PYCNOTIC CYCLE OF THE SEX-CHROMOSOME OF PYRGOMORPHA-CONICA (ORTHOPTERA) AND DEVELOPMENT OF SPERMIOGENESIS

We have analyzed the anomalous pycnotic cycle of the X sex chromosome of the grasshopper Pyrgomorpha conica throughout both meiotic division s and its possible influence on spermiogenesis. During diplotene the s ex chromosome shows two differentiated pycnotic regions: (i) the centr omeric region, which is negatively heteropycnotic, and (ii) the noncen tromeric region, which shows alternating negatively and positively het eropycnotic zones in all standard individuals. The variation in size a nd location of the negative heteropycnotic zones, their smooth appeara nce, and their lack of effect on spermiogenesis lead us to suggest tha t condensation differences and not euchromatinization are responsible for their presence. In two individuals the sex chromosome appeared par tially isopycnotic at metaphase I, and high levels of abnormal spermat ids (macrospermatids and microspermatids) were found. We suggest that the possible activity of this chromosome during the second meiotic div ision may promote the disruption of spermiogenesis by affecting the me chanism that maintains intercellular bridges between normal spermatids .