Ovarian and adrenal function in the parthenogenetic whiptail lizard Cnemidophorus uniparens in the field and laboratory.

The purpose of this study was to document circulating concentrations of corticosterone in the plasma in relation to the ovarian follicular cycle in animals in the field and to examine the effects of captivity and laboratory manipulations on plasma corticosterone in the parthenogenetic whiptail lizard Cnemidophorus uniparens. In nature, circulating concentrations of corticosterone are highest in previtellogenic individuals when concentrations of progesterone are basal and estradiol-17 beta is undetectable. In vitellogenic lizards, circulating concentrations of corticosterone decline from previtellogenic levels while concentrations of progesterone and estradiol-17 beta increase. In preovulatory individuals, corticosterone concentrations are basal, while progesterone and estradiol-17 beta levels are maximal. Following ovulation, corticosterone and progesterone remain at preovulatory concentrations and estradiol-17 beta is undetectable. Ovariectomy elevates circulating concentrations of corticosterone, as does cold and handling. Individuals housed either in isolation or in groups of three per cage exhibit circulating concentrations of corticosterone similar to those measured in the plasma of animals immediately after being captured in the field. The effects of ovariectomy and cold/handling manipulations were additive. No nonadditive effect (statistical interaction) was revealed. These results document complementary and reciprocal effects of ovarian and adrenal gland function with respect to hormonal changes both in the field and as a result of experimental manipulations in the laboratory. However, relationships between ovarian and adrenal function appear to be complex. Several overlapping hypotheses are offered as possible explanations of the results and as potential avenues for further investigations.