Ontogeny and organization of acoustic lipids in jaw fats of the bottlenose dolphin (Tursiops truncatus)

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Zoey Patricia Zahorodny (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Heather Koopman

Abstract: Specialized acoustic fat bodies located around the mandibles of odontocetes have the proposed role of focusing received sound towards the ear. Previous studies have suggested that the distribution of lipids in these fat bodies may form a waveguide for incoming sound. In bottlenose dolphins (Tursiops truncatus) these fat bodies are comprised of triacylglycerols (TAG) and wax esters (WE). Fine-scale topographic distribution and rapid ontogenetic accumulation of branched-chain (iso) fatty acids (FA) in jaw fat and cranial blubber of bottlenose dolphins (n=10) are described here. Iso-acids are unusual endogenous lipids formed as byproducts of amino acid breakdown and have a hypothesized role in sound transmission. Isovaleric acid (i-5:0) is toxic to most mammals, so the considerable presence of this FA in dolphin acoustic tissues represents an unusual physiological trait. Iso-acids were the dominant FA constituents in jaw fat, often comprising up to 80 wt%. Fetal concentration of i-5:0 was extremely low (<3 wt%) compared to adults (up to 52 wt%), and calves and subadults exhibited intermediate values. Little FA variation was found in adult inner jaw fat except for reduced values of iso-acids at the dorsal-most region along the length of the fat body. Adult outer jaw fat had highest iso-acid accumulation over the thinnest region (pan bone) of the mandible, with low iso-acid values at the dorsalmost regions sampled. In all animals, blubber contained very low levels of isoacids. The notable exception was a small area of blubber on the lateral mandibular region overlying Norris’ “acoustic window”. Blubber here exhibited up to a 10-fold increase in iso-acids compared to adjacent blubber. This acoustic window blubber is thus more chemically similar to acoustic mandibular fat, than to body blubber, and likely confers less impedance to sound waves. Young animals showed rapid accumulation of i-5:0 and i-15:0 in acoustic tissues and variation in iso-acid accumulation across age classes was described by logarithmic curves which accounted for upwards of 68% of variation. Patterns of lipid distribution of inner and outer jaw fat were apparent in animals as young as calves, while patterns were apparent in cranial tissues even earlier; at the fetal stage.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
Language: English
Date: 2009
Bottlenose dolphin--Morphology, Bottlenose dolphin--Physiology, Lipids--Research
Bottlenose dolphin -- Physiology
Bottlenose dolphin -- Morphology
Lipids -- Research

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