Correspondence between C-banding and Ag-NOR in the Sex Chromosomes of Belostoma oxyurum (Belostomatidae, Heteroptera)

抄録

The mitotic and meiotic sex chromosomes of Belostoma oxyurum have been analyzed by C-banding and Ag-NOR staining. In mitotic prometaphases the Y chromosome and both telomeric regions of the X are C positive. However, at meiosis one telomeric region of the X chromosome presents always a C positive band, while the other telomeric region of this chromosome and the whole of the Y chromosome are light C banded during diplotene, the diffuse stage and early diakinesis. All these bands appear C positive by late diakinesis. In mitotic prometaphases, a positive Ag-NOR is revealed at one telomeric region of the X chromosome, but not in the Y chromosome. Besides, some intra and/or interindividual variation in NOR expression in the X chromosome is encountered. No positive Ag-NOR band is observed at meiosis.
A comparison of the results obtained in mitotic and meiotic cells after C- and Ag-NOR banding lead to the conclusion that in Belostoma oxyurum the intermediate staining of the C-bands of the sex chromosomes at meiosis is related to both the DNA composition (repetitive DNA, rRNA genes) and its packaging (cycle of condensation).