Luana Pereira Dos Santos, Carine M Francisco, Edimar O Campos Júnior, Jonathan P Castro, Ricardo Utsunomia, Sandra Morelli, Fábio Porto-Foresti, Fausto Foresti, Roberto F Artoni
Cytogenetic and genome research 2021B chromosomes occur in different species of the small characid fishes of the genus Moenkhausia. These supernumerary elements, that do not recombine with chromosomes of the standard A complement and follow their own evolutionary mechanism vary in number, morphology, and distribution. Here, we show karyotypic data of individuals of 2 populations of Moenkhausia oligolepis of the Brazilian Amazon (Pedro Correia and Taboquinha streams, Tocantins river basin), both with a diploid number of 50 chromosomes and karyotypic formula of 10m + 32sm + 8a. In addition to the normal complement, we also observed the occurrence of B chromosomes in the 2 populations with intra- and interindividual variation ranging from 0 to 10 Bs, independent of sex. The C-banding pattern evidenced heterochromatic blocks located mainly in the pericentromeric region of the chromosomes, while the B chromosomes appeared euchromatic. Silver-stained nucleolus organizer regions were identified in multiples sites, and some of these blocks were positive when stained with chromomycin A3. The karyotype analysis and the application of whole-chromosome painting in populations of M. oligolepis reinforce the conservation of the basal diploid number for the genus, as well as the evolutionary tendency in these fishes to carry B chromosomes. Both populations turned out to be in different stages of stability and expansion of their B chromosomes. We further suggest that the origin of these chromosomes is due to the formation of isochromosomes. Here, we identified a pair of complement A chromosomes involved in this process. © 2021 S. Karger AG, Basel.
Luana Pereira Dos Santos, Carine M Francisco, Edimar O Campos Júnior, Jonathan P Castro, Ricardo Utsunomia, Sandra Morelli, Fábio Porto-Foresti, Fausto Foresti, Roberto F Artoni. Chromosomal Instability and Origin of B Chromosomes in the Amazonian Glass Tetra Moenkhausia oligolepis (Günther, 1864) (Characiformes, Characidae). Cytogenetic and genome research. 2021;161(5):249-256
PMID: 34433167
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