Corticosterone Treatment Has Subtle Effects on Thermoregulatory Behavior and Raises Metabolic Rate in the New Zealand Common Gecko, Hoplodactylus maculatus

Abstract

Baseline concentrations of adrenal glucocorticoids often vary substantially in wild vertebrates in the field. In at least one ectotherm, females of the New Zealand common gecko, Hoplodactylus maculatus, this variation in baseline (not stress-induced) corticosterone appears to be correlated with variation in body temperature (T(b)). We tested the hypothesis that elevated corticosterone affects thermoregulatory behavior so as to raise T(b) and that, independently of an increase in T(b), corticosterone increases metabolic rate. Compared with geckos receiving placebo implants, those that received implants containing corticosterone displayed heat-seeking behaviors, had a higher mean T(b) in their home cages, and, at one time of day, selected a higher mean T(b) in a thermal gradient. At a constant T(b), corticosterone-treated geckos consumed oxygen at a rate approximately 50% higher than placebo geckos. This work has far-reaching implications for a variety of physiological and ecological processes in ectotherms and suggests that corticosterone should be considered as a variable influencing T(b) and metabolism in future studies.

Hormonal and metabolic responses to upper temperature extremes in divergent life-history ecotypes of a garter snake

“…For example, glucocorticoids, such as corticosterone (CORT) in reptiles, can increase metabolic rate independent of temperature (Bradshaw, 2003;DuRant et al, 2008;Preest and Cree, 2008). In general, we expect that ambient temperatures that approach critical limits will induce an acute endocrine-driven stress response as an individual attempts to both survive and avoid permanent damage (McEwen and Wingfield, 2010;Romero et al, 2009).…”

Stress Ecology of the Pacific Rattlesnakes (Crotalus Oreganus and Crotalus Helleri)

“…Several studies have reported positive correlations between CORT and Tb in reptiles (Tyrrell and Cree 1998;Jessop et al 2000;Cree et al 2003;Woodley et al 2003) but due to the relationship between T b , metabolic rate, and CORT secretion (Landys et al 2006), it is unclear in these studies whether CORT is driving T b through effects on behavioral thermoregulation or whether T b drives CORT secretion through its effects on metabolic rate. Exogenous CORT treatment has revealed that in female geckos (Hoplodactylus maculatus), heat seeking behavior is increased following treatment (Preest & Cree 2008), while in wall lizards (Podarcis muralis) heat avoidance behavior is observed (Belliure & Clobert 2004). In support of our result, a study on translocated rattlesnakes reported lower mean T b during the week immediately after translocation than controls (Holding, Owen & Taylor 2014), which may be related to differences in circulating CORT, although this was not directly assessed (Holding et al 2014a).…”

Do Gravid Females Become Selfish? Female Allocation of Energy during Gestation

“…We expected to find strong effects of maternal net energy availability during gestation on offspring characteristics because both maternal plasma corticosterone concentration and maternal food availability during gestation affect maternal net energy gain (Preest and Cree 2008;Tsai et al 2009) and, therefore, the degree of reproductive investment. While it is possible that low food levels may have had a direct effect on maternal plasma corticosterone (Kitaysky et al 1999;Lynn et al 2010), given that the two treatments did not interact strongly, we are confident that our treatments altered female energy pathways in two independent ways as we intended.…”