- 1
- Department
of Ecology, Evolution, and Organismal Biology, Iowa State University,
Ames, IA 50011, USA. Electronic address: gangloff@iastate.edu.
- 2
- Department of Biology, Westmont College, Santa Barbara, CA 93108, USA.
- 3
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA.
Abstract
Characterizing
the baseline and stress-induced hormonal, metabolite, and immune
profiles of wild animals is important to assess the impacts of variable
environments, including human-induced landscape changes, on organismal
health. Additionally, the extent to which these profiles are coordinated
across physiological systems within individuals remains an important
question in understanding how stressors can differentially affect
aspects of an individual's physiology. Here, we present data from wild
populations of the common garter snake
(Thamnophis sirtalis) on both baseline and stress-induced biomarkers:
plasma corticosterone (CORT) concentration, plasma glucose
concentration, and whole blood heterophil:lymphocyte ratio. Using a
standardized restraint protocol with individuals from populations in
disparate portions of this species' range - the Sierra Nevada Mountains
of California and the plains of Iowa - we collected blood plasma samples
at nine time points over three days. Both CORT and glucose response
curves differed between georegions, with Iowa snakes attaining higher
glucose concentration and maintaining elevated CORT and glucose levels
for a longer duration. Additionally, both the total amount and
proportional increases of CORT and glucose were lower in larger and
therefore older snakes, suggesting ontogenetic shifts in stress
perception or response. Within-individual correlation among the three
physiological indicators was significant at the time of capture, absent
after 3h in captivity, and partially restored after 3days in captivity,
demonstrating the effect of stress on the relationships among these
physiological systems. Together, these results provide further evidence
for the great physiological flexibility of ectothermic tetrapods in
maintaining homeostasis across a range of factors.
Copyright © 2016 Elsevier Inc. All rights reserved.
KEYWORDS:
Allostasis; Corticosterone; Geographic variation; Glucose; Homeostasis; Hormones; Leukocyte
