Ovarian activity during the annual reproductive cycle and nesting cycle of a wild avian species, the pied myna (Sturnus contra contra)

Ovarian activity was studied during the annual reproductive cycle and nesting cycle in the Indian pied myna (Sturnus contra contra). The investigation was carried out on the basis of gravimetric, histological (gross and quantitative), and histochemical (3β-hydroxysteroid dehydrogenase and lipids) studies. In the ovary of the pied myna, four types of healthy follicles (primordial, small developing, large developing, and yolky) were recognized; the stroma showed gland cells. Steroidogenic activity was marked in the theca and granulosa of the follicles, and it altered with the growth of the follicles. The probable source of stromal gland cells is discussed. The ovarian activity changed over the course of the year with four distinct phases, viz., progressive (February to April), breeding (May), regression (June to July), and nonbreeding (August to January) phases. Ovarian weight, largest follicular diameter, populations of larger follicles, and thecal gland cell mass increased gradually from February through April, became maximal in May, decreased in June and July, and became minimal during August through January. Yolky follicles developed only in May. Stromal gland cell mass was abundant in March, decreased from April to June, was almost absent from July to September, reappeared in October, and gradually increased afterwards. Steroidogenic activity of the thecal and stromal gland cells also changed with the annual ovarian cycle; it was absent during July through September and reappeared in October. The granulosa cells showed steroid activity only in May. During the nesting cycle, ovarian activity increased rapidly from early nest-building to egg-laying periods and declined during incubation and nestling periods; this was evident from changes in ovarian weight, largest follicular diameter, thecal gland mass, and populations of larger follicles. Yolky follicles were seen during late nest-building, egg-laying, and incubation periods. Stromal gland cell mass decreased gradually during the nesting cycle. 3β-Hydroxysteroid dehydogenase activity was maximal in the nest-building period.

Ovarian cycle and reproductive dynamics in the female adder, Vipera berus (Reptilia, Viperidae)

Studies of reproductive organs, fat body and liver in relation to different activity periods were made to describe the breeding biology of the female adder, Vipera berus, in SW Sweden. The female adder is a biennial breeder. Vitellogenesis and formation of preovulatory follicles start in autumn the non-reproductive year and continue to the end of May the following spring when ovulation takes place. Copulation precedes ovulation and sperm is found in uterus a month before ovulation. Primary oocytes were seen after ovulation in the reproductive year. Atresia were seen more frequently during reproductive years and in all classes of follicles. Clutch size (X=8.8) had a linear increase with female body size and juveniles were born in early August. Thecal gland cells increased in number and the epithelium of the uterus became hypertrophied late in the non-reproductive year and early in the reproductive year. The weight of the ovary, fat body and liver went through a cyclic pattern with the highest peak in the reproductive spring. Fat body and liver weights were lowest at the end of the gestation period. Feeding periods, fat mobilization, reproductive effort, endocrine ectivity and adaptive value of the biennial reproduction are discussed. The adaptation to short season habitats is stressed.