CYTOGENETIC INVESTIGATIONS ON THE HOLOCENTRIC CHROMOSOMES OF TETRANEURELLA-AKINIRE (SASAKI) (HOMOPTERA, PEMPHIGIDAE)

The karyotype of the root aphid Tetraneurella akinire was analysed by means of C, G, and NOR banding. The overall base pair distribution was investigated after CMA, and DAPI fluorochrome staining. Both C and G treatments revealed a well defined banding pattern on the X and A1 chromosomes. C-bands showed a marked polymorphism in both size and number, even within the same individual. NOR banding produced a precipitation of silver on one telomere of the X chromosome, which also showed bright fluorescence after CMA, staining. Treatment with DAPI uniformly stained all chromosomes. Neither CMA3 nor DAPI showed bright fluorescence overlapping the C-positive bands. It can be concluded that T. akinire chromosomes present a cluster of GC-rich DNA sequences located on one telomere of the X chromosome, whereas the AT - sequences are regularly arranged along the chromosome axes and not grouped into well defined clusters.