Effects of Adenohypophysectomy on Testicular Function in the Lizard Anolis carolinensis

About 300 adult male lizards, Anolis carolinensis, measuring over 59 mm in snout-vent length were used in studying the role of the pars distalis in controlling testicular function. Both maintenance and development of the germ cells and androgen production depend on the adenohypophysis. Rapid regression in testicular size and spermatogenic activity follow removal of the pars distalis in animals kept at 31 C. Germ cells begin degenerating within 2 days, and all except a few spermatogonia are lost within 10 days. Regression is complete within 14 days; enlarged testes decrease from 35 to 2 mg. Autoradiographic studies demonstrate that in intact animals spermatogonia develop to the stage of transforming spermatids within 14 days; thymidine uptake by germ cells ceases within 4 days after hypophysectomy. The rate of regression is highly temperature dependent, and only slight changes occur in the testes within 21 days after hypophysectomy at 20 C. Short daylengths effect a“physiological” hypophysectomy at 31 C during October. Studies of testis function after removal of different parts of the pars distalis fail to support claims of two separate gonadotropes with restricted distributions in the pars distalis of reptiles. Testes develop normally at 31 C as long as any 50% of the gland remains intact. Testes weights remain stationary or decline when larger amounts of the gland are removed, but all stages of spermatogenesis and hypertrophy of the epididymis occur as long as at least 20% remains. The production of some spermatocytes continues as long as 10% of the gland remains, and these effects are independent of the region of the gland removed.