CHANGES IN NOR ACTIVITY PATTERN IN THE PRESENCE OF SUPERNUMERARY HETEROCHROMATIN IN TARE GRASSHOPPER EYPREPOCNEMIS-PLORANS

Nucleolus organizer region (NOR) activity was analysed in four types o f males of the grasshopper Eyprepocnemis plorans, possessing two kinds of supernumerary heterochromatin: a B chromosome and a supernumerary chromosome segment proximally located on the smallest autosome (S-11). In males lacking extra heterochromatin, the four active NORs located on the S-9, S-10, S-11, and X chromosomes showed independent activity patterns, but several kinds of dependence appeared in the presence of supernumerary heterochromatin. Furthermore, temporal changes in NOR ac tivity were observed during the first 2 weeks of adult life in standar d males but not in males carrying supernumerary heterochromatin. It is suggested that all these effects are related to the DNA content of bo th types of extra heterochromatin.