Abstract
The processes of lipid deposition and utilization, via the gene leptin (Lep), are poorly understood in taxa with varying degrees of adipose storage. This study examines how these systems may have adapted in marine aquatic environments inhabited by cetaceans. Bowhead (Balaena mysticetus) and beluga whales (Delphinapterus leucas) are ideal study animals—they possess large subcutaneous adipose stores (blubber) and undergo bi-annual migrations concurrent with variations in food availability. To answer long-standing questions regarding how (or if) energy and lipid utilization adapted to aquatic stressors, we quantified variations in gene transcripts critical to lipid metabolism related to season, age, and blubber depth. We predicted leptin tertiary structure conservation and assessed inter-specific variations in Lep transcript numbers between bowheads and other mammals. Our study is the first to identify seasonal and age-related variations in Lep and lipolysis in these cetaceans. While Lep transcripts and protein oscillate with season in adult bowheads reminiscent of hibernating mammals, transcript levels reach up to 10 times higher in bowheads than any other mammal. Data from immature bowheads are consistent with the hypothesis that short baleen inhibits efficient feeding. Lipolysis transcripts also indicate young Fall bowheads and those sampled during Spring months limit energy utilization. These novel data from rarely examined species expand the existing knowledge and offer unique insight into how the regulation of Lep and lipolysis has adapted to permit seasonal deposition and maintain vital blubber stores.
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Acknowledgments
Authors would like to thank the hunters of Barrow Whaling Captain’s Association and the Alaska Eskimo Whaling Commission for allowing collection of samples of their harvested bowhead whales. We also thank the Alaska Beluga Whale Committee and the hunters of Point Lay, Alaska, for allowing the sampling of belugas. In particular, we thank the captains that allowed us to do detailed sampling of their animals. This study could not have been possible without their trust and support. The North Slope Borough and School District provided a great deal of logistical support for fieldwork. Thank you also to Dr. J. Holda and Dr. R. Ramirez for generously providing rodent samples and Cameron Schmidt and Donald Gasper for assistance with data collection. HCB was supported by a Sigma Xi Grants in Aid of Research and two consecutive Choose Ohio First Scholarships; JWP was supported by National Institutes of Health (K01ES025435); JGMT was supported by a grant from the National Science Foundation (34284); RLL supported by National Institutes of Health (DK079282-01A1).
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Ball, H.C., Londraville, R.L., Prokop, J.W. et al. Beyond thermoregulation: metabolic function of cetacean blubber in migrating bowhead and beluga whales. J Comp Physiol B 187, 235–252 (2017). https://doi.org/10.1007/s00360-016-1029-6
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DOI: https://doi.org/10.1007/s00360-016-1029-6
Keywords
- Leptin
- Metabolic activity
- Bowhead whale
- Development
- Blubber