Blubber cortisol qualitatively reflects circulating cortisol concentrations in bottlenose dolphins

Abstract

Stress hormones, released into circulation as a consequence of disturbance, are classically assayed from blood samples but may also be detected in a variety of matrices. Blubber and fecal samples can be remotely collected from free‐ranging cetaceans without the confounding hormone elevations associated with chase, capture, and handling required to collect blood samples. The relationship between cortisol concentrations in circulation with that of blubber and feces, however, is unknown. To assess these associations, we elevated cortisol by orally administering hydrocortisone for five days in five bottlenose dolphins. Voluntary blood and fecal samples were collected daily; blubber biopsies were collected on day one, just prior to hydrocortisone administration, and days three and five of hydrocortisone administration. We evaluated subsequent changes in several circulating stress hormones as well as cortisol and glucocorticoid metabolites in blubber and feces, respectively. There was a significant association between cortisol levels in serum and in blubber (F1,12.7 = 14.3, P < 0.01, mR2 = 0.57) despite substantial variability in blubber cortisol levels. Counterintuitively, fecal cortisol metabolite levels were inversely related to serum cortisol. The relationship between serum and blubber cortisol levels suggests blubber samples from remote sampling may be useful to detect stress loads in this species.

Rapid and reliable steroid hormone profiling in Tursiops truncatus blubber using liquid chromatography tandem mass spectrometry (LC-MS/MS)

“…The combination of improved detection, reduction of noise, and better RSD led to the decision to use a C18 LC separation for the corticosteroids. Using this combination of separations, all RSDs were comparable to ELISA techniques [8, 9, 13] with the added benefit that multiple steroids can be analyzed simultaneously.…”

“…Models on stress built by Champagne et al reported a R 2 value of only 57% between blood and blubber cortisol [13]. In other vertebrates, adipose tissue has been shown to convert cortisol to cortisone and it has been suggested that marine mammal blubber could perform this same conversion [24, 25].…”

“…Testosterone concentrations have been used to determine sexual maturity in males and progesterone concentrations have been used to determine pregnancy in wild-ranging dolphins [8–11]. In addition, there is some evidence that blubber cortisol concentrations could be indicative of stress status in dolphins [12, 13]. …”

Nanospray liquid chromatography/tandem mass spectrometry analysis of steroids from gray whale blubber

“…Data on stress status and reproductive fitness are challenging to obtain in free‐swimming populations of marine mammals but are critically needed for science‐based management and conservation plans. Steroid hormone analyses can provide key information regarding health and fitness and have been conducted previously in marine mammal tissues to determine pregnancy status, male reproductive status, and stress load . While steroid analyses have been conducted in marine mammal blow, feces, and serum, a blubber biopsy is so far the most reliably accessible, and thus suitable, sample matrix that can be collected from free‐ranging animals.…”

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

“…Glucocorticoid hormones (GCs) have been analyzed in several sample types in marine mammals, including blood (i.e., serum, plasma), blubber, feces, hair, saliva, exhaled respiratory 1 vapor ("blow"), cerumen (i.e., earwax, ear plug), and baleen (e.g., Hogg et al 2005Hogg et al , 2009Amaral 2010;Rolland et al 2012Rolland et al , 2017St. Aubin et al 2013;Trumble et al 2013;Hunt et al 2014;Kellar et al 2015;Champagne et al 2016;Robeck et al 2017;Burgess et al 2018). The temporal signature of the physiological response manifested as concentrations of GCs in these different types of biological samples varies from real-time (blood) or near real-time (blow), to hours or days (blubber, feces) or months to years (cerumen, hair, and baleen).…”