Effects of Hypophysectomy on Folliculogenesis in the Tammar Macropus eugenii (Marsupialia: Macropodidae)

Abstract

The ovaries of 18 pouch young tammars 18-42 weeks old, and the ovaries of four sham-operated and four hypophysectomized adults, were serially sectioned and the follicle and oocyte diameters measured and atresia assessed. The relationship between oocyte and follicle diameter for each group of ovaries was best described by an exponential curve. There was an overall reduction in the number of normal follicles in the hypophysectomized tammars. with significant reduction of the smallest type (3b) and absence of the largest type (8), whereas there was a greater incidence of atresia in the penultimate type 7. These results suggest that only the latest stage offolliculogenesis is acutely pituitary-dependent, although in the longer term the pituitary may influence recruitment of preantral follicles. The ovaries of prepubertal tammars had fewer follicles of all types than the ovaries of intact adults but the incidence of atresia was higher in all except type 6. Like the ovaries of hypophysectomized adults they lacked type 8 follicles and had a high incidence of atresia ofthe penultimate type 7. It is concluded that up to 42 weeks the pituitary does not provide gonadotrophic stimulation to the ovaries of prepubertal tammars.