Relations between the Reproductive Cycle and the Pituitary Gland in the Snake Thamnophis radix

Abstract

The pars anterior shows zonation of 3 types of cells: acidophiles, basophiles, and chromophobes. Two types of acidophiles are described. Basophiles are grouped into light-blue and deep-blue cells, for convenience. The [female] has fewer basophiles during the reproductive peak than the [male]. This constitutes a sex difference. However, the basophile number of the mature virgin [female] is more nearly like that found in the [male]. The pituitary of the castrate d1 after 124 days shows a threefold increase in basophiles, which is slightly greater than the increase in the normal [male]. There are seasonal changes in the pituitary of both sexes: Coarse acidophiles are present throughout the yr.; they are abundant during the period of activity and scattered during hibernation. Pink acidophiles in the chromophobe area in the [male] are present in the spring, becoming fainter in the summer and fall; they are present in the nonpregnant [female] in the spring and the pregnant [female] and absent in both sexes during hibernation. Deep-blue basophiles are present in the summer, fall, and during hibernation and in the spring give rise to the dominant large light-blue basophiles. Light-blue basophiles, dominant in the spring, show extensive degranulation; they are relatively fewer during the summer and during hibernation In both sexes there are 2 peaks in the number of basophiles: They have nearly the same seasonal onset and regression. Regression in the spring is correlated with marked gonadal activity; in the fall, with ovo-cyte growth and increase in interstitial cell size. The hibernation peaks are similar and cannot be associated with gonadotrophic activity. The peaks during reproduction differ (sex difference), and secretory activity is present. A slight fluctuation in basophile number during early pregnancy may be associated with the appearance of the new 3d group of ovocytes. Animals hypophysectomized for a period of 9, 16, 44, and 66 days during the summer peak in basophile number showed a progressive atrophy and aplasia of the testis. July pituitary homeo-implants produced a 105% increase in testis wt. over a period of 9 days in hypophysectomized snakes. A total of 350 I.U. of equine gonadotrophin over a period of 16 days increased testis wt. 84% in hypophysectomized snakes. In both groups spermatogenesis and interstitial cells were stimulated. The maximal vol. of the testis is from 500 to 990% greater than the minimal vol., and the maximal wt. is 430% greater. Spermatogenesis occurs as a complete wave during the late spring and summer, with the most pronounced activity during June and July, which is associated with the maximal wt. and vol. of the testis. Spermiogenesis is pronounced in Aug., with a secondary wave in late Oct. Sperm are stored in the ductus deferens during hibernation and are utilized the following spring. Interstitial cells show seasonal changes in size staining, and cytology. Three macroscopic groups of ovocytes show differential growth and ovulate in succeeding seasons. Corpora lutea persist during a 9-wk. gestation period, regress after parturition in Aug., and leave corpus luteum scars. The avg. number of young in 33 [female][female] is 13. Embryonic development ceases under hibernating conditions.