title: Derived cytogenetic traits, multiple NORs and B chromosomes in the compact karyotype of Canthigaster figueiredoi (Tetraodontiformes).
abstract: 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-CMA(3), and in situ hybridization with 18S rDNA probe. This species has 2n=36 (10 m+6sm+20a; FN=52). Multiple Ag-NORs (CMA(3)(+)) sites were detected on the four chromosome pairs. Heterochromatic blocks (CMA(3)(+)) were present in the centromeric regions of most of the pairs, extending on the short arm of some chromosomes. A GC-positive 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.
authors.affiliation: Universidade Federal do Rio Grande do Norte (UFRN), Departamento de Biologia Celular e Genética, Centro de Biociências, Lagoa Nova s/n, CEP 59078-970, Natal, Rio Grande do Norte, Brasil. pablo_sc82@hotmail.com
authors.forename: Pablo Ariel
authors.initials: PA
authors.lastname: Martinez
authors.forename: Washington Candeia
authors.initials: WC
authors.lastname: de Araujo
authors.forename: Wagner Franco
authors.initials: WF
authors.lastname: Molina
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics; D001938:Brazil; D002875:Chromosomes / Q000235:genetics*; D020732:Cytogenetic Analysis; D005260:Female; D017403:In Situ Hybridization; D007211:Indoles; D059785:Karyotype; D008297:Male; D008856:Microscopy, Fluorescence; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D023721:Tetraodontiformes / Q000235:genetics*
chemical_list: D034961:Antigens, Nuclear; D007211:Indoles; D012337:RNA, Ribosomal, 18S; C051963:nucleolar organizer region associated proteins; C007293:DAPI