DESCRIPTIVE KINETICS OF THE SEMINIFEROUS EPITHELIUM CYCLE AND GENOME SIZE IN THE MOLE TALPA-OCCIDENTALIS (INSECTIVORA)

The male germ cell cytodifferentiative process of the mole Talpa occid entalis is described. Cytochemical procedures were used 1) to follow a crosome formation and spermatid differentiation, dividing the seminife rous epithelium cycle into ten stages, each characterized by typical g erm cell-to-cell associations, and recognizing 13 steps in spermatid d ifferentiation; 2) to monitor, in situ, histones replacement by protam ines at step 11 of the spermiogenic process. The seminiferous epitheli um cycle of the mole has the basic histological features present in al l mammals and appears rather similar to that of the common shrew (Sore x araneus), the only one so far known among Insectivora. The metabolis m of the DNA-associated proteins reveals that protamines replace histo nes during the late steps (11-13) of spermiogenesis, mRNA for protamin es having been synthesized at an earlier step (assuming that in the mo le this occurs at the first spermiogenic steps, as in the house mouse) . In addition the genome size (5.0 pg) and the AT/GC ratio (1.3) were evaluated. (C) 1995 Wiley-Liss, Inc.