Abstract
Isovaleric acid (iso5:0) is an unusual fatty acid that is important for echolocation and hearing in acoustic tissues of some odontocetes, but its functional significance in blubber is unknown. We examined patterns of accumulation of this compound in blubber in 30 species of odontocetes (n = 299). Iso5:0 concentrations in blubber varied with phylogeny, ontogeny and body topography. Iso5:0 accumulated in greater quantities in superficial/outer blubber than in deep/inner blubber. In the outer blubber of northern right whale and Hector's dolphins, iso5:0 accounted for one-third to one-half of all fatty acids. Total blubber burden of iso5:0 in harbour porpoises represented up to 15 times the amount deposited in the melon. The composition of the melon does not change during starvation in harbour porpoises, supporting the hypothesis that lipids in melon are conserved for a specific function. Some odontocetes continually deposit iso5:0 in blubber after levels in melon have reached asymptotic levels, suggesting independent control of iso5:0 synthesis and storage in these compartments. Dolphins and porpoises inhabiting cold waters possess higher concentrations of iso5:0 in their outer blubber layers than species from warmer regions. We propose that this relationship represents an adaptive secondary role for iso5:0 in maintaining blubber flexibility in cold environments.
| Original language | English |
|---|---|
| Pages (from-to) | 247-261 |
| Number of pages | 15 |
| Journal | Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology |
| Volume | 173 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Apr 2003 |
Bibliographical note
Funding Information:Acknowledgements We wish to thank many individuals and organisations for their generosity in contributing samples and assisting with sample collection: Bill McLellan and Ann Pabst (University of North Carolina at Wilmington; John Nicolas (National Marine Fisheries Service, Northeast Fisheries Science Center); Charley Potter (National Museum of Natural History, Smithsonian Institution); Thomas Jefferson and Susan Chivers (NMFS, Southwest Fisheries Science Center); Ellie Dickson and Elizabeth Slooten (University of Otago); Koen van Waerebeek and Julio Reyes; and many people from: state stranding networks from Massachusetts to Florida; Virginia Marine Science Museum; Hubbs-Sea World, Orlando, Florida; Mote Marine Laboratory, Sarasota, Florida; the Beaufort, North Carolina and Woods Hole, Massachusetts NMFS offices; the Marine Mammal Stranding Program at UNCW; the Duke University Marine Laboratory, Beaufort, North Carolina; the Canadian Department of Fisheries and Oceans; the Grand Manan Whale and Seabird Research Station, New Brunswick, Canada; and the fishermen of the Bay of Fundy and Gulf of Maine. This manuscript was improved by the comments of Ann Pabst and Kay Tanaka, and we also thank Dr. Tanaka for useful insights into, and suggestions regarding, iso5:0 metabolism. Samples were imported into Canada and the United States of America under appropriate CITES and US Department of Fish and Wildlife permits, and all analytical methods complied with current US and Duke University regulations. This study was supported by postgraduate fellowships from the Canadian Natural Sciences and Engineering Research Council (NSERC) and the Duke University Marine Laboratory to H.N.K., a postdoctoral scholarship at Woods Hole Oceanographic Institution to H.N.K., a Duke University Marine/Freshwater Biomedical Center Feasibility Study grant to H.N.K. and A.J.R., and NSERC Research and Equipment Grants to S.J.I. This represents Woods Hole Oceanographic Institution contribution number 10683.
ASJC Scopus Subject Areas
- Ecology, Evolution, Behavior and Systematics
- Biochemistry
- Physiology
- Animal Science and Zoology
- Endocrinology