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Blubber steroid hormone profiles as indicators of physiological state in free-ranging common bottlenose dolphins (Tursiops truncatus)

Published

Author(s)

Thomas M. Galligan, Ashley S. Boggs-Russell, Brian C. Balmer, Teresa Rowles, Cynthia Smith, Forrest Townsend, Randall Wells, Nicholas Kellar, Eric Zolman, Lori Schwacke

Abstract

Assessing endocrine health in free-ranging marine mammals can be difficult due to limited access to blood samples, which is the most commonly used sample matrix for endocrine assessment in wildlife. Blubber contains steroid hormones and can be collected remotely via dart biopsies, which removes some of the logistical constraints associated with blood collection, meaning blubber could potentially be used in place of blood. To date, few studies have directly assessed the relationships between circulating versus blubber steroid hormone profiles in marine mammals. In this study, we measured a suite of steroid hormones via liquid-chromatography tandem-mass spectrometry (LC-MS/MS) in matched blood and blubber samples from free-ranging common bottlenose dolphins (Tursiops truncatus). Using principal components analysis (PCA), we explored relationships between hormones both within and across each matrix, and characterized hormonal changes associated with three physiological states: sexual maturity in males, pregnancy in females, and acute stress response. For the reproductive hormones, variable loading patterns indicated positive correlation between blood and blubber hormone profiles, and principal component score patterns aligned with expected physiological states. That is, plasma and blubber testosterone and its precursors, 17- hydroxyprogesterone and androstenedione, loaded to the first principal component (PC1), and PC1 scores were higher in mature males. Similarly, plasma and blubber progesterone (P4) loaded to PC2, and pregnant/probable pregnant females had significantly higher PC2 scores, which was expected considering that P4 is involved in maintaining pregnancy. Pregnant females also had higher PC1 scores compared to non-pregnant females. Conversely, there was disagreement between plasma and blubber corticosteroid (stress steroid) profiles, as indicated by their loading to different PCs. Plasma cortisol and cortisone loaded to PC3, while blubber cortisol, cortisone,
Citation
Comparative Biochemistry and Physiology A-Molecular & Integrative Physiology

Keywords

steroid hormone, blubber, marine mammal, bottlenose dolphin, LC-MS/MS
Created January 1, 2020, Updated February 4, 2020