Meeting Abstract

113.6  Tuesday, Jan. 7 11:45  Nitrogen solubility related to lipid composition in toothed whale fats LONATI, G.L.*; WESTGATE, A.J.; KOOPMAN, H.N.; UNC, Wilmington; UNC, Wilmington; UNC, Wilmington

Nitrogen (N2) dynamics are physiologically important for air-breathing divers, as N2 inhaled at the surface can saturate fatty tissues that receive blood flow during dives. Toothed whales use cranial acoustic fats to echolocate, but unlike terrestrial mammals, which store fat only as triacylglycerol, acoustic fats also contain wax ester (WE) and unique fatty acids (FAs). As blubber with higher WE content is known to absorb more N2, the highly vascularized acoustic fats may accumulate N2 during dives. We measured and compared tissue lipid composition, percent WE and N2 solubility in blubber and intramandibular (jaw) fat of 3 individuals from each of 3 species: the Atlantic spotted dolphin, Stenella frontalis, and the short-finned pilot whale, Globicephala macrorhynchus (both Family: Delphinidae), and the pygmy sperm whale, Kogia breviceps (Family: Kogiidae). Pig (Sus scrofa) fat was used as a terrestrial comparison. Delphinid jaw fat was dominated (>31% of all FAs) by iso-5:0 – a unique, short-chain FA derived from leucine. Delphinid blubber was the only other tissue that contained iso-5:0 (0.38-4.64%). Kogiid fats contained mostly medium-chain saturated FAs (10:0 through 18:0), and pig fat was largely long-chain saturated FAs (16:0 through 20:0). Percent WE was positively correlated with N2 solubility (P=0.013), although there may be a threshold (~15%) above which increasing WE content does not further affect N2 solubility. For example, N2 solubilities for G. macrorhynchus jaw fat and K. breviceps blubber were 0.0692±0.0004 and 0.0689±0.0010 ml N2/ml lipid, while WE contents were 17.7±1.3 and 98.0±0.7%, respectively. FA profiles may influence tissue gas-loading properties, to compensate for WE content. These data are important for modeling whale diving physiology, as different whale species have different lipid profiles.