Karyotypical characterization from stock of Nile tilapia, Oreochromis niloticus, at Londrina State University, PR, Brazil, through several techniques of chromosomes band

摘要

A total of 14 specimens of Nile tilapia (Oreochromis niloticus) were analysed cytogenetically. These fish belonged to the stock for fish breeding in the Freshwater Aquaculture Station of Londrina State University in Parana, Brazil. All the specimens presented the same diploid number of 44 chromosomes. The nucleolus organizing regions (NORs) were observed in 4 chromosomes with marks in the terminal position of the short arm. Moreover, in situ hybridization (FISH) with probe of 18S also showed the presence of 2 pairs of chromosomes containing ribosomic cistrons. The treatment with the fluorochromes CMA3 and DAPI, respectively, did not show shining bands in any chromosome of the complement. The band C (CBG) showed regions of heterochromatin distributed on several chromosomes in the centromeric regions. Some marks in telomeric regions, mainly on the biggest pair of chromosomes of the complement, were observed. A pair presented itself as almost totally heterochromatic. The results were in accordance with the data found in literature. However, when the C bands and NORs were analysed, some differences that apparently characterized the local fish population of the Londrina State University were observed..