Cytogenetic analyses of two endemic fish species from the São Francisco River basin: Conorhynchus conirostris and Lophiosilurus alexandri (Siluriformes)

Genetics and Molecular Biology

Marilza Barbosa De Almeida Marques²  Orlando Moreira-filho¹  Caroline Garcia¹  Vladimir Pavan Margarido¹ 

[1] ,Fundação Municipal de Educação e Cultura de Santa Fé do SulSanta Fé do Sul SP ,Brazil

关键词: incertae sedis;    Pimelodidae;    Pseudopimelodidae;    rDNA;    Siluriformes;   

DOI  :  10.1590/S1415-47572008000200008

来源: SciELO

【 摘 要 】

Two Siluriformes species endemic to the São Francisco River basin were characterized by conventional and differential cytogenetic analyses involving C-banding, Ag-nucleolar organizer region (NOR) and chromomycin A3 (CMA3) staining, and FISH (fluorescent in situ hybridization) with 18S and 5S rDNA probes. Conorhynchus conirostris presents a higher diploid number (2n = 60) than those detected in Pimelodidae representatives, whereas Lophiosilurus alexandri, with a karyotype of 2n = 54 chromosomes, presents a chromosomal constitution similar to that found in the family Pseudopimelodidae. Plesiomorphic characteristics such as single NORs at terminal positions are found in both species, as revealed by CMA3 and silver nitrate staining, and FISH with a 18S rDNA probe. C-banding evidenced centromeric and telomeric heterochromatic blocks distributed over most of the chromosomes with a conspicuous heterochromatin segment in a pair of submetacentric chromosomes in L. alexandri. Such karyotype data, if compared to the cytogenetic pattern of other Siluriformes species, can be partially related to their degree of endemism, favorable to the occurrence and fixation of chromosomal rearrangements. The present study in representatives from these two Siluriformes families from the São Francisco River contributes to a better understanding of the karyotype evolution in species of this important order of Neotropical fishes.

【 授权许可】

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