文獻來源: Kantek D. L. Z., Noleto R. B., Maurutto F. A. M., Bertollo L. A. C., Moreira-filho O., Cestari M. M. 2008. Cytotaxonomy of Astyanax (Characiformes, Characidae) from the Upper Iguaçu River Basin: confirmation of the occurrence of distinct evolutionary units. Journal of Fish Biology 73(8): DOI: 10.1111/j.1095-8649.2008.02030.xABSTRACT
Taxonomic studies of the genus Astyanax from the Iguaçu River (Brazil) indicate that they may be differentiated into 11 distinct species, some of which have not been formally described and named so for. This study focuses on three of these species, Astyanax sp. B, Astyanax sp. C and Astyanax sp. D from the Upper Iguaçu River Basin. Comparative cytogenetic analyses of C-banding, Ag-NORs (silver nitrate stained nucleolar organizer region) and 18S and 5S rDNA corroborate that they are distinct species. A diploid number of 50 chromosomes and similar karyotypic formulae were observed in the three taxa, with the exception of Astyanax sp. D that differs in the number of submetacentric and subtelocentric chromosomes. However, the NOR silver-staining pattern, the heterochromatic bands (C-bands) and the mapping of the 18S and 5S rDNA sites in the chromosomes showed divergences between all three species under study, supporting the occurrence of distinct evolutionary units.
圖片連結: The Age of Aquariums (credit Helios Medina)
