The Tetraodontiformes are one of the main irradiation lineages of Teleosts representing a highly specialized
group. Among its families, Tetraodontidae has the lowest DNA/cell content of the vertebrates, and for this
reason has been used as a model group for genomic evolution studies. Seeking to widen the cytogenetic
database of this family, we performed a chromosomal analysis of the species Canthigaster figueiredoi using
conventional staining, Ag-NORs, C-banding, base-specific fluorochromes DAPI-CMA3, and in situ hybridization
with 18 S rDNA probe. This species has 2n=36 (10 m+6sm+20a; FN=52). Multiple Ag-NORs
(CMA3+) sites were detected on the four chromosome pairs. Heterochromatic blocks (CMA3
+) were present in the centromeric regions of most of the pairs, extending on the short arm of some chromosomes. A GCpositive polymorphic heterochromatic region was identified in some of the individuals, in one or both of the
homologs of the 6th pair. The presence of heteromorphic B microchromosomes was detected in the
karyotype of one female, exhibiting intra-individual variation of 0–3 Bs. The occurrence of heterochromatic
polymorphisms, multiple NORs, and B chromosomes in C. figueiredoi are very infrequent events in marine
fish. They are probably associated to the accentuated restructuring and genomic reduction suffered by this
family.
The Tetraodontiformes are one of the main irradiation lineages of Teleosts representing a highly specialized
group. Among its families, Tetraodontidae has the lowest DNA/cell content of the vertebrates, and for this
reason has been used as a model group for genomic evolution studies. Seeking to widen the cytogenetic
database of this family, we performed a chromosomal analysis of the species Canthigaster figueiredoi using
conventional staining, Ag-NORs, C-banding, base-specific fluorochromes DAPI-CMA3, and in situ hybridization
with 18 S rDNA probe. This species has 2n=36 (10 m+6sm+20a; FN=52). Multiple Ag-NORs
(CMA3+) sites were detected on the four chromosome pairs. Heterochromatic blocks (CMA3
+) were present in the centromeric regions of most of the pairs, extending on the short arm of some chromosomes. A GCpositive polymorphic heterochromatic region was identified in some of the individuals, in one or both of the
homologs of the 6th pair. The presence of heteromorphic B microchromosomes was detected in the
karyotype of one female, exhibiting intra-individual variation of 0–3 Bs. The occurrence of heterochromatic
polymorphisms, multiple NORs, and B chromosomes in C. figueiredoi are very infrequent events in marine
fish. They are probably associated to the accentuated restructuring and genomic reduction suffered by this
family.
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