Testosterone and reproductive activity in the male tegu lizard, tupinambis merianae

Abstract

In this study, we examined plasma testosterone levels in male Tupinambis merianae lizards and their relation to the seasonal reproductive activities observed in this species. We found that the highest androgen levels were associated with reproductive activity in spring, comprising sperm production, reproductive behaviors (territoriality, courtship, and matings), and secretory activities of femoral glands and kidney sexual segment. We observed an additional rise of testosterone in the fall that correlated with a secondary phase of testicular recrudescence, but which was not accompanied by reproductive behaviors or by secretory activities of the femoral glands and kidney sexual segment. The absence of sperm in the seminiferous tubules and epididymis during the cold months indicates that spring matings of T. merianae, as in most lizards, are supported by prenuptial spermatogenesis. Besides its association with high levels of circulating androgens, the spring breeding events coincide with an increase in environmental temperatures. Both spermatogenic waves also coincide temporally with the equinoxes. Further studies are necessary to establish the relative contributions of endocrine and environmental factors in triggering reproductive events in this species. We believe that this second non-functional spermatogenic wave may be a remnant of an ancestral bimodal reproductive cycle in this species.