| Scope and method of study. My objective was to document the seasonal profile of plasma concentrations of the sex steroids, estradiol (E2), progesterone (P), testosterone (T), and glucocorticoid, corticosterone (CORT) in the Texas horned lizard (Phrynosoma cornutum).; Findings and conclusions. In comparison with other vertebrates, the seasonal steroid profile of P. cornutum exhibited both expected and unexpected patterns. Similar to other lizards, T reached peak concentrations in breeding males, suggesting that it plays a role in spermatogenesis and male sexual behavior. CORT did exhibit a significant seasonal effect for adult females. P showed no significant season effect for either sex. CORT also was marginally higher during the breeding season in adult males. Breeding males increase their movements in search of mates and egg-laying females expend energy searching for suitable nest sites and in development of their eggs, which demonstrates the need for additional energy provided by the increase in CORT. (Abstract shortened by UMI.)... |
