TY - JOUR
T1 - Evidence for condition mediated trade-offs between the HPA- and HPG-axes in the wild zebra finch
AU - Crino, Ondi L.
AU - Jensen, Sophia M.
AU - Buchanan, Katherine L.
AU - Griffith, Simon C.
PY - 2018/4/1
Y1 - 2018/4/1
N2 - Opportunistic breeding is a strategy used to maximize reproductive success in unpredictable environments. Birds that breed opportunistically are thought to maintain partial activation of the reproductive axis in order to rapidly initiate breeding when environmental conditions become suitable. The physiological mechanisms that modulate reproduction in seasonally breeding birds have been well explored. In contrast, the physiological mechanisms that allow opportunistic breeding birds to maintain a continued state of reproductive readiness has not been well established. Here, we tested the hypothesis that reproductive readiness is modulated through condition-mediated effects on the hypothalamic–pituitaryadrenal (HPA) axis and its downstream effects on corticosterone (CORT) secretion in wild zebra finches (Taeniopygia guttata). We examined the variation in body condition, HPA-axis activity (endogenous and adrenocorticotropic hormone (ACTH)-induced responses), and hypothalamic-pituitary-gonadal (HPG) axis activity activity (baseline and gonadotropin-releasing hormone (GnRH) induced testosterone and estradiol levels) in zebra finches across five sites in the Northern Territory in Australia. We found that birds at the sites in the lowest condition had the highest level of baseline and peak CORT. Additionally, males at the sites in the lowest condition had the highest fold increase in testosterone following a GnRH challenge. Across sites, birds with low body condition had high baseline, peak, and ACTH-induced levels of CORT. Our data suggest that reproductive readiness in opportunistically breeding birds is modulated by condition-mediated trade-offs between the HPA- and the HPG-axes. Further work is needed to understand the environmental conditions that influence reproductive activation in opportunistically breeding birds.
AB - Opportunistic breeding is a strategy used to maximize reproductive success in unpredictable environments. Birds that breed opportunistically are thought to maintain partial activation of the reproductive axis in order to rapidly initiate breeding when environmental conditions become suitable. The physiological mechanisms that modulate reproduction in seasonally breeding birds have been well explored. In contrast, the physiological mechanisms that allow opportunistic breeding birds to maintain a continued state of reproductive readiness has not been well established. Here, we tested the hypothesis that reproductive readiness is modulated through condition-mediated effects on the hypothalamic–pituitaryadrenal (HPA) axis and its downstream effects on corticosterone (CORT) secretion in wild zebra finches (Taeniopygia guttata). We examined the variation in body condition, HPA-axis activity (endogenous and adrenocorticotropic hormone (ACTH)-induced responses), and hypothalamic-pituitary-gonadal (HPG) axis activity activity (baseline and gonadotropin-releasing hormone (GnRH) induced testosterone and estradiol levels) in zebra finches across five sites in the Northern Territory in Australia. We found that birds at the sites in the lowest condition had the highest level of baseline and peak CORT. Additionally, males at the sites in the lowest condition had the highest fold increase in testosterone following a GnRH challenge. Across sites, birds with low body condition had high baseline, peak, and ACTH-induced levels of CORT. Our data suggest that reproductive readiness in opportunistically breeding birds is modulated by condition-mediated trade-offs between the HPA- and the HPG-axes. Further work is needed to understand the environmental conditions that influence reproductive activation in opportunistically breeding birds.
KW - ACTH challenge
KW - Australia
KW - bird
KW - corticosterone
KW - estradiol
KW - GnRH challenge
KW - opportunistic breeding
KW - testosterone
KW - unpredictable environments
UR - http://www.scopus.com/inward/record.url?scp=85041917305&partnerID=8YFLogxK
U2 - 10.1016/j.ygcen.2017.11.025
DO - 10.1016/j.ygcen.2017.11.025
M3 - Article
C2 - 29197553
AN - SCOPUS:85041917305
SN - 0016-6480
VL - 259
SP - 189
EP - 198
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
ER -