The Effects of Low Temperature, and Cortisol, on Testicular Regression in the Hypophysectomized Cyprinodont Fish, Fundulus Heteroclitus

Low temperature retarded the rate of sexual regression in hypophysectomized male Fundulus heteroclitus. 2. Transfer to warm temperature accelerated the rate of post-spermatogonial regression, and the partially regressed interstitial tissue became inactive. 3. In contrast, the return to warm temperature stimulated the rate of spermatogonial mitosis. It is suggested that temperature has a direct action on spermatogonial multiplication. 4. Cortisol, at a physiological dose, had no significant effect on the condition of the testes.