Dear MARMAM,
My co-authors and I are happy to present the new publication:
Eugene J DeRango, Katherine C Prager, Denise J Greig, Amanda W Hooper,
Daniel E Crocker, Climate variability and life history impact stress,
thyroid, and immune markers in California sea lions (Zalophus californianus) during El Niño conditions, Conservation Physiology, Volume 7, Issue 1, 2019, coz01.
Abstract:
Wildlife is exposed to a diverse set of extrinsic and intrinsic
stressors, such as climatic variation or life history constraints, which
may impact individual health and fitness. El Niño and climatic
anomalies between 2013 and 2016 had major ecological impacts on the
California Current ecosystem. As top marine predators, California sea
lions (CSL) experienced decreased prey availability and foraging
success, impacting their nutritional state. We hypothesize that chronic
stress to juvenile CSL increased during the 2015–2016 El Niño and that
breeding represents a period of chronic stress for adults, which impact a
variety of physiological processes. We opportunistically captured and
sampled juvenile CSL (female, n = 29; male, n = 38) in central California and adult male CSL (n = 76)
in Astoria, Oregon and quantified a suite of analytes in serum as
indicators of acute stress markers, metabolism and thyroid function, and
adaptive immune response. We found that stress hormones and glucose
were decreased in juvenile CSL during 2016 relative to 2015 and in adult
male CSL after the breeding season, which may indicate chronic stress
downregulating HPA (hypothalamic-pituitary-adrenal) axis sensitivity
with associated metabolic impacts. Conversely, thyroid hormones for both
juvenile and adult male CSL were increased, suggesting greater
energetic requirements resulting from increased foraging activity during
suboptimal conditions in juveniles and breeding tenure in adult males.
Immunoglobulin IgG was elevated in juveniles in 2016 but reduced in
adult males post-breeding. This suggests that juveniles may face
immunostimulatory pressure during anomalously warm ocean environments;
however, for adult males, breeding is a significant energetic cost
resulting in reductions to immune function. Our results indicate that
environmental conditions and life history stage may influence
physiological responses in an important marine predator and a sentinel
species of changing ocean ecosystems.
Best regards,
Geno DeRango
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PhD Student
Bielefeld University
Galapagos sea lion Project