern Brazil. Coastal rivers in southeastern Brazil are characterized by the presence of relatively few freshwater fish species and high endemism of this fauna. The objective of this study was to examine whether <i>Brycon</i> spp. occurring in the coastal basins of southeastern Brazil are monophyletic, using cytogenetic data, mitochondrial, and nuclear molecular markers. All the species showed a diploid number of 50 chromosomes, a conserved number within the subfamily Bryconinae. However, the karyotypic formulas were unique to most species, including <i>Brycon devillei</i> (26m+22sm+2st), <i>Brycon ferox</i> (26m+12sm+12st), <i>Brycon insignis</i> (22m+20sm+8st), <i>Brycon opalinus</i>, and <i>Brycon vermelha</i> (24m+20sm+6st), indicating the prevalence of pericentric and paracentric inversions in the chromosomal evolution of these species. All of them had nucleolar organizer regions in the first pair of subtelocentric chromosomes and no equilocal distribution of heterochromatin in the first pair of chromosomes of the karyotype. These two features, not seen in any other <i>Brycon</i> spp. examined to date, indicate that Bryconinae species from the Brazilian southeastern coastal basins, including the monotypic genus <i>Henochilus</i>, are monophyletic. Also, this is the first study that reports NOR location and C-banding patterns as synapomorphies for a Neotropical fish species group. The monophyly was also supported by a phylogenetic analysis of <i>16S</i> rDNA (<i>16S</i>), cytochrome oxidase subunit I (<i>COI</i>), alpha-myosin (<i>MYH6</i>) genes and <i>S72</i> intron molecular data. Our results partially corroborate the “<i>Brycon acuminatus</i>” group proposed by Howes in 1982: our proposed clade keeps <i>B</i>. <i>devillei</i>, <i>B</i>. <i>ferox</i>, and <i>B</i>. <i>insignis;</i> but it also includes <i>B</i>. <i>opalinus</i>, <i>B</i>. <i>vermelha</i>, and <i>H</i>. <i>weatlandii</i> whereas it excludes <i>B</i>. <i>nattereri</i>. The phylogeographic unit formed by Bryconinae species in southeastern Brazil reflects the long and isolated paleohydrological history of these coastal basins relative to the continental watersheds.</p></div