Abstract
Impact of environmental and anthropogenic stressors on the immune system and health of cetaceans is of major concern given the threats of climate change, human activities, and potential exposure to pollutants.1,2 Gene-based health diagnostics has the potential to reveal the physiological response to stressors and impact on health utilizing a minimal amount of blood.3,4 Moreover, while blood is the "gold" standard for assessing health, the ability to gain health information on free-ranging whales from skin biopsies is desired. The overall purpose of this study is to characterize the beluga immune and stress response at the molecular level utilizing blood and skin samples collected in association with different stressors.
Blood samples were collected from aquarium whales before, during, and after veterinary out-of-water examination (OWE), and paired blood and skin samples were collected from wild belugas following live capture-release health assessments (Bristol Bay, Point Lay) and subsistence hunts (Point Lay) in Alaska. Real-time PCR with SYBR-Green technology was used to quantify gene expression of selected markers. The OWE produced variable responses in aquarium whales, suggesting individual coping mechanisms. The pro-inflammatory cytokines IL-2 and IFNγ did not significantly change during the OWE but were significantly up-regulated 1 hour post-OWE, gradually returning to baseline levels within 72 hours. Wild belugas in general showed an activated immune system with increased levels of pro-inflammatory (IL-12, IFNγ, TLR4) and stress markers (AHR, HSP-70) when compared to aquarium whales. However, significant down-regulation of the pro-inflammatory marker IFNγ was observed between pre- and post-examination samples, suggesting immunosuppression. Up-regulation of the toxicology marker AHR in wild belugas in relation to aquarium whales may suggest increased exposure to contaminants in the environment, whereas up-regulation of HSP-70 may indicate increased stress response. Most of the tested immunological markers on blood were also identifiable in skin. This technique only utilizes 2.5 ml of whole blood and looks promising for revealing health information on both aquarium and wild cetaceans. Skin samples will be further investigated for the presence of additional biomarkers, potentially eliminating the need for blood sampling from wild populations.
Acknowledgements
This study was funded by Office of Naval Research (ONR Award no: N00014-14-1-0411). The authors wish to thank Bristol Bay and Point Lay field teams, Bristol Bay Native Association and Mystic Aquarium animal care team, Arctic Coast and research staff for their collaboration and help in sampling. The authors are also thankful to Bristol Bay Marine Mammal Council in Alaska, Dr. Robert Suydam and The Department of Wildlife Management in North Slope Borough.
* Presenting author
Literature Cited
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