Abstract
BackgroundNowadays, the genus Bryconamericus is placed in subfamily Stevardiinae within of Characidae, but not shows consistent evidence of monophyletism. The purpose of this work was to study the chromosomes of three species of Bryconamericus, aiming to add cytogenetic knowledge and contribute to the understanding of the chromosomal evolution of this genus.ResultsThe chromosomes of three species of Bryconamericus were analyzed using cytogenetic techniques. The karyotype of Bryconamericus stramineus contained 6 metacentric (m) + 10 submetacentric (sm) + 16 subtelocentric (st) + 20 acrocentric (a), the fundamental number (FN) of 84, one silver impregnated (Ag-NOR) pair, one pair bearing the 18S ribosomal DNA sites, another pair bearing the 5S rDNA sites, and a few positive C-bands. Bryconamericus turiuba had a karyotype containing 8 m + 10sm + 14st + 20a (FN = 84), one chromosome pair Ag-NOR, two pairs bearing the 18S rDNA sites, two pairs bearing the 5S rDNA sites, and a few C-band regions. Bryconamericus cf. iheringii had a karyotype containing 10 m + 14sm + 18st + 10a (FN = 94), including one pair with a secondary constriction Ag-NOR positive. In this karyotype the fluorescent in situ hybridization (FISH) showed the 18S and 5S rDNA probe in adjacent position.ConclusionsThe results obtained in this work showed different characteristics in the organization of two multigene families, indicating that distinct evolutionary forces acting on the diversity of rDNA sequences in the genome of three Bryconamericus species.
Highlights
Nowadays, the genus Bryconamericus is placed in subfamily Stevardiinae within of Characidae, but not shows consistent evidence of monophyletism
The double-fluorescent in situ hybridization (FISH) technique was used to confirm that the two Ribosomal DNA (rDNA) (18S and 5S) clusters were physically located in different chromosome pairs (Figure 3D)
The karyotypes of B. stramineus and B. turiuba were similar in terms of their acrocentric chromosome number and they shared the same fundamental number (FN) (84)
Summary
The genus Bryconamericus is placed in subfamily Stevardiinae within of Characidae, but not shows consistent evidence of monophyletism. According to the published data there are about 70 species described in the genus Bryconamericus [1]. New species have been described, including a species from French Guyana known as Bryconamericus guyanensis sp. According to Géry [3] the genus Bryconamericus belonged to the subfamily Tetragonopterinae. The Bryconamericus species were included in Characidae incertae sedis by Lima et al [4]. More recently Mirande [5] and Oliveira et al [6] showed that Bryconamericus can be a polyphyletic group, but included within of the subfamily Stevardiinae (Family Characidae) and no more in incertae sedis as proposed by Lima et al [4]
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