Solubility of nitrogen in marine mammal blubber depends on its lipid composition

• Published in: Journal of Experimental Biology
• Main Authors: Koopman, Heather N., Westgate, Andrew J.
• Format: Text
• Language: English
• Published: Company of Biologists 2012
• Subjects: Research Article; toothed whale; toothed whales
• Online Access: http://jeb.biologists.org/cgi/content/short/jeb.074443v1; https://doi.org/10.1242/jeb.074443

Understanding the solubility of nitrogen gas in tissues is a critical aspect of diving physiology, especially for air-breathing tetrapods. Adipose tissue is of particular interest due to the high solubility of nitrogen in lipids. Surprisingly, nothing is known about nitrogen solubility in the blubber of any marine mammal. We tested the hypothesis that N 2 solubility is dependent on blubber's lipid composition; most blubber is composed of triacylglycerols, but some toothed whales deposit large amounts of waxes in blubber instead. The solubility of N 2 in the blubber of 13 toothed whale species ranged from 0.062-0.107 mL N 2 /mL oil. Blubber with high wax ester content had higher N 2 solubility, observed in the beaked (Ziphiidae) and small sperm (Kogiidae) whales, animals that routinely make long, deep dives. We also measured nitrogen solubility in the specialized cranial acoustic fat bodies associated with echolocation in a Risso's dolphin; values (0.087) were 16% higher than its blubber (0.074). As the acoustic fats of all Odontocetes contain waxes, even if the blubber does not, these tissues may experience greater interaction with N 2 . These data have implications for our understanding and future modeling of, diving physiology in Odontocetes, as our empirically derived values for nitrogen solubility in toothed whale adipose were up to 40% higher than the numbers traditionally assumed in marine mammal diving models.