Bottlenose Dolphin (Tursiops truncatus) as a Model to Understand Variation in Stress and Reproductive Hormones Measures in Relation to Sampling Matrix, Demographics, and Environmental Factors.

摘要

Our overarching goal is to develop indicators and methods to quantify chronic stress in bottlenose dolphins. Much research has focused on the stimuli which induce stress in marine mammals, as well as the hormonal mediators of the stress response. Stress may be induced by a variety factors, including noise, pollutant or toxin exposure, presence of predators, loss of prey, and/or habitat changes. The stress response is complex and difficult to study experimentally in marine mammals due to ethical and logistical considerations, but has been well characterized in other laboratory mammal species. In mammals (including marine mammals) and other vertebrates, the stress response has two modes of operation: 1) the fast mode involves the rapid release of fast-acting agents that drive the fight-or-flight response, such as catecholamines, which excite the hypothalamic-pituitary-adrenal (HPA) axis and initiates a hormonal cascade that ends in the secretion of glucocorticoids (GCs) by the adrenal cortex; and 2) the delayed but more sustained response driven by GCs that coordinates brain and body functions to cope with stress and facilitate recovery, adaptation, and re-establishment of homeostasis. While the HPA axis and physiological processes driven by the GCs are essential for an individual s ability to respond and adapt to stress, prolonged elevation of GC hormones can lead to chronic immune suppression and inhibition of other energy-expending hormonal systems, including disruption of reproductive function along the HPA axis, all of which may cumulatively lead to decreased survival and/or inability to reproduce. For this reason, developing indicators and methods to quantify stress in marine mammals is essential for understanding risks and long-term consequences for populations.