Meeting Abstract
The flight muscles of birds undergo multiple physiological changes during the transition from a nonmigratory to a migratory state. Both the hypothalamic-pituitary-adrenal and -gonadal (HPA/HPG) axes have been proposed to coordinate the physiological changes associated with this transition. For example, the HPA axis is thought to be associated with processes related to fueling migration, while the HPG axis is proposed to mediate flight muscle hypertrophy. However, the specific components of these endocrine signaling pathways that coordinate the physiological changes associated with the migratory transition are not well understood. We hypothesize that variation in the sensitivity of the flight muscles to steroid hormones produced by the HPG and HPA axes is important for coordinating the physiological changes that occur during the migratory transition. To assess this hypothesis, we used qPCR to quantify mRNA expression levels of genes for steroid hormone receptors associated with the HPA axis (mineralocorticoid and glucocorticoid receptors) and HPG axis (estrogen receptor alpha and androgen receptor) in the pectoralis muscle of captive, adult pine siskins (Spinus pinus). Samples were collected from captive subjects either prior to (i.e., during the winter) or after they entered the spring nomadic migratory state. By examining expression patterns of steriod hormone receptors across this migratory transition, this study adds to the growing body of literature aimed at understanding the endocrine mechanisms involved in coordinating the physiological changes associated with migration.
