Response to capture stress involves multiple corticosteroids and is associated with serum thyroid hormone concentrations in Guadalupe fur seals (Arctocephalus philippii townsendi)

Abstract

Guadalupe fur seals are a threatened species with few breeding locations, which potentially makes them sensitive to environmental or anthropogenic stressors. We present the first study to quantify adrenal and thyroid function in this species in an effort to measure their stress response to capture. We analyzed a suite of corticosteroid hormones released over time during capture in both adult females (n = 10) and weanling pups (n = 26) during March 2016. Multiple corticosteroids were released during capture, and aldosterone was associated with the response to stress in adults only. These results suggest the regulation of aldosterone secretion in association with the HPA axis in otariids as reported in other marine mammals. Individuals varied markedly in the magnitude of their endocrine response to capture. A lower total integrated stress response to capture for both cortisol and corticosterone was associated with decreased concentrations of thyroid hormone T3 and elevated concentrations of reverse T3 (rT3), suggesting parallel downregulation of adrenal and thyroid endocrine axes in some individuals. A scaled body condition index was negatively associated with T3 and positively associated with rT3 in adults. Together these findings suggest utility in using endocrine responses to capture stress to evaluate individual and population health.

Stress-related and reproductive hormones in hair from three north Pacific otariid species: Steller sea lions, California sea lions and northern fur seals

“…Interestingly, 40% of California sea lions and northern fur seals and 27% of Steller sea lions had F:B ratio < 1.0. The variability in the GC ratios we found were not completely surprising as a recent study found the F:B ratios in serum ranged between 6.5 and 16.2 in Guadalupe fur seals during an acute stress response ( DeRango et al , 2018 ). We also found cortisol and corticosterone were correlated, explaining between 58 and 63% of the variability in the three otariid species.…”

“…Assessing the impact of potential stressors in pinnipeds is logistically challenging and often requires capture and handling ( DeRango et al , 2018 , Keogh et al , 2013 ). Many stress-related hormones can be altered during this process, thus limiting the utility of metabolically active tissues, such as blood ( Atkinson et al , 2015 ).…”

“…The hypothalamic–pituitary–adrenal (HPA) axis activates in response to a stressor leading to the secretion of glucocorticoids (GCs) and a suite of behavioural and physiological changes ( Atkinson et al , 2015 , Sapolsky et al , 2000 , Wingfield et al , 2003 , Wingfield, 2005 ). Further in pinnipeds, aldosterone is influenced by the HPA axis in response to acute stressors ( DeRango et al , 2018 , Gulland et al , 1999 , Keogh et al , 2015 ). In fact, following an adrenocorticotropic hormone (ACTH) injection, serum aldosterone concentrations increased more rapidly and showed a greater fold increase compared circulating cortisol concentration ( Keogh and Atkinson, 2015 ).…”

“…In fact, following an adrenocorticotropic hormone (ACTH) injection, serum aldosterone concentrations increased more rapidly and showed a greater fold increase compared circulating cortisol concentration ( Keogh and Atkinson, 2015 ). Similarly, capture stress induced an increase in circulating aldosterone, cortisol, and corticosterone concentrations in adult Guadalupe fur seals ( Arctocephalus philippii townsendi ) ( DeRango et al , 2018 ). Thus, circulating stress-related hormones measured in blood are influenced by many factors that may be outside the aims of a study and only provide a snapshot of the physiology of an animal.…”

Chronic stress from fishing gear entanglement is recorded in baleen from a bowhead whale (Balaena mysticetus)

“…Additional research on a larger number of whales of differing sex and age-class is needed to determine the relative responsiveness of both GCs to different types of both natural (e.g., pregnancy, lactation) and anthropogenic stressors, to develop a reference dataset of baleen GC levels, and to better understand the biological relevance and temporal aspects of increased baleen hormone concentrations. Recent research on both terrestrial and marine species has suggested that the two GCs may signal independently, and, therefore, studies of acute and chronic stress should include analysis of both hormones (Koren et al 2012, Chinn et al 2018, DeRango et al 2019.…”