Seasonal variation in hormonal responses of timber rattlesnakes (<Emphasis Type="Italic">Crotalus horridus</Emphasis>) to reproductive and environmental stressors |
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Authors: | William I Lutterschmidt Deborah I Lutterschmidt Robert T Mason Howard K Reinert |
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Institution: | (1) Department of Biological Sciences, Sam Houston State University, Huntsville, TX 77341, USA;(2) Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA 30302, USA;(3) Department of Zoology, Oregon State University, Corvallis, OR 97331, USA;(4) Department of Biology, The College of New Jersey, Ewing, NJ 08628, USA |
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Abstract: | Data addressing adrenocortical modulation across taxonomic groups are limited, especially with regard to how female reproductive
condition influences the sensitivity of the hypothalamus–pituitary–adrenal axis. We investigated seasonal and reproductive
variation in basal and stress-induced hormone profiles in a population of free-ranging timber rattlesnakes (Crotalus horridus) in north-central Pennsylvania during spring (i.e., May), summer (i.e., July), and early fall (i.e., September). Baseline
corticosterone concentrations varied seasonally and were significantly lower during the summer sampling period in July. We
observed a significant negative relationship between baseline corticosterone and testosterone in male snakes, while baseline
corticosterone and estradiol tended to be positively correlated in females. Treatment of snakes with 1 h of capture stress
significantly increased corticosterone across all seasons. However, there was a significant interaction between corticosterone
responses to capture stress and season, suggesting that adrenocortical function is modulated seasonally. Because elevated
corticosterone may be associated with reproduction, we asked whether hormonal stress responses vary with female reproductive
condition. Although sample sizes are low, reproductive snakes had significantly higher baseline and stress-induced corticosterone
concentrations than non-reproductive or post-parturient females. Further, despite similar baseline corticosterone concentrations
between non-reproductive and post-parturient rattlesnakes, post-parturient females responded to capture stress with a significantly
higher increase in corticosterone. Collectively, these data suggest that the sensitivity of the hypothalamus–pituitary–adrenal
axis varies both seasonally and with changing reproductive states. |
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Keywords: | Reproduction Capture stress Corticosterone Testosterone Estradiol |
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