Meeting Abstract
Individuals vary in circulating baseline levels of stress hormones (predictive homeostasis) and in their response to a stressor (reactive homeostasis). However, variation in normal reactive scope – predictive and reactive homeostasis combined – may be particularly important in females when in different reproductive states, such as gestating versus non-gestating females. The normal reactive scope of an individual is measured as the increase in glucocorticoid (GCs) hormones above baseline levels. We performed an adrenocorticotropic hormone (ACTH) challenge on females of the live-bearing fish species, Poecilia latipinna, at different reproductive states and measured stress responses using water-borne hormone collection methods. We measured cortisol, the primary GC in teleosts, to obtain baseline release rates prior to injection with either ACTH or saline. Then we measured cortisol release rates at three time intervals post-injection. Females were then sacrificed to determine the presence embryos. We found that non-gestating females had higher baseline cortisol release rates than gestating females, which suggests that baseline cortisol may be suppressed during gestation. Additionally, all ACTH-injected females, whether gestating or not, had higher release rates of cortisol during the second hour post-injection than females that received a saline control injection. These results provide insight into individual variation of the reactive scope and how individual reproductive states may affect that variation.
