HETEROCHROMATIN HETEROGENEITY AND RAPID DIVERGENCE OF THE SEX-CHROMOSOMES IN CHORTHIPPUS-PARALLELUS PARALLELUS AND C P ERYTHROPUS (ORTHOPTERA)

Mitotic chromosomes from individuals of a Pyrenean hybrid zone between two subspecies of the grasshopper Chorthippus parallelus have been pr etreated as for C-banding and subsequently stained with 4,6-diamidino- 2-phenylindole (DAPI) and (or) Chromomycin A3 (CMA). The results, whic h are different from those obtained with Giemsa C-banding or standard DAPI - CMA treatments show (i) hidden heterochromatic heterogeneity th at may be correlated with the existence of distinct families of repeti tive DNAs, (ii) information about the possible independent origin of t he three detected types of heterochromatin, and (iii) a further marker difference between the sex chromosomes of these two subspecies. This last result leads us to discuss the possible differential rates of evo lution of sex chromosomes and autosomes in these subspecies and provid es us with a new tool for the study of the structure and dynamics of t his hybrid zone.