Comparative Study of the Ovarian Follicles in Hibernating and Nonhibernating Mammals

1 Institute of Cryobiology and Food Technology, BG - 1407 Sofia, Bulgaria
2 National Center of Hygiene, Medical Ecology and Nutrition, BG - 1431 Sofia, Bulgaria


TSVETKOV, Ts., V. STANCHEV and Ts. TAKEVA, 2004. Comparative Study of the Ovarian Follicles in Hibernating and Nonhibernating Mammals Bulg. J. Agric. Sci., 10: 409-416

Studied were the ovaries of a guinea pig, a rabbit, a ground squirrel and man. Tracked was the development of the ovarial follicles during the different stages of the estrous cycle in the different seasons in the hibernating mammal Citellus Citellus L., and before and after a provoked ovulation of a rabbit. Established were changes in the oocyte, the satellite cells and theca interna of the non-hibernating mammals with an estrous cycle, possessing similar characteristics. A difference was found in the rabbit, which has a provoked ovulation (the ovulation occurs 11 1/2 hours after the coitus). The tecocytes in the non-hibernators with an estrous cycle begin to luteinize in the proestrous phase, while in the rabbit that follows immediately the ovulation. The concentration of cortical granules under the plasma membrane of the oocyte proceeds parallel to the process of luteinization of the tecocytes. In the rabbit they are present in all mature follicles and for hours (approximately 11 hours) they increase considerably.
In the hibernating mammals theca interna begins to luteinize around one month before the spring awakening. Zona pellucida starts its formation as early as the primordial follicle and is completely finished in the primary follicle. Probably it is formed predominantly from the oocyte. The described multilamellar bodies bear a morphologically proven relation to the formation of the dictyosomes. The identification of the differences between the species is important for the elucidation of the process of reproduction and the related social problems.

Key words: hibernation, ovarian follicles, mammals