KINETICS OF SPERMATOGENESIS IN THE INDIAN-DESERT GERBIL, MERIONES-HURRIANAE (JERDON) - SEMINIFEROUS EPITHELIAL CYCLE, FREQUENCY OF STAGES, SPERMATOGONIAL RENEWAL AND GERM-CELL DEGENERATION

The present study provides information on the germ cell associations, the pattern of spermatogonial cell renewal, percentage frequency distr ibution of different cellular associations and germ cell degeneration in the adult gerbil, M. hurrianae. Based on the formation of acrosomal system and the development of the spermatids as visualized with PAS-h ematoxylin, 15 steps of spermiogenesis were identified. The first 12 s teps were associated with 12 stages, and the other three steps were be tween the first 6 stages. The relative frequency was maximal for stage VII (14.24) and minimal for stage VIII (4.38), indicating stage VII t o be of the longest and stage VIII of the shortest duration. On the ba sis of their shape, size and nuclear morphology, 6 types (A(0) A(1), A (2), A(3) In and B) of spermatogonia were identified in the gerbil. A- type spermatogonia are oval in shape. From A, and A, spermatogonia, pr ogressive heterochromatinization was evident. The A(3)-spermatogonia d ivide to give rise to In spermatogonia which are smaller than A-type c ells. The B-type spermatogonia are derived from In-type cells and are round in shape. These divide to give rise to first generation primary spermatocytes. Spermatogonia divide at fixed stages during the CSE, an d they exhibit 5 peaks of mitosis. A-type spermatogonia divide during stages VI, IX, XII and I. In- and B-Types divide during stages II and V respectively. During stages XII and I, A(3)-type cells divide to giv e rise to In- as well as to A(1)-type cells, thus restoring the A-sper matogonial population. In this way A(3)-cells serve to renew the stem cells. A-type spermatogonia showed 21.88%, 28.35% and 25% degeneration in stages VI, IX and XII and I respectively. In- type cells exhibited 24.53% at stage III, and B-spermatogonia showed 23.57% degeneration i n stage VI. Among the spermatocyte population more degeneration was fo und (36.43%) at the first meiotic division than at the second (4.62%). Hence, at the end of spermatogenesis, instead of the theoretically ex pected 64, 43.8 spermatids were formed, indicating a 31.5% loss in the number. Thus it is evident from the present study that degeneration o f germ cells during spermatogenesis plays an important role in determi ning the number of spermatozoa produced.