The First Chromosomal Characteristics of Nucleolar Organizer Regions (NORs) in Grey Featherback Fish, Notopterus notopterus (Osteoglossiformes, Notopteridae) by Conventional and Ag-NOR Staining Techniques

The first chromosomal characteristic of nucleolar organizer regions (NORs) and karyological analysis of the grey featherback fish (Notopterus notopterus) from Chi basin, northeast Thailand, were studied. Kidney cell samples were taken from 4 male and 4 female fish. The mitotic chromosome preparations were done directly from kidney cells. Conventional and Ag-NOR staining techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of N. notopterus was 2n=42, the fundamental number (NF) was 42 in both males and females. The types of chromosomes were 8 large telocentric, 12 medium telocentric and 22 small telocentric chromosomes. The secondary constriction (NORs) was observed at the region adjacent to the centromere of the long arms of a pair of telocentric chromosome. The karyotype formula for N. notopterus is as follows:

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