Annual cycles of plasma and testicular androgens in the lizard Tiliqua (Trachydosaurus) rugosa

Abstract

Androgen production during the annual reproductive cycle was investigated in the male scincid lizard Tiliqua (Trachydosaurus) rugosa. Concentrations of testosterone and epitestosterone were measured in plasma and testis (incubated and nonincubated) using radioimmunoassay. Morphological and histological techniques were used to determine the anatomical changes in the testis. Mating behavior was observed during spring, and sperm were most numerous in the testis at this time. Histological evidence and changes in testicular weight indicated that spermatogenesis begins in autumn and culminates in spring. Testicular regression occurred soon after mating. Plasma concentrations of both androgens were maximal during spring and minimal during summer. The maximal concentrations were approximately 500 and 150 nmol/liter (epitestosterone and testosterone, respectively). The minimal plasma concentrations were 250 and 15 nmol/liter, respectively. Plasma and testicular androgen cycles followed a pattern similar to that of the spermatogenetic cycle, suggesting the possible involvement of one or both of these androgens in the control of spermatogenesis and mating behavior in these lizards. © 1986.