LEVELS OF TESTOSTERONE IN THE PLASMA AND TESTIS OF THE VIVIPAROUS LIZARD (LACERTA-VIVIPARA JACQUIN) DURING THE ANNUAL CYCLE

Testosterone concentration in the plasma and testis were measured by radioimmunoassay in 90 males of viviparous lizards. Determinations were performed at twice monthly intervals from March to October during two annual cycles. Plasma level of testosterone reached a peak of 445 ng/ml in the mating season, then fell abruptly to the value of 2 ng/ml in July, rose in September, then remained at a similar level of approximately 30-40 ng/ml before and after hibernation. Testosterone levels in the testis followed the plasma values except in June when the testicular levels were high although the plasma concentrations were low. This period (June) is characterized by atrophy of the epididymis (secondary sexual character) and of the seminiferous tubules and precedes the renewal of spermatogenesis (early testicular recrudescence). The plasma values of testosterone and their range of variations in this species are the highest presently known in vertebrates. © 1979.