Meeting Abstract
Diving marine tetrapods experience physical variation in their environments (i.e. decreased temperature and increased pressure), which introduces significant physiological challenges. Adipose tissue is of particular concern for diving physiology, because N2 gas is 5 times more soluble in fat than water/blood. Therefore, at any blood/tissue interface, gas will diffuse from blood into tissue, potentially increasing the risk of decompression sickness. Exposure of tissues to N2 gas is a function of pressure, N2 solubility, blood flow, and the number of blood vessels. Interestingly, the microvascularity (e.g. capillaries, microarterioles and microvenules) and the N2 solubility of the adipose tissue of diving tetrapods have never been examined. Percent microvascularity was determined by incubating frozen sections from terrestrial mammals (Sus scrofa, Ovis aries, Capra aegagrus hircus, Bos taurus) and diving tetrapods (Hippopotamus amphibius, Dermochelys coriacea, Caretta caretta, Somateria mollissima, Phygoscelis adeliae, Balaenoptera acutorostrata, Balaenoptera borealis) in a solution of NBT/BCIP to stain for endogenous alkaline phosphatase. Nitrogen saturation (as measured by our previously described apparatus) does not differ across taxa. In contrast, there is considerable variation in microvascular density across species. Percent vascularity ranges from 0.81 to 5.40% in terrestrial mammals and 2.03 to 8.12% in diving tetrapods, indicating the potential for gas exchange. Preliminary analysis suggests that the fatty acid profiles and fatty acid chain lengths may further help to distinguish which taxa may be more at risk of decompression sickness.
